Advances in Corrosion Control Coating Technology A … · CORROSION CONTROL COATING TECHNOLOGY ......

ADVANCES IN CORROSION CONTROL COATING TECHNOLOGY

A JPCL eBook

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Advances in corrosion control coating technologyA JPCL eBook

Copyright 2011 - 2015 byTechnology Publishing Company2100 Wharton Street, Suite 310

Pittsburgh, PA 15203

All Rights Reserved

This eBook may not be copied or redistributed without the written permission of the publisher.

i

© 2011-2015 Technology Publishing Co.

Introduction

FEVE Technology for Higher Performance Coating Systems on BridgesBob Parker, AGC Chemicals Americas

Titans of the Abyss: Polyurethane, Polyurea, and Hybrid Lining TechnologyMike O’Donoghue Ph.D. and Vijay Datta MS, International Paint LLC

Paint & Coatings—Where Are We Now?Brian Goldie, JPCL

Improving Polyurethane Pipe Coatings for Harsh ConditionsAndreas aus der Wieschen, Matthias Wintermantel, Todd Williams and AhrenOlson, Bayer MaterialScience AG

Raw Material Suppliers Answer Calls for Green and Smart CoatingsBrian Goldie, JPCL

Contents

iiContentsSPONSORED BY

1iv

6192430

®

FEVE RESIN


iv

Introduction

Introduction

This eBook features articles from the Journal of Protective Coat-ings & Linings (JPCL) about technological advancements inheavy-duty coatings for corrosion control.

©iStockphoto/Bim


FEVE Technology 1

FEVE Technology for Higher Performance Coating Systems on Bridges

he history of coating system types used on steel bridges has always paralleled the evolution

of coatings technology as a whole. When breakthroughs have occurred, the bridge coating

market has paid attention and embraced these advancements. Sometimes, regulations have

played a significant part in altering this course of evolution, but the goal of the stewards responsible for

bridge maintenance and preservation has never changed. The ideal coating system will always be the

one that offers the best protection of the substrate at a reasonable cost, with due respect for compli-

ance with regulations.

The most popular long-life coating system in place at this time for bridges with challenging applica-

tions and environments is a three-coat system consisting of a zinc-rich primer, an epoxy midcoat and a

polyurethane topcoat. Other less expensive coating systems still exist, but many provide lesser protec-

tion and have a shorter lifetime. Depending on the available funding for any specific bridge project,

these options may be the only choice. However, if the goal of the bridge steward is the ultimate protec-

tion of the bridge against structural degradation for the longest period of time, the standard three-coat

system is the preferred choice.

Fluoroethylene vinyl ether (FEVE) fluoropolymer technology has proven to be a successful addition

to the global bridge coating market (Fig. 1). In the U.S., there is a growing interest from state DOTs,

TBy Bob Parker,AGC Chemicals Americas

Fig. 1: The Swan Bridge in Muroran, Japan, is one of many bridges worldwide that has seen a longer life cycle thanks to its FEVE resin-based topcoat. All photos and figures courtesy of AGCChemicals Americas, Inc.


local municipalities and the private sector

(Fig. 2). The discussion of the life cycle of a

coating system has paved the way for this

growing interest, as the cost of coating a

bridge decreases dramatically when it is

based on the lifetime of the coating system.

When the life cycle costs of bridge painting

and maintenance are taken into account,

then the use of fluoroploymer coatings be-

comes cost effective.

This article will discuss the chemistry be-

hind FEVE technology, coating types that

can be formulated with FEVE resins, and

the performance of FEVE-based coatings

used as topcoats on steel bridges.

FEVE Resin StructureFEVE technology is most effective when incorporated into the aforemen-

tioned three-coat system. The FEVE polyol resins play an integral part in

the topcoat layer, replacing the standard acrylic or polyester polyols as

the principle binder. This technology has been commercial since 1982

and has been used on bridge coating systems across the globe since its

introduction. The key performance improvements of the FEVE polyol

resins over traditional polyesters are their resistance against UV degra-

dation and their resistance to moisture permeation. The structure of the

resin’s backbone is illustrated in Figure 3.

The uniqueness of this resin lies in the combination of fluoropolymer chemistry with vinyl ether chem-

istry, allowing both chemistries to bring their respective strengths to the polymer’s performance. With-

out the presence of fluorine, the polyol would lack its superior weatherability and resistance properties.

Without the vinyl ether, the common properties of most organic resins — solubility in solvents, available

functional groups, and adjustability of the glass transition temperature (Tg) — would be absent and the

resin could not function in liquid coatings.

Coating Formulations with FEVE ResinsAs with any coating, the performance of the finished product is dependent on many factors. Each raw

material plays a part in either improving or weakening the coating’s performance. When an FEVE

polyol is part of a formulation, it can only benefit from the careful choice of other components in the for-

mulation. The whole concept of creating a coating that will endure for many years necessitates consid-

eration of every ingredient in the coating to be the best choice for weatherability and resistance

properties. There can be no weak link in the chain.

Several types of coatings can be produced with FEVE resin technology. The original coating in

1982 was a solvent-based, two-component finish that used an aliphatic polyisocyanate as the

cross-linker. It strongly resembled conventional polyurethane finishes in curing behavior and

methods of application. This system cures and applies just like a conventional polyurethane fin-

ish, but with far superior exterior durability. This coating type is still the fluorinated topcoat of

choice on bridges. VOC regulations in certain regions of the U.S. have made reformulation nec-

essary, but the availability of solid FEVE resins and their ability to dissolve in VOC-exempt sol-

2

Fig. 3: This graphic illustrates the structure of the FEVE resin backbone. Thefluorinated segments (blue) provide weatherability and chemical resistance;the vinyl ether segments (green) provide gloss, solubility and crosslinkingproperties; and the R groups provide OH functionality, flexibility and adhesion.

Fig. 2: FEVE resin-based coatings are becoming more widely accepted for bridges in the U.S., including theGateway Bridge in Nashville, Tenn.


vents have preserved the presence of this

technology to date.

In 2012, a water-based FEVE polyol disper-

sion entered the coatings market. This resin uti-

lizes water-emulsifiable aliphatic polyisocyanates

as its cross-linking partner. Up to now, water-

based, two-component polyurethane technology

has not been widely accepted in the bridge coat-

ing market, due to the increased sensitivity to at-

mospheric conditions like temperature and

humidity when these coatings are applied. Con-

sequently, this resin has only been tested in labo-

ratory trials. To date, the advantages of FEVE

water-based resin chemistry are only being real-

ized in factory-applied finishes for prefabricated

bridge components, where the reduction in VOCs

will improve the air quality of the interior working

space.

A third FEVE resin type, a water-based emul-

sion synthesized to a high molecular weight, is

available for use in one-component coatings for

bridges. Several DOTs across the country have

incorporated one-component, water-based coat-

ings, which are predominantly acrylic-based. Ex-

tensive lab work has been completed in the

testing of topcoats that contain FEVE emulsions.

Due to the strict limitations in cost dictated by the

current price range of the acrylic-based coatings

that have penetrated this market, most of the

FEVE emulsion-containing formulations use both

FEVE emulsions and acrylic emulsions as the

binder portion. Performance improvement has

been evident in formulations utilizing 20 to 50 per-

cent FEVE emulsion as the binder, depending on the particular color.

It is prudent to mention the mechanism by which FEVE resins resist degradation by UV

radiation. FEVE resins do not absorb the sun’s UV radiation. Without absorption, no exci-

tation of the FEVE chemical bonds can occur, and the resin basically remains unchanged.

This is the key to the superior durability of FEVE resins. Accordingly, since they do not ab-

sorb the light, they cannot block it either. This is an important point to consider when formulating a

FEVE-based coating. UV absorbing and light stabilizing additives must be formulated into FEVE

resin-based clear coatings to protect any base coating to which it is applied. The most popular addi-

tives are the organic UV absorbers and hindered amine light stabilizers available on the market. To

expand on this any pigmented FEVE resin-based formulation will also be improved with the use of

UV light-stabilizing additives. These additives can extend the lightfastness of pigments, which al-

lows coatings systems to remain robust against UV degradation.

3

Fig. 4: This graph compares two different FEVE resin-based coatings against two other popular bridge top-coats. The coatings were tested inside of a QUV weatherometer for 3,000 hours, and the two FEVE-basedcoatings showed significantly better gloss retention percentages than the other coatings tested.

Fig. 5: This graph compares the gloss retention of a FEVE resin-based coating against a PVDF polyurethanecoating and a standard acrylic-urethane bridge topcoat. As the exposure to UV light increased, the FEVEcoating again displayed the best gloss retention percentage.

Table 1: Results of FEVE Topcoat Application on Tokiwa Bridge

Initial Final Gloss Color

60°�Gloss 60°�Gloss Retention (%) Change (∅E)

75 69 91 3.5


Performance PropertiesBoth accelerated exposure testing and real-life exposure testing have been per-

formed on coatings using FEVE technology. Figures 4 (p. 40) and 5 show com-

parisons of FEVE resin-based coatings with different coatings also used as

topcoats for bridge coating systems.

The graph in Figure 4 shows two different FEVE resin-based coatings — a

100% FEVE polyol, and a 78% FEVE polyol blended with 22% polyester polyol.

FEVE solvent-based resins, like the FEVE emulsions, have a wide range of com-

patibility with other polyols. Laboratory work is being done to measure the per-

formance capabilities of these blended formulations. Some physical properties of

the paint film, such as flexibility, can be improved when non-FEVE polyols be-

come part of the formulation. As this graph shows little change with the 60-de-

gree gloss at 3,000 hours, the exposure is still in progress.

The second test exposure was done at the Equatorial Mount with Mirrors for

Acceleration with Water (EMMAQUA) test site in Arizona (Fig. 5). The meas-

urement of UV exposure is in megajoules per square meter (MJ/m2). Again,

the FEVE coating showed the best gloss retention percentage of all the coat-

ings tested.

Certain bridge applications are being monitored for their performance. The

The Tokiwa bridge is located in Japan (Fig. 6). This bridge was recoated in

1986, using two coats of an epoxy primer and two coats of a FEVE-based top-

coat. The changes in 60-degree gloss and color over 25 years of exposure are

shown in Table 1 (p. 3).

Additional ConsiderationsBecause the main function of FEVE resin-based coatings is to extend the life of

the coating system, it is important to point out other proposals for bridge coating

longevity that should to be considered in order to achieve this goal. Some

thought has been given to expanding the procedure for coating a bridge so that

the critical components of the bridge get the best protection from the coating sys-

tem. Conversely, the remaining components, which are not prone to early coating

failure, can be given a lesser degree of protection. This idea is explained in detail

in a JPCL article written in 1984 by Clive Hare, entitled “Specific Utility In the De-

sign of Coating Systems for Steel Bridges.” Hare states that, “The ever-increas-

ing demands on bridge paint systems (fed by increasing traffic loadings, salt

usage, and years of neglect) must be met by the use of heavier duty coating sys-

tems applied with great exactitude over better surfaces.”

The article goes into detail about specific areas of bridges that have historically

experienced premature coating failure resulting in damaging corrosion of the

steel. The seams, edges, bolts and rivets of bridges are most susceptible (Fig. 7).

These are the areas that need coating systems that are more functional for corro-

sion resistance. In many instances, these areas do not receive the level of UV radiation experi-

enced by other parts of the bridge, but the need for recoating is still critical.

The use of a FEVE resin-based topcoat has demonstrated the ability to resist the penetration

of chloride ions through energy-dispersive X-ray microanalysis testing. However, the difficulty of

attaining success lies in the morphology of certain bridge components and the challenge of

coating application on these components. Although FEVE technology can offer greater

44

Fig. 6: These photos show the Tokiwa Bridge in Japan, which wascoated with a FEVE-based topcoat in 1986. The photo on the topwas taken in 1988, the middle photo in 1993, and the photo onthe bottom in 2014. Clearly, there has been very little change inthe coating's gloss and appearance over the years.


longevity of the topcoat on a bridge, the protection of every steel surface, for up to thirty years,

is still a significant challenge.

ConclusionAlthough FEVE technology has shown itself as a viable alternative to standard topcoats for the

three-coat system for bridges, research is continuing on the utilization of this technology in

combination with zinc-rich primers or epoxy primers to create an effective two-coat system.

The elimination of an entire coat will significantly lower the final cost of the coating project.

As the evolution of coatings for bridges continues, the ultimate goal will always be the most

efficient protection of the steel substrate at the most reasonable cost. If we can succeed in pro-

longing the life of an important part of our nation’s infrastructure, much will be gained from this

success.

About the AuthorBob Parker is a technical service chemist for AGC Chemicals Americas in Exton, Pa. He has been

involved in formulating paints and coatings for over 30 years. He received his Bachelor of Science

degree in chemistry from Alvernia College. He is currently responsible for technical service for

LUMIFLON fluoropolymer resins in the U.S.

5

JPCL


Fig. 7: Certain bridge components such asseams, edges, bolts and rivets still presentcoating and life cycle challenges, even forFEVE-based coatings.

Titans of the Abyss: Polyurethane, Polyurea, and Hybrid Lining Technology

Lining Technology 6

By Mike O’Donoghue Ph.D. and Vijay Datta MSInternational Paint LLC

he demand for enhanced productivity, cost reduction, fast throughput, and optimization of

life cycle costs associated with high-performance lining applications is often met using

two-component, solvent-free polyurethane, polyurea, and polyurethane/polyurea hybrids.1-3

Moreover, these thermoset technologies can readily comply with today’s stringent environmental regu-

lations, as exemplified by their low- or zero-VOC content and absence of oxygen-depleting substances

(ODSs).

The genesis of polyurethanes hails back to the pioneering work on isocyanates by Otto Bayer in

1937. As a result of Bayer’s work, thin-film polyurethane finish coats later became for decades the de

facto finish coat of choice on structural steel. It was not until the early 1980s when thick-film and single-

coat solvent-free aromatic polyurethane linings were formulated

for use on girth welds, valves, and pipe. By the mid-1980s, ad-

vanced versions of these polyurethane linings were being used on

large-scale pipe rehabilitation projects in Western Canada.4 Then,

by the late 1980s, an innovative generic class of thick-film and sin-

gle-coat solvent-free coatings and linings emerged on the

scene—polyureas.5–7 Like their fast-reacting and fast-curing

polyurethane predecessors, the even faster gel time and cure time

of the polyureas necessitated that these linings be applied by plu-

ral-component spray equipment.

In the early 1990s, further advances led to new and improved

polyurethane and polyurea linings in which properties could be

customized. Later, various hybrids of both technologies were de-

veloped and touted by some to have a combination of the best

properties of multiple technologies.8 Interestingly, many of today’s

so-called polyurethanes are actually hybrids, and the implied ter-

minology distinctions among polyurethane, polyurea, and

polyurethane/polyurea hybrid descriptions has become somewhat

blurred.9 For example, a coating may be described as a

polyurethane, but it is actually a hybrid.

This article will focus primarily on very fast-cure, solvent-free

polyurethanes, polyureas, and polyurethane/polyurea hybrid tech-

nologies, many of which are well-suited to immersion service: the

veritable Titans of the Abyss.

The chemistry, cure mechanism, safety aspects, strengths, and

weaknesses of each technology will be discussed. Case histories

will be provided for each technology.

In today’s fast-track lining projects, the gel time and cure time of

a given lining might vary from a few seconds to a few hours. Coat-

T

© istockphoto.com/whitphotography © 2011-2015 Technology Publishing Co.

ing formulators and polymer chemists can utilize these technologies to carefully tailor elas-

tomeric or high-tensile strength rigid linings for specific tank and pipe internals or externals.

Depending on the chemistry of a polyurethane, polyurea, or hybrid, the applications for

these linings are diverse.

Examples of applications include the following:

• penstocks, riveted and welded;

• potable water processing, transportation, and storage;

• aquariums;

• pipelines exposed to raw sewage and erosion degradation;

• concrete digesters;

• cooling water intakes;

• primary and secondary containment;

• rail cars;

• oilfield pipelines;

• icebreakers (underwater hulls);

• platforms;

• barges;

• syntactic foams for sub-sea projects;

and

• food storage.

Each service represents conditions in which one or more factors, such as corrosion and

7

Fig. 1: Polyurethane formation

Fig. 2: Polyurea formation

erosion resistance, flexibility, immersion resistance, and wear resistance are important. All three lining

technologies have been used on carbon steel, galvanized steel, ductile iron, and concrete substrates.

Lining Selection: The Influence of Chemistry in Polyurethane, Polyurea, and HybridsCommon to the polyurethane, polyurea, and hybrid linings is the use of an isocyanate component in the

cure reaction.10

Essentially, the film formation of a polyurethane lining stems from the reaction of isocyanate groups (-

NCO) with hydroxyl groups (-OH moieties) in a polyol (Fig. 1). At least one catalyst is normally used to

improve the reaction of the isocyanate and hydroxyl groups.

In contrast, in the film formation of a polyurea lining, the isocyanate groups react with an amine group

(e.g., -NH2). A catalyst is not used in this reaction (Fig. 2).

Case History: Paper Mill Wastewater Treatment Clarifier, U.S. In 1996, a newsprint mill in the U.S. discovered that the concrete structures of its wastewaterclarifier, particularly the walls, were experiencing extensive corrosive attack from hydrosul-furous acid, sulphuric acid, and hydrogen sulphide.21

The corrosion had resulted in exposed rebar, and aggregate protruded up to a half-inch incertain areas. Approximately 10,000 square feet required refurbishment.Within 72 hours, the concrete walls and steel center (including rakes) were abrasive blasted

and respectively lined with 125 mils’ DFT and 60 mils’ DFT of a 100%-solids polyurethane lin-ing.After five years, the clarifier was drained, and the linings were inspected. The linings were

found to be completely intact on the entire 10,000 square feet of surface (See photo aboveand on p. 48).The rapid productivity associated with this one-coat lining installation, coupled with the out-

standing performance in immersion, was lauded by the owner of the facility.

Polyurethane lining in paper millwastewater treatment clarifier21

(concrete substrate)


As expected by the term “hybrid,” in the film formation of a hybrid lining,

both the isocyanate-polyol and isocyanate-amine reactions occur. The re-

action rate and concentration of urethane or urea linkages depend on the

proportion of polyurethane to polyurea in a given hybrid formulation as

well as the usual consideration of stereochemistry of the reaction part-

ners and number of reactive groups. As with polyurethanes, a catalyst is

invariably used to control the reaction with hybrids.11

Because the reaction rates of water and isocyanates and of polyols and

isocyanates are typically within an order of magnitude of one another, it is

critical to ensure that water does not contact the isocyanate in a

polyurethane lining application. Should water contact the isocyanate, a

cross-interference reaction will take place and the polyurethane structure

will be compromised. An unstable carbamate will form and decompose to

carbon dioxide and an amine (Fig. 3). By way of comparison, the reaction

rates of water and isocyanates are many orders of magnitude less than

the reaction rates of amines and isocyanates; thus, polyurea and hybrid

applications are far less sensitive to moisture.5

The chemical, mechanical, and thermal properties of each of these lin-

ings depend on the chemical makeup of the raw materials, the type and

strength of the chemical bonds, the spatial configuration and steric hin-

drance of organic substituents on certain atoms, the resultant molecular

linkages in the polymer film, and the ultimate ingenuity of the lining for-

mulator.

Although performance in various services can vary markedly, these lin-

ings, as a whole, have excellent barrier properties and interpose a high

electrical resistance into a corrosion cell circuit.

DefinitionsIn terms of chemistry and cure mechanism, a more thorough definition of polyurethane, polyurea, and

hybrid technology is available from the Polyurea Development Association.12

Polyurethane: “For reference purposes, a polyurethane coating/elastomer is that derived from the

reaction product of an isocyanate component and a resin blend component. The isocyanate can be

aromatic or aliphatic in nature. It can be a monomer, polymer, or any variant reaction of isocyanates,

quasi-prepolymer, or a prepolymer. The prepolymer, or quasi-prepolymer, will be made from hydroxyl-

terminated polymer resins.

“The resin blend must be made up of hydroxyl-terminated polymer resins, being diol-, triol-, or multi-

hydroxyl polyols, and/or aromatic or aliphatic hydroxyl-terminated chain extenders. The resin blend

may also contain additives, or non-primary components. The resin blend will contain catalyst(s) for sys-

tem reactivity.”

Polyurea: “A polyurea coating/elastomer is that derived from the reaction product of an isocyanate

component (as described for a polyurethane) and a resin blend component. The isocyanate can be

aromatic or aliphatic in nature.

“The resin blend must be made up of amine-terminated polymer resins, and/or amine-terminated chain

extenders. The amine-terminated polymer resins will not have any intentional hydroxyl moieties. Any hy-

droxyls are the result of incomplete conversion to the amine-terminated polymer resins. The resin blend

may also contain additives, or non-primary components. These additives may contain hydroxyls, such as

pre-dispersed pigments in a polyol carrier. Normally, the resin blend will not contain a catalyst(s).”

8

Fig. 3: Formation of carbamic acid

Fig. 4: Structures of various polyols


9

Hybrid: “For reference purposes, a

polyurethane/polyurea hybrid coating/elastomer

is the reaction product of an isocyanate compo-

nent (as above) and a resin blend component.

“The resin blend may be made up of blends of

amine-terminated and/or hydroxyl-terminated

polymer resins, and/or amine-terminated and/or

hydroxyl-terminated chain extenders. The resin

blend must contain blends of amine-terminated

and hydroxyl-terminated moieties. The resin

blend may also contain additives, or non-primary

components. The resin blend may contain cata-

lyst(s) for system reactivity.”

Table 1 shows the reactions of the isocyanate

group with various hydrogen donating groups

and the resulting structures obtained.2

Polyurethanes: Film FormationFigure 4 (p. 45) shows structures of polyether

and polyester polyols. Some of these polyols

may be used to react with an isocyanate compo-

nent such as straight methylene diisocyanate

(MDI) or a quasi-prepolymer derived from MDI it-

self. Figure 5 (p. 48) shows a typical structure of an isocyanate component used in

the film formation of a solvent-free, single-coat aromatic polyurethane lining.

Figure 6 (p. 48) is an oversimplified representation of the micro-structures of

polyurethane elastomers and the high-tensile strength, rigid, and hard

polyurethane linings. In the polymer network, the polyurethane exhibits a two-

phase morphology consisting of soft and hard segments.13 The soft segment is be-

cause of the long-chain, high-molecular weight polyether or polyester polyols,

which are relatively non-polar, whereas hard segments consist of the diisocyanate

and short-chain, low-molecular weight chain extender(s), which are relatively polar.

The chemical stability and physical characteristics of a polyurethane film are de-

rived from the chemistry of the individual components. Generally, polyester-based

polyurethanes are more resistant to oil, grease, solvents, water, UV, ozone, and

wear, whereas polyether polyurethanes are more resistant to hydrolysis, low tem-

perature flexing, and microbes/fungus. Tailoring the chemical resistance and physi-

cal properties of a given polyurethane system can be accomplished by adjusting

the ratio of hard and soft segments and the amount of chemical cross linking. In-

creasing the hard-segment concentration and cross linking of the system results in

harder polymers that are generally more chemically and hydrolytically stable than

soft polymers because the hard segment is hydrophobic and less rapidly at-

tacked.13,14 Conversely, a high soft-segment concentration and low cross link den-

sity will produce a softer, more elastic polyurethane.

When a polyurethane coating is engineered to be an “under cross linked” film

(NCO:OH <1), the film typically will be more flexible and less resistant to solvent

and chemicals. In comparison, the same system formulated to produce an “over

Table 1: Reactions of the Isocyanate Group2

Hydrogen Donor General Reaction Product ClassStructure Product Structure

Water H2O + RNCO Amines + RNH2 + H2Ocarbon dioxide (RNHCONNR)(leading to

disubstituted urea)

Hydroxyl groups R1OH + RNCO Urethanes RNHCOOR1

Amine groups R1NH2 + RNCO Disubstituted RNHCONHR1

ureas

Disubstituted R1NHCONHR2 + RNCO Substituted R1NHCONR2CONHR3

ureas biurets

Urethane R1NHCOOR2 + RNCO Allophonates R1NHCOHR2COOR2

Carboxylic acids R1COOH + RNCO Amides RNHCOR1

Isocyanates will also react well with the following less common hydrogen donors.

Imino groups - NH Sulfonamide groups - SO2NH2Substituted amine groups - NHR Sulfonamides - SO2NHR

Carbonamide groups - CONH2 Thioamide groups - SHNR2Substituted carbonamides - CONHR Sulphonic acid groups - SO2OH

Sulfhydryls - R1SH

Fig. 5: Structure of isocoyanates(example: MDI methylene diphenylisocyanate)

Fig. 6: Two-phase morphology:hard and soft segments in polyurethanes


cross linked” film (NCO:OH >1) will yield a

harder and more chemical-resistant film.

Aromatic isocyanate groups are far more reac-

tive than aliphatic isocyanate groups in polyiso-

cyanates. Consequently, linings derived from

aromatic diisocyanates, for example, dry and

cure faster than comparable systems based on

aliphatic isocyanates. The high viscosity of the

polyol and isocyanate components, in addition

to fast set times, necessitate the use of plural-

component spray equipment. (However, repair kits of polyurethane linings are available for use on

touch-up joints and connections).

A later development to thick-film aromatic polyurethane linings has been the advent of high-solids,

aliphatic polyurethane coatings.15 In essence, three approaches were used to commercialize high-per-

formance, solvent-free aliphatic polyurethane linings:

• low molecular weight compounds with lower viscosity,

• reactive diluents, and

• new polyurethane prepolymers.

While aliphatic systems are of great interest, less expensive, higher performing aromatic

10

Rapid productivity in shop and field applications, e.g., pipelines

Elimination of solvents and compliance with stringent air pollution regulations (VOCs)

Single coat, high-build applications up to 250 mils (~6,000 microns)

Formulated in a broad spectrum of cure times—minutes to hours

Rapid curing even at sub-zero temperatures

Formulation diversity based on vast selection of polyol and isocyanate raw materials

Customized water and chemical resistance, flexibility, and impact resistance

Coated pipes are readily inspected and buried within minutes of application

Low surface friction—excellent hydraulic characteristics for pipeline internals

Good cathodic disbondment resistance at temperatures below 50 C

Can be used with geotextiles

Abrasion resistance can be superior to AR steel

Repairable by hand within minutes (kits available)

Advantages of Polyurethane LiningsDisadvantagesof Polyurethane Linings

Moisture sensitivity—susceptibility to thickening, gelation, and foaming

Relatively low alkali and solvent resistance

Potential allergic reactions due to any free isocyanate content

Susceptible to undercutting and peeling when immersed linings are mechanically damaged when not formulated properly for this service

Poor cathodic disbondment resistance at temperatures above 50 C

Poor hot water adhesion

Poor color retention in aromatic polyurethanes with UV exposure

Polyurethane lining in paper mill wastewater treatmentclarifier21 (steel substrate)

Fig. 7: Structure of amine resin in a polyurea


polyurethanes are used for immersion service.

In terms of rapid throughput of lined pipes, for example, in shop applications or pipe rehabilitation

projects, the fast-set and rapid-cure characteristics of polyurethane linings are highly advantageous,

saving both time and money. (Some advantages and disadvantages of polyurethane linings are listed

on p. 48).

Polyureas: Film FormationTypical structures of amine resins are shown in Fig. 7. To form urea linkages, and thus polyurea linings,

extremely fast cross linking occurs through the isocyanate/amine-terminated resin (Fig. 2.) According

to the PDA, the resulting polymer is termed a “pure polyurea.”

Rapid set times of less than one minute and a cure reaction largely unaffected by atmospheric mois-

ture are features synonymous with two-component polyurea linings. Therefore, in terms of time, project

costs, and overall productivity, the fast-set and rapid-cure characteristics of polyurea linings are highly

advantageous, both in shop applications and field work where quick returns to service are critical.

As with solvent-free polyurethane linings, in the

polymer network of a polyurea lining, there is two-

phase morphology consisting of soft and hard seg-

ments. The isocyanate component is often a

quasi-prepolymer derived from MDI. Given that

polyurea, polyurethane, and hybrid coatings can

have similar structural backbones, it is not surpris-

ing that versions of each lining type can exhibit ei-

ther similar chemical resistance properties or

remarkably different chemical resistance properties.

It cannot be overemphasized that applying

polyurea linings over damp surfaces or placing the

lining in service prematurely can lead to significant

loss of adhesion and early failure of the system.

Because of the fast reactivity of the isocyanate-amine reaction, special spray application

equipment may be required that uses impingement mixing, i.e., the base and hardener compo-

nents are mixed externally at the tip of the spray gun. Not surprisingly, this type of application

invariably requires

• a fairly precise matching of base and hardener viscosities;

• heating the components; and

• ensuring the correct pressure at the tip. Otherwise, mixing is incomplete, and the chemical

and physical properties of the polymer are compromised.16

The rapid curing characteristics of polyureas can lead to substrate adhesion difficulties be-

cause of the limited time that is available for the films to wet the substrate. (Wetting provides

an intimate degree of contact between the rapidly gelling resin and the substrate.) The limited

wetting time can cause difficulties when applying polyureas over concrete, especially if it has

been abrasive blasted to remove the cohesively weak, cement-rich outer layer that has devel-

oped against the formwork. In areas where the polyurea needs to be terminated, some manu-

facturers require a set of sawcuts (often two) into the concrete parallel to the intended edge to

form a termination notch. These notches are typically about 5–6 mm wide by about 10 mm

deep and provide an additional physical anchor.

In addition, the fast reactivity makes touch-up and repair by brush application difficult on

small areas. Polyurea coatings must be spray-applied; therefore, tying-in to an existing

11

Polyurea lining in wastewater treatmentclarifier26 (concrete substrate)

Rapid productivity in shop and field applications

Not sensitive to moisture

Fast setting and faster cure than polyurethanes, e.g., in seconds

Superior to polyurethanes with respect to application under high humidity

Customized water and chemical resistance, flexibility, and impact resistance

Low surface friction—excellent hydraulic characteristics for pipeline internals

Low VOC—compliant with stringent air pollution regulations (VOCs)

Can be applied at sub-zero temperatures

Good elongation/flexibility

High thermal stability under dry conditions

Advantages of Polyurea Linings

Disadvantages of Polyurea Linings

Poorer wetting out of substrates, due partly to very rapid set times

Potential allergic reactions due to any freeisocyanate content

Susceptible to undercutting and peeling when immersed linings are mechanically damaged if not formulated properly for this service

Can be difficult to touch up and repair

Poor hot water adhesion

Relatively low alkali and solvent resistance

Poor color retention in aromatic polyureas subject to UV exposur

Limited raw material options compared topolyurethanes and polyurethane hybrids

Very fast cure properties reduce recoat windows, thereby increasing the risk of layering


coating is difficult. Some manufacturers make

special repair grades, but these are often

heavily modified with diluent resins to achieve

sufficient pot life and viscosity for brush appli-

cation. Unfortunately, the modifications can

drastically alter the repair-film properties, in-

cluding loss of mechanical and chemical resist-

ance.

With a relatively large number of isocyanate

and amine components to choose from, the

polyurea chemist can formulate elastomer

films with various cure speeds and with good

flexibility, elongation, and tensile strength prop-

erties. Depending on the amine backbone, the

films can be formulated with good water resist-

ance properties for immersion service in the

wastewater industry. However, the hydrocar-

bon solvent resistance of polyurea linings (es-

pecially to aromatic solvents) is typically poor.

One of the very common challenges with

polyureas is their very short recoat windows due

to fast cure times. It is common for polyureas to

demonstrate layering and poor bonding between

coats because of the fast cure times.

As far as temperature resistance is con-

cerned, while the dry temperature resistance

of polyurea linings can be up to 150 C, even

the most thermally stable polyurea linings will

probably not survive hot aqueous immersion

environments above 50 C. For oilfield serv-

ices, pure polyurea products may have limited

use due to their poor resistance to polar sol-

vents.

Some of the advantages and disadvantages of

polyurea linings are summarized in the chart on

p. 51.

Hybrids: Film FormationCustomized hybrid linings can be beneficial for owners and applicators. For instance, hybrid linings

can be formulated to exhibit significantly harder and better damage resistance than a typical

polyurea, while also retaining a linear and somewhat flexible polymeric structure. By virtue of their

outstanding barrier properties and elongation features, hybrid linings are well suited to protect the

internals of concrete digesters.

Hybrid polyurethane/polyurea linings can be formulated to have the best combination of proper-

ties of the two technologies.8 The hydrophobic character of some of the aromatic polyurethane-

polyurea hybrids is very similar to that of high-performance, immersion-grade epoxies. Hence, the

moisture vapor transmission of the hybrids is often below a measurable quantity when tested as per

12

Rapid productivity in shop and field applications

Fast cure and fast return to immersion service within minutes of application

Wider range for reaction time and performance properties

Caustic resistance: 50% at 65 C—superior to polyurethane linings

Customized water and chemical resistance, flexibility and impact resistance

Generally, good cathodic disbondment resistance at temperatures below 50 C

Films are resistant to abrasion, erosion, and impact

Films that are unaffected by normal shrinkage cracks in concrete

Low surface friction that enhance hydraulic characteristics for pipeline internals

Repairable by hand within minutes (kits available).

Advantages of Hybrid Linings

Susceptible to undercutting and peeling when immersed linings are mechanicallydamaged if not formulated properly for this service

Potential allergic reactions due to any free isocyanate content

Poor color retention with UV exposure in hybrids derived from aromatic isocyanates

Disadvantages of Hybrid Linings

Polyurethane hybrid lining on steel internals of penstock8


ASTM E96, Method B.

Hybrid linings have the ability to incorporate geotextile fabric, fiberglass reinforcement, woven

polypropylene, and polyester fabrics to produce a composite with improved properties. These in-

clude tear strength; crack-bridging capability; and the ability to cope with surface moisture and out-

gassing during application, and subsequent movement in a substrate such as concrete.

The longer wet time of the hybrid facilitates penetration into both the substrate and any internal

reinforcement being used, thereby improving wetting and offering superior mechanical adhesion.

With ultra fast-set coatings and linings such as polyureas, this type of mechanical adhesion is ex-

tremely difficult to achieve. On damp surfaces, the hybrid will still adhere to the substrate. Some

pin-holing can occur in the “glue-coat” due to outgassing. Outgassing will not affect the topcoat be-

cause the outgassing will dissipate in the geotextile. On the other hand, when a polyurea lining is

applied to a damp surface, it will cure very fast, so it is less likely to outgas. However, the polyurea

lining also will not adhere to the substrate.

Ultra-high-build aromatic polyurethane hybrids have been shown to possess exceptional resist-

ance to water and wastewater immersion services. Their tough, robust, and flexible films are similar

to some of the best high-tensile strength polyurethane films and have been used for more than 20

years in demanding immersion exposures where abrasion and impact are additional factors of con-

cern. Repair kits of hybrid linings are available for touch-up joints and connections.

Like polyurethane and polyurea linings, hybrids also have extremely fast return-to-service times

13

Case History: Penstock Internals, AustraliaSince the early 1990s, some polyurethane hybrids have been used to internally line penstocks inNorth America.28 The rapid productivity associated with the use of these linings and their solvent-free safety advantages made them particularly attractive for large scale penstock projects. Theseone-coat polyurethane hybrids have had great success protecting thousands of rivet heads in im-mersed conditions in penstocks.Based on this success, in 2004, the internals of a penstock at a power station in Australia were

lined with a one-coat system of a solvent-free elastomeric polyurethane hybrid. Several hundredmeters of three- and four-foot internal diameter pipe were lined.First, the carbon steel internals were abrasive blasted to SSPC-SP 10, Near White Metal, using

a robot (a self-propelled, automatic blasting unit). Second, the polyurethane hybrid lining was ap-plied at approximately 40–60 mils DFT, as shown in photo at left.After eight years, the penstock has shown no evidence of any lining problems.

Polyurethane hybrid lining8 in a pen-stock (steel substrate; robotic, self-propelled automatic blasting unit)

Case History: Wastewater Treatment Clarifier, U.S.The eight year old concrete walls and floor of a primary clarifier in a food processing plant hadsustained considerable damage by erosion and chemical attack from a solution of calcium sul-phate. The owner was concerned that the concrete was in imminent danger of failure.Given that an epoxy lining system had been used in the past and had failed in three years,

the owner elected to re-line and protect the 22,000 sq ft of damaged concrete with a propri-etary polyurea lining system.All concrete surfaces were abrasive blast cleaned, followed by a spray application of a spe-

cialty concrete primer.27

A spray applied topcoat of .080 inches polyurea was then applied. The project was completed in 24 hours and re-watered in two hours (See photo at left and onp. 50).

Polyurea lining in wastewater treat-ment clarifier26 (concrete substrate)


for ambient temperature water and wastewater

immersion service (domestic waste and indus-

trial waste at a pH from less than 1 to 14).

Certain hybrid linings use hydroxyl- and

amine-containing resins that have very little to

no oxygen atoms, or other atoms that would in-

crease polarity in the resin backbones. This

chemical make up causes the hybrids to be

much more hydrophobic than polyurethane

and polyurea linings. The hybrids also resist

chemicals as much as, or better than, many

polyurethane and polyurea linings.

General Discussion Table 2 provides a general comparison of

polyurethane, polyurea, and

polyurethane/polyurea hybrid properties in the

coatings and linings industries.

A high degree of surface preparation must

be done in order to ensure that the solvent-

free and high-build polyurethane, polyurea,

and hybrid linings will perform well for many

years and provide the owner with a good re-

turn on his investment. For optimum results,

steel surfaces should be free of surface con-

taminants such as soluble salts, grease, and oil; be abrasive blasted to a minimum SSPC-SP 10;

and have a deep and jagged profile of 3–5 mils (75–125 microns).

By virtue of their short pot lives and fast curing properties, these linings are applied using plural-

component, hot airless spray equipment. Humidity control is important, and the surface temperature

should be at least 3 degrees C above the dew point.

One of the key areas where polyurethane and hybrid technology have demonstrated long-term

immersion performance has been in the lining of potable water tanks and pipes. Certified to the

ANSI/NSF 61 standard, these coatings have a long track record when applied to steel substrates.

The same is true for polyurethane coatings applied to the interior and exterior of steel per AWWA

C222-99. The rapid curing characteristics of this technology, coupled with the need to use special-

ized equipment, behooves owners to select qualified applicators and ensure that third-party inde-

pendent inspection is provided to ensure a successful application.

Lining and relining steel penstocks is another application where polyurethane and hybrid

polyurethanes excel.14,17 Of particular note is that a single-coat application of these films can provide

long-term corrosion protection to rivets in penstocks, some designed and installed in the 1940s.

Another immersion environment where polyurethane and hybrid polyurethane linings have been

used is the underwater hulls of ice breakers.18 The excellent abrasion resistance and low frictional

resistance indicate that these coatings would be well suited to resist abrasion and ice impact. While

these characteristics proved to be the case on many icebreakers, in more recent years, epoxy lin-

ings have become favored more than polyurethane and hybrid polyurethane linings for icebreaker

underwater hulls.

14

Property Polyurethane Polyurethane Polyurea Polyurethane HybridHybrid Advantage

Gel time Seconds Instant set Instant set Superiorto hours to minutes substrate wetting

Tack free Minutes One minute 6–30 Rapid returnto hours to hours seconds to service

Tensile Up to Up to Up to Higher tensilestrength 7,000 psi 7,000 psi 4,000 psi strength

Tensile Up to 500% Up to 500% Up to 700% Lower elongationselongation however, significantly

lower permeability

Shore 50A to 85D 5OA to 85D 50A TO 85D Harder, betterhardness “D” impact resistance

Abrasion Pure As low as 76 mg loss Hybrids oftenresistance polyurethanes 30 mg (H18 wheel) have better

typically (H18 wheel) abrasion resistancehave best AR props

Tear resistance Up to 500 pli Up to 500 pli Up to 500 pli Similar tearresistance

Moisture vapor Too low Too low 42 Significantly bettertransmission to detect to detect g/m2/24hrs resistance to

the passageof moisture

Table 2: General Comparison of Polyurethane, Polyurea, and Hybrid Properties in the Coatings and Linings Industry


The low temperature cure of some

polyurethanes and hybrid urethanes is very

useful in cold climates. In the Canadian oil

patch, for instance, where several fast-set

epoxy coatings are used for transmission

pipeline externals, some owners prefer the

use of fast-set polyurethane linings. Judi-

ciously selected and qualified high-perfor-

mance polyurethanes and hybrids are well

suited to year-round rehabilitation of steel

pipelines.19 It should be noted, however, that

the service temperature for suitable

polyurethanes is invariably rated up to 65°C,

i.e., less than the temperature of alternative

qualified epoxy coatings with high glass tran-

sition temperatures.

Considering accelerated laboratory testing,

the authors have stressed, in previous work,

the importance of not relying heavily on cer-

tain tests and understanding the relevance of

said tests.20 For transmission pipeline coat-

ings, caution must be exercised in not placing

too much credence in any individual pre-quali-

fication test. Therefore, testing programs for

epoxies, polyurethanes, and polyurethane hy-

brids typically consist of a regime that in-

cludes electrochemical impedance, cathodic disbondment resistance, wet adhesion, impact

resistance, flexibility, hardness, and gouge-resistance assessments.

Table 3 shows the pre-qualification test results for a thick film, solvent-free polyurethane hybrid

developed for use on a major oil company’s transmission pipelines.21 The coating’s wet adhesion

characteristics and its impact resistance were excellent, and it displayed good flexibility at the 1.5

degrees per pipe diameter bend, but displayed poor flexibility at a 2.5 degree bend. Gouge resist-

ance was rated at 54.1% (average gouge depth of total film thickness). The coating showed excel-

lent electrochemical impedance characteristics, with the log Z impedance remaining constant

during 28 days of exposure to the test conditions.

In the final analysis, all the test results were excellent, except for one anomalous result in the CD

test in accordance with CSA Z254-20-02. Outstanding cathodic disbondment resistance was exhib-

ited by the polyurethane lining at elevated temperatures. At 80C for 28 days, the average disbond-

ment radius was 0.6 mm; at 65C for 28 days, the average disbondment radius was 1.8 mm.

However, at 23C for 28 days, the average disbondment radius was 35.9 mm. At first glance, this re-

sult would disqualify the coating until the coating chemistry and the relevance of the test methodol-

ogy were considered in addition to other physical tests. The coating has a much higher tensile

strength (6,000 psi) and elasticity at ambient temperature when compared to its tensile adhesion

(3,500 psi). Therefore, in the CD test at 23 C, this polyurethane coating had a very high molecular

strength, but the coating would peel when pried off in the CSA test, thereby erroneously giving the

impression of poor adhesion. Elevating the test temperature to 65 C and 80 C progressively lowers

the tensile strength, and the coating subsequently becomes more difficult to pry from the substrate.

Hence, caution should be exercised in the disqualification criteria for a polyurethane (or polyurea

15

Table 3: Transmission Pipeline Coating Testing

Solvent-Free Hybrid Polyurethane: Testing in Accordance with Qualification Protocol for Liq-uid Epoxy Coatings

Test Test Method Test Results28 day cathodic disbondment @ 20C 35.9 mm28 day cathodic disbondment @ 65C CSA Z245.20-06 1.8 mm28 day cathodic disbondment @ 80C Clause 12.8 0.6 mm

28 day adhesion @ 65C CSA Z245.20-06 #2 ratings28 day adhesion @ 80C Clause 12.14 #1 ratings

1.5 J impact resistance @ -30C, -10C, 0C, CSA Z245.20-06 No holidays23C, 65C and 75C Clause 12.121.5° flexibility @ 0C No cracks or

1.5° flexibility @ -30C CSA Z245.20-06 stretch marks

2.5° flexibility @ 0C Clause 12.11

2.5° flexibility @ 0C

Hardness (-30C, -10C, 0C and 23C) Shore D 80 to 85

ASTM D2240Hardness (65C and 80C) Shore D 57 to 68

Gouge Test NACE Draft 54.1%

Electrochemical Impedance Spectroscopy ISO 16773 Log Z > 10(10.7 to 10.8)

Cracking and

disbondment


and polyurethane hybrid) coating based on ra-

dial disbondment measurements obtained

from CD tests.

The immersion performance of the solvent-

free polyurethane, polyurea, and polyurethane

hybrid linings is a function of their chemistries

and the nature of their dry and wet adhesion

at the polymer-substrate interface. Micro im-

purities (e.g., micronic backside contamina-

tion) embedded in surface irregularities and

adsorbed layers of gaseous or liquid phase

molecules are more likely to be problematic

for the application of extremely fast-set and

rapidly curing linings that have little time to

wet out the surface.

In earlier work, the authors examined the in-

fluence of surface profile characteristics of

steel on coating and lining performance in im-

mersion. Failure to understand how the wet-

ting properties of the lining as well as the

adhesion forces can lead to serious repercussions for lining performance.22 In the case of 100%-

solids coatings that require heat for molecular mobility in order to facilitate mechanical and polar

adhesion, it is important to have a clean and well roughened substrate with a large number of reac-

tive sites.

The adhesion of organic coatings applied to steel surfaces is often described in terms of interfa-

cial hydrogen bonding between polar molecules, such as -OH and -COOH groups.2 It is reasonable

to postulate that the viscous polyurethane, polyurea, and hybrid linings cure so fast that they have

little time to (a) fully wet the steel surface or (b) develop the maximum number of hydrogen bonds

with the iron oxide-OH groups on the steel. Adhesion viewed in terms of Lewis acid-Lewis base the-

ory throws extra light on what is happening at the polymer-substrate interface.23,24 This theory is es-

pecially helpful regarding the wet adhesion characteristics of these linings when subjected to water

immersion. Acid-base theory envisages adhesion between acidic groups on abrasive-blasted steel

interacting with basic groups on the polymer. In essence, the greater the interaction is, the better

the adhesive bond will be. For instance, the basic groups on polyurethanes, polyureas, and their

hybrids are weak Lewis bases, and they form bonds with the iron oxide on carbon steel. These

weak bonds can readily be cleaved by water molecules when the coating is mechanically damaged

in immersion.

Hence, the real world observation is that several polyurethanes, polyureas, and hybrids may peel

to some extent away from carbon steel when damaged in immersed conditions. The authors are

currently investigating these adhesion phenomena on steel substrates in more detail.

In the protection of new and old concrete, many polyurethane and polyurethane hybrid linings

have demonstrated excellent service in a variety of municipal wastewater applications because

they can protect against microbiologically induced corrosion (MIC). Some polyurethane linings have

even been formulated with special anti-bacterial additives that are said to increase resistance

against MIC.25

Specialty polyurea linings can also provide very good protection to concrete in corrosive environ-

ments. For instance, spray applications of polyureas have been carried out inside neutralization

ponds in cogeneration facilities. Often, an epoxy primer is used to aid adhesion to the concrete fol-

16

Fig. 8: Bonded geomembrane (polyurethane hybrid) to a concrete wall

Bonded Geomembrane Lining

POLYURETHANE HYBRID BASECOAT

POLYURETHANE HYBRID TOPCOAT Outgassing(air & water vapor)

HydrostaticInfiltration

Concrete

GEOTEXTILE FABRIC

EPOXY PRIMER (Optional)


lowed by one coat of polyurea.26 The asset can be rapidly returned to service because of the rapid

curing characteristics of the polyurea.

An innovative “bonded geomembrane” system for the application of certain polyurethane hybrids

to concrete surfaces has gained acceptance and is schematically depicted in Fig. 8. The geomem-

brane basically consists of pre-cut, heat-set, non-woven 100% polypropylene geotextile fabric pan-

els that are embedded between two layers of polyurethane hybrid.8 The panels are pressed onto a

still-fluid basecoat (or the concrete) and are held in place with Hilti-studs. Then, the panels are top-

coated. The system is especially suited to vertical, new, or old poured-in-place concrete surfaces

(walls). The polyurethane hybrid is reported to bridge bugholes and other voids in concrete as well

as eliminate pinholes produced by the normal outgassing of concrete. Hence, the fabric filters and

dissipates air or water vapor throughout itself. Therefore, there is said to be no way for outgassed

air to blow holes through the coating when it is being applied as a topcoat onto the geotextile fabric.

Once applied, (a) the embedded fabric can dissipate hydrostatic pressure and (b) remain unaf-

fected by normal surface shrinkage cracks, most dynamic cracks and the designed movement of

expansion joints in concrete.

ConclusionsSolvent-free polyurethanes, polyureas, and polyurethane/polyurea hybrid technologies have shown

promise for immersion service in various market segments.

A wide array of solvent-free technologies of this type can be formulated to have a plethora of

chemical physical properties by carefully selecting the amines, polyols, or a combination thereof.

This is particularly true for the polyurethanes and polyurethane hybrids.

Solvent-free polyurethanes, polyureas, and polyurethane/polyurea hybrid technologies can be

used in either a pure form or when slightly modified to customize required performance properties.

AcknowledgementsThe authors are indebted to Dan Schneider of Polibrid, Jeff and Mark Buratto of Lifelast Inc., and

Mark Dromgool of KTA-Tator Australia for their valuable insight with respect to polyurethane,

polyurea, and polyurethane hybrid linings.

References1. H. Hower, “Polyureas—What’s in a Name”? JPCL (December 2003), pp. 31–33.

2. C.H. Hare, Polyurethanes. In Protective Coatings, Fundamentals of Chemistry and Composition,

1994.

3. T. Kenworthy, “100% Solids Polyurethane and Polyurea: A Comparison of Properties and Uses,”

JPCL (May 2003), pp. 58–63.

4. R. Alliston and J. Dzatko, “Recent Advances in Epoxy Coatings for Automated External

Rehabilitation of Pipelines,” NACE Northern Area Western Region Conference, Anchorage, AK,

2001.

5. D.J. Primeaux II, “Polyurea Elastomer Technology: History, Chemistry and Basic Formulating

Techniques,” 2004.

6. D.J. Primeaux II, Two Component Polyurea Coatings/Linings. In Selecting Coatings for Industrial

and Marine Structures, SSPC: The Society for Protective Coatings, Pittsburgh, PA, 2008,

pp. 107–123.

7. D.J. Primeaux II, “The Protective Coatings Specialist and Polyurea: The Sequence of Events,” JPCL

(September 2012), pp. 50–57.

8. D. Schneider, Polibrid Coatings Inc., personal communication, August 2012.

9. M. Winter, “Discussion on Polyurea Linings for Oilfield Applications,” International Paint LLC, April

17


2011.

10. “Introduction to Thick-Film Polyurethanes, Polyureas and Blends,” T-6A-67 Technical Committee

Report No. 6A198, NACE International, Houston, TX, 1998, pp. 1–8.

11. M. Broekaert, “Polyurea Spray Coatings: The Technology and Latest Developments,” European

Coatings Conference, pp. 37–55.

12. “Polyurea Elastomeric Coating/Lining Systems,” Polyurea Development Association General

Guidelines, Kansas City, MO, 2003.

13. G. Oertel, Polyurethane Handbook, Second Edition, Hanser Publishers, 1994.

14. M. Buratto, Lifelast Inc., personal communication, August 2012.

15. S. Guan, “High Solids and 100 Percent Solids Aliphatic Polyurethanes for Exterior Applications: A

Survey of Approaches,” JPCL (July 1997), pp. 44–52.

16. D.J. Primeaux II, “Spray Application of 100% Solids Plural-Component Aliphatic Polyurea

Elastomer Systems,” JPCL (March 2001), pp. 26–32.

17. R.D. Stutsman, “Innovations in Penstock Lining,” Hydro Review, May 1993.

18. “Study on Hull Corrosion and Coatings,” B.H. Levelton & Associates Ltd., October 1988.

19. R. Garret, HDIM, personal communication, November 2012.

20. M. O’Donoghue, V.J. Datta, M. Winter, and C. Reed, “Hubble, Bubble, Tests, and Trouble: The

Dark Side of Misreading the Relevance of Coating Testing,” JPCL (May 2010), pp. 30–45.

21. J. Buratto, Lifelast Inc., personal communication, October 2012.

22. M. O’Donoghue, V.J.Datta , and R. Spotten, “Angels and Demons in the Realm of Protective

Coatings: The Underworld of VOCs,” JPCL (April 2011), pp. 14–29.

23. F.M. Fowkes, “The Role of Adhesion in Corrosion Protection by Organic Coatings,” JOCCA

(October 1985), p. 229.

24. C. Reed, International Paint LLC, personal communication, October 2012. 25.

25. Madison Chemical, http://www.madisonchemical.com.

26. J. Wynne Darden, D. Zabinski, and S. Smith, “Spray Polyurea Coatings for Protecting Concrete

Structures,” pp. 178–184.

27. L. Hanson, Hanson Group, personal communication, November 2012.

28. K. Nollsch, International Paint LLC, personal communication, November 2012. JPCL

18

JPCL

Vijay Datta, MS, is the Di-

rector of Industrial Mainte-

nance for International

Paint LLC, USA. He has

more than 40 years of ex-

perience in the marine and

protective coatings industry.

Mike O’Donoghue, Ph.D.,

is the Director of Engi-

neering and Technical

Services for International

Paint LLC, Canada. He

has more than 30 years of

experience in the protec-

tive coatings industry.


Paint & Coatings–Where Are We Now?

Paint & Coatings 19

By Brian GoldieJPCL

s with other topics in this special section, coatings developments have been covered in

JPCL regularly since 1985. The last main review was in the 25th Anniversary issue (Au-

gust 2009), where Michael Donkin summed up the changes in coating formulation for the

heavy-duty protective market since JPCL started. He discussed the drivers for change over that time

and how they had led to the introduction of new technologies. The present article will summarize

Donkin’s findings and then look at key developments for the protective and marine coatings since

2009. This article is not claimed to be comprehensive, but is instead a guide to some of the main con-

tinuing trends and innovations.

The 25-Year ReviewDonkin’s August 2009 article discussed changes in coatings formulation over 25 years and the key

drivers for change. Drivers included increasing levels of legislation relating to protection of the environ-

ment from air pollution by reducing the emissions of volatile organic compounds (VOCs) from coatings,

and the need to reduce the use of raw materials that can pose risks to worker health and safety and to

the environment. In addition, there were higher customer expectations of performance and the need to

increase the lifetime of assets while reducing life cycle costs.

In the 1980s, there were very few VOC regulations for coatings, but by the 1990s, a revision of the

U.S. Clean Air Act resulted in national VOC rules, which have been getting stricter. There are also re-

gional, state, and local VOC regulations in the U.S. In Europe, the EU solvent emissions directive was

issued in 1999, but it wasn’t until 2005 that the first restrictions on release of VOCs started to apply.

These regulations meant the virtual end of thermoplastic coatings (vinyls and chlorinated rubbers) be-

cause their very high VOC levels would never meet the regulations. Two-pack materials such as epox-

ies and polyurethanes became the resins of choice, but it was (and still is) a challenge for formulators

to maintain the high performance obtainable with these systems while reducing the level of solvent

A

© istockphoto.com/mstroz


used and the resultant VOC emissions. Increas-

ing the volume solids of the coating would re-

duce the VOC content, but this is not easy to do

without affecting application, drying, and other

properties of the coating, particularly if very high

solids levels are needed. Alternative resins and

curing agents are needed to achieve these very

high solids and/or more sophisticated application

equipment to apply them due to high viscosities.

An alternative technology was waterborne coat-

ings, which could be formulated with very low

VOC levels. Going back 25 years, waterborne

technology was limited to single-pack emulsions,

principally for interior use and typically not suit-

able for heavy-duty because of slow drying, poor

film properties, and adhesion when applied in

the field. Donkin did point out that over 25 years, two-component waterborne systems, such as epoxies

and polyurethanes, have been developed with performances close to their solvent-borne counterparts .

Raw materials identified as harmful to operators and the environment in the 25-year review included

lead and hexavalent chromate pigments, coal tars, and some plasticizers for acrylic emulsions. Cur-

rently, lead anticorrosion pigments are not used; chromate anticorrosion pigments have very limited

use (mainly in etch primers) in the protective coatings area; and the use of APEO plasticizers (alkyl

phenolethoxylate) is very restricted. There were periodic concerns about health risks from iso-

cyanates in coatings, but, in general, the industry knows how to handle these risks safely. In Eu-

rope, the REACH regulations began causing an area of uncertainty among formulators about what

materials may disappear from the market because of toxicity, or, more probably, the cost effective-

ness of screening these materials, which are often produced (and used) in small quantities.

Key Changes Since 2009The drivers for development identified in the August JPCL’s 25-year review are still valid, so what major

coating developments have occurred since then?

High-Solids vs Waterborne Coatings

So far, there has not been a dominant technology to meet the current environmental regulations. A

good barometer of coating development is to look at the (new) raw materials being promoted at trade

shows. The European Coatings Show is the largest and most important exhibition for the paint industry.

At the 2011 event, the main trends were an increased emphasis on waterborne systems, rather than

high solids, as a means of meeting the VOC requirements, and more attention to smart, or functional,

coatings.

However, this trend has not yet transferred to the protective or marine maintenance coating markets,

where use of waterborne coatings is relatively low, still due mainly to film forming and drying problems

in the field, as well as higher costs compared to traditional solvent-borne coatings. As a means of re-

ducing VOCs, higher solids and solvent-free coatings have been making more inroads. This is due es-

sentially to developments in curing agent technology giving faster cure times, and, to a certain extent,

to improved application equipment with better control on component mixing ratios of these two-pack

systems.

20

© istockphoto.com/dbvirago


Waterborne Coatings

The introduction of waterborne coatings has

been limited essentially to two market areas:

coatings for internal use or very low and now

moderate corrosivity areas, and sealants and

coatings for concrete.

As metal coatings, low-VOC, two-component

waterborne polyurethanes have been developed

as primers and direct-to-metal systems for com-

ponents for light industrial projects. For concrete

and masonry applications, acrylic systems are

popular as topcoat/sealers to give good weather

and chemical resistance.

Waterborne epoxies have also been devel-

oped as concrete coatings, particularly for coat-

ing moisture-sensitive concrete (flooring).

Systems have been developed as sealers and primers that can also be applied over green concrete

and that have good adhesion without the need for a profile. Waterborne epoxy floor topcoats are also

available, including antistatic versions.

High-Solids Coatings

Conventional solvent-borne coatings have volume solids contents of around 50–60%. High-solids

coatings can be divided into solvent-free systems (100% solids) and those solvent-borne systems

with higher solids than the traditional coatings. In this summary, high-solids coatings are defined as

those with volume solids greater than 70%.

100% Solids Coatings

Developments in solvent-free systems include pure aliphatic polyurea topcoats for increased UV pro-

tection and good gloss and color retention, and flexible polyurethane systems with good waterproofing

properties for concrete floors, particularly in multi-story car parks exposed to aggressive environmental

conditions.

However, the most common 100% solids systems have been based on epoxy technology. Good ad-

hesion to steel and concrete, together with improved chemical and abrasion resistance compared to

the traditional solids content coatings, can be achieved with these systems.

Higher-Solids Coatings

The higher-solids protective coatings are generally based on polysiloxane resins and polyureas. High-

gloss topcoats for steel, with good durability and corrosion protection as well as fast cure have been

developed based on modified polysiloxanes. An even more environmentally friendly type of system, an

isocyanate-free single-component acrylic-siloxane, features good abrasion and a low VOC.

Aliphatic polyurea and polyaspartic resin systems also feature fast cure and high gloss for concrete

floors and for medium corrosivity steelwork protection.

High-solids epoxies with a range of curing agents, including phenalkamines, are used for immersion

and atmospheric protection of steelwork and concrete floors.

Conventional Coatings

Although the trend is for higher-solids (or waterborne) coatings to meet the VOC regulations,

there have also been developments in the traditional solvent-borne coatings, although volume

21

© istockphoto.com/leofrancini


solids have increased to nearer the 60-70%

level. Again, urethanes and epoxies dominate

the developments, with acrylic urethane fin-

ishes giving high durability protection to the

structural steel of bridges, storage tanks, and

other structures, and polyurethanes providing

heavy-duty concrete floor coatings. The ag-

gressive demands of the offshore industry are

being met with high-performance zinc-rich

epoxy and conventionally pigmented epoxy

primers.

Specialty Coatings

Intumescent Coatings

Fire protection has become an important subject for many raw material suppliers, as observed at the

European coatings shows in 2011 and 2013, and for paint companies. For cellulosic fires, 120 minutes

of protection are being provided by one-component, solvent-borne, acrylic intumescent coatings, with

some systems that can be applied under shop conditions or onsite.

Marine Coatings

As with protective coatings, there have been changes in marine coating over the past 30 years. The

25-year review identified the key developments that had occurred up until 2009. These mainly in-

volved hull coatings, resulting in two alternative high-performance antifouling technologies: tin-free

polishing coatings (copper-containing), and low-energy, foul-release coatings (silicon and fluo-

ropolymers).

Since 2009, very little has occurred, but various paint manufacturers have been making incre-

mental changes to their products to establish differentiation among them and have been partnering

with third-parties in an attempt to develop a methodology for measuring and validating claims about

potential fuel savings.

However, a copper-free, high-performance antifouling has become available that is based on self-

polishing binder technology and is aimed specially at keeping underwater hulls clean from fouling

while vessels are stationary in seawater.

The other major concern in the shipbuilding industry has been the corrosion of seawater ballast

tanks and the establishment of the IMO’s Performance Standard for Ballast tank coatings. The IMO

requirements were essentially “copied” for a regulation describing a performance standard for cargo

oil tanks. This regulation has provoked some concern about the testing of (new) coatings to meet

the standard.

Polysiloxanes, which are showing increased usage in the protective coatings sector, are also

starting to appear in marine coatings, with durable, aesthetic topcoats that are easy to clean and

maintain, thus saving on costs

The FutureWhat does the future hold for protective and marine coatings? Health & safety and environmental

regulations will still drive coatings development. It is most likely that the VOC restrictions will get

even more restrictive. We do not know what technologies will become more dominant: waterborne

or high-solids. Various industry forecasts predict strong growth in waterborne systems, and going

by the products exhibited this year at the European Coatings show, the resin suppliers are all active

in this area. However, when I talk to the formulating chemists in the protective coating manufactur-

22

© istockphoto.com/GBlakeley


ers, they all agree that for the next 10 to 20 years, 80% of the heavy-duty and marine coatings will

be solvent-borne, albeit with higher volume solids than currently.

The use of other toxic or hazardous raw materials will be banned and more environmentally sus-

tainable raw materials will become available.

With a great deal of research being carried out in nanotechnology for coatings, it is expected that

we will see new “smart” or functional coatings coming to the market. Already, we have had demon-

strations of what this technology can deliver, and market acceptance should follow once new formu-

lations have been demonstrated in the field and production methods have been scaled-up.

Brian Goldie, technical editor for JPCL, has worked with protective coatings for many years,

including in the oil industry.

23

JPCL


Improving Polyurethane Pipe Coatings for Harsh Conditions

PolyurethanePipe Coatings 24

By Andreas aus derWieschen, MatthiasWintermantel, ToddWilliams and AhrenOlson Bayer MaterialScience AG

iquid polyurethane (PU) coating systems are of growing importance in the field of external

coatings for oil and gas pipelines. Coating systems based on aromatic polyisocyanates

and pre-polymers are used for new pipeline construction and for maintenance work.

Major drivers for the use of polyurethane coatings in pipe applications are their favorable cure char-

acteristics combined with superior mechanical properties especially under harsh conditions. Solvent-

free, two-component polyurethane systems have been approved as suitable protective coatings

systems within the pipeline industry and have been used for new tubes (steel and ductile iron) and for

field joints.

Furthermore polyurethanes are of growing importance for the renovation of oil and gas pipelines in

the field due to their ability to cure at low temperatures and their exceptional mechanical properties.

L

©iStockphoto/olegusk © 2011-2015 Technology Publishing Co.

Application PropertiesSolvent-free two-component PU coatings have

the ability to create an inherent thickener effect

during application. This effect avoids sagging on

vertical surfaces and allows the formation of high

film thicknesses applied in one coating layer.

Therefore PU systems can fulfill the postulated

requirements with dry film thicknesses of about a

minimum of 500 µm up to 5,000 µm and higher.

Curing Time and ReactivityStandard polyurethane systems are touch-dry

after approximately 60 minutes at 20 C or ap-

proximately 100 minutes at 5 C. The time for

through drying can vary from approximately 50

minutes to approximately four hours at 20 C.

The reactivity of a polyurethane system can be

controlled by incorporating suitable catalysts.

Figure 1 shows the potential versatility of PU

coatings, adjusting reactivity by means of four

different formulations. With formulation Nos. 2

and 3, approximately 90 percent of the end

hardness – depicted as Shore D – has been

reached after roughly four hours which makes

these coatings generally suitable for field appli-

cation. Furthermore two formulations (Nos. 1

and 4) provide Shore hardness of D50 and D60

after only five minutes which would make those

combinations generally suitable for plant appli-

cation.

Mechanical PropertiesMost relevant technical parameters for oil and

gas pipeline coatings are related to mechanical

properties such as film hardness and flexibility along with adhesion, and resistance to chemicals

and solvents. Liquid polyurethane pipe coatings typically provide increased impact resistance at

higher Shore hardness than standard pipe-coating epoxy systems. High-impact resistance is bene-

ficial because the transport of coated pipes to the site and the laying procedure in the soil can dam-

age the coating. Flexibility is important because PU-coated tubes in the field must endure bending

and must withstand frost during winter in colder regions. High abrasion resistance of the coating is

advantageous for withstanding soil stress.

The physical strength of polyurethane systems allows them to withstand mechanical forces longer,

such as creep. These mechanical properties can be customized by varying the ratio of hard and soft

segments, molecular weight and the crosslinking density of the cured film. Therefore it is possible to

create different PU coatings with physical properties that can range from soft, plastic across elastic up

to hard, rigid and even brittle.

Figure 2 displays the potential versatility in adjustment of mechanical properties of polyurethane

coatings. It compares different polyurethane formulations in terms of flexibility – measured as elonga-

25

Fig. 1: Polyurethane pipe coating formulations can be adjusted for shop-applied or field-applied applications. All images courtesy of the authors unless otherwise noted.

Fig. 2: High versatility for adjusting mechanical properties – elongation and Shore hardness


tion at break, and hardness – measured as Shore

D. It is possible to achieve different films by varying

elongation at break that ranges from roughly 5 per-

cent up to roughly 130 percent. The elongation at

break of standard polyurethane pipeline coatings

ranges in between 10 percent and 20 percent.

By combining polyurethane formulations which

provide different levels of hardness, it is possible to

create a coating system resembling a polyurea

system, with a hard primer plus an elastic layer; or

a three-layer system consisting of a hard primer

plus an adhesive plus an elastic polyethylene. As

shown in Figure 2, using PU1 (hard primer) as the

initial layer, PU4 as the intermediate coat and PU7

as the “elastic” finish coat, total film thickness of

1,000 µm, 3,000 µm, or even higher could be

achieved. The advantage of such a paint system is

its effective adhesion due to all components being

of the same technology, PU onto PU.

Development of Rigid, Two-Component Polyurethane CoatingsMarket requirements led to development of rigid, two-component polyurethane coatings by improving

on already-established polyurethane raw materials. Desired attributes of this advanced coating in-

cluded serviceability for buried pipelines positioned above- and below-underground-water level, short-

drying time, short-curing time, single-coat suitability for direct-to-metal application, durability under

harsh conditions, favorable cathodic-disbonding properties, favorable impact properties and straight

mixing ratio.

Steps of development included screening of suitable building blocks; selection of the best candi-

dates for extended testing for anticorrosion properties, adhesion, porosity and curing characteristics;

working out start formulations for test coatings; working out straight mixing ratios and rheological pro-

file. The develpment outcome is a "rigid" or "strucutral" class of PU pipeline coatings based on new

polyols and polyisocyanate pre-polymers.

Laboratory TestingCathodic Disbonding Test

Various test procedures exist within the pipeline industry and have different requirements for voltage,

temperature, salt solution and test period. The most regularly-used test methods follow standards

ASTM G8, “Standard Test Methods for Cathodic Disbonding of Pipeline Coatings,” and ASTM G42,

“Standard Test Method for Cathodic Disbonding of Pipeline Coatings Subjected to Elevated Tempera-

tures.”

Polyurethane pipe coatings which provide higher crosslinking densities in the cured film usually pass

the cathodic disbonding tests up to 65 C. The prepared surface, specifically the roughness profile after

blasting, has an important influence on adhesion and cathodic-disbonding-test results. The minimum

surface quality should be Sa 2.5 with a roughness minimum of 50–70 µm, and a recommended rough-

ness of 80–100 µm.

Pipe coatings must fulfill certain cathodic-disbonding properties. Figure 3 illustrates a schematic de-

sign of a cathodic disbonding (CD) test. CD tests are used to evaluate the damaged coating's delami-

26

Fig. 3: Schematic design of the cathodic disbonding test


nation behavior using conditions that model the service environment including cathodic

protection, elevated service temperature, and salt solution (representing ground water).

Steel panels with different surface profiles (roughness) were tested at various tempera-

tures. Coated steel panels were sent to an independent test institute for investigation of

cathodic disbonding characteristics according to T/SP/CW/6 Part 1. The tests were car-

ried out for 15 days at 80 C and for 15 days at 95 C. The electrolyte was maintained at

30 C in both tests. The results of these tests were approximately 3 mm disbondment

after 15 days at 80 C and approximately 5 mm disbondment after 15 days at 95 C.

Figure 4 depicts the result of the cathodic disbonding test after 14 days at 80 C. The

result in terms of adhesion and disbondment is very good at surface roughness of ap-

proximately 30µm. The requirement is normally 80–120µm. In this case it was not possi-

ble to lift the coating with a knife at the end of the test.

Film Hardness and Impact Test

One development goal was to decrease the time involved in the en-

tire maintenance process, thereby reducing the time until backfilling

of the coated pipe could take place. The Shore hardness formation is

a good indicator of curing therefore measuring the hardness of the

applied film over time can provide an informative assessment of me-

chanical performance (Table 1).

After coated samples of a start formulation had been success-

fully tested, two field trials were carried out. The field application was

arranged in agreement with an oil and gas company in the Middle

East. It was done to study and evaluate the new building blocks for

rigid, two-component polyurethane coatings for external surfaces of

oil and gas pipelines under real conditions.

Blasting

After shot blasting the surface with garnet, the profile measured Sa 2.5 and the average

roughness was approximately 70 µm.

Application of the Test Coating

Two layers of the test coating were applied wet on wet with roughly 10 minutes of curing time

in between the coats. Each layer was applied with 3–4 passes (Fig. 5). The pot life measured

three minutes and after about 30 minutes the coating was tack free.

The final inspection after application on-site showed that leveling and sag resistance was

satisfactory. The dry-film thickness was measured with 1,650–1,900 microns. As no blisters

or failures were observed, backfilling of the pipe was done three hours after application.

Inspection of the Test Coating

After 15 months in wet soil with high salt content, the pipeline was excavated and the rigid

polyurethane test coating was inspected by experts from the participating oil and gas com-

pany. The coating was in excellent condition and did not show any damage, bubbles, rust or

delamination (Fig. 6, p 40). The oil and gas company representatives tried unsuccessfully to

cross-cut the coating by using a chisel.

27

Fig. 4: Rigid polyurethane coating after cathodic-dis-bonding test for 14 days at 80 C

Rigid Polyurethane Shore D Hardness @ RT

After 1h 73

After 3h 78

After 5h 78

After 7h 81

After 9h 81

After 24h 82

After 48h 82

After 7 days 82

Table 1: Measurement of Shore Hardness Over Time

Fig. 6: Inspection of rigid test coating after 15months. No defects or damages were observed.

Fig. 5: Application of test coating inthe Middle East


Comparison of Existing CoatingsThis positive result prompted a comparison with existing sol-

vent-free, aromatic, two-component polyurethane coatings

also deemed suitable for pipelines above- and below-ground

water level and specific service temperatures (Table 2).

Rigid Polyurethane Type 1

By roughly comparing four cases in consideration of the

crosslinking density of the cured film, the influence of the

crosslinking network on the coating properties was apparent.

The cured film of rigid polyurethane type 1 is highly

crosslinked yielding exceptional cathodic-disbonding proper-

ties at temperatures of 80–95 C.

Pipe coatings generally have acceptable impact resist-

ance of ≥8 J/mm at room temperature and Shore D hard-ness of 75 to 85. The rigid PU coating had a value of

approximately 16 J/mm at Shore hardness of ca. D80. The

rigid PU coating's highly crosslinked density imparts much

lower water absorption than standard coatings and pro-

vides improved anticorrosion properties. The elongation at

break is less than 10 percent which could yield less bend-

ing ability for new coated tubes in the field during the con-

struction of a new pipeline, although it could be reasonable

to bend uncoated tubes first and then apply the coating.

This material is potentially suitable for harsh conditions

like high-ground-water level covering the pipeline, and also

for higher service temperatures (>80 C). Backfilling with the

test coating was done only three hours after application,

which is considerably less than the typical duration. Fur-

thermore, the test coating fulfills several requirements of the international epoxy

standard EN 10289, "Steel tubes and fittings for onshore and offshore pipelines - Ex-

ternal liquid applied epoxy and epoxy-modified coatings" (Table 3).

Rigid Polyurethane Types 2, 3 and 4

Coating types 2 and 3 are standard pipe-coating systems (also applicable for ductile

iron pipes), existing in the market for decades with proven performance. These coat-

ings are typically used for pipelines with service temperatures of up to 60 C and higher – depending on

the formulation. As type 3 is a relatively hard coating, it might be a better option for colder regions with

permanent frost because its increased flexibility could help prevent cracking and coating failure.

Type 4, an elastomeric, might be not a good contender as direct-to-metal pipe coating, especially at

high service temperatures because the crosslinking density is low compared to the others, which has a

direct negative impact on its corrosion protection and cathodic-disbonding properties.

New Raw Materials for Rigid PolyurethaneBy combining the polyols shown in Table 4 with the polyisocyanate pre-polymers shown in Table 5 it is

possible to achieve exceptional anticorrosion properties. The combination of polyol 1 and pre-polymer

1 was tested in the field under real conditions. In addition, it is possible to achieve mixing ratios of 1:1

and 2:1 by volume.

28

Polyol Property Polyol 1 Polyol 2 Polyol 3 Polyol 4

OH content [wt. %] 12.1 14.2 16.7 18.8

Viscosity [mPas] 5,500 5,400 1,800 19,200

Density [g/cm3] 1.06 1.02 1.04 1.02

Average Functionality 3.7 4 3 4

Table 4: New Polyols for Rigid Polyurethane Coatings

Property Pre-Polymer Pre-Polymer 2

NCO content [wt. %] 21.5 24

Viscosity [mPas] 400 220

Density [g/cm3] 1.16 1.17

Table 5: New Polyisocyanate Pre-Polymers for Rigid Polyurethane Coatings

Properties 1 2 3 4

Crosslinked Density very high high medium low

Mechanical Property rigid rigid-hard hard-flexible flexible-soft

Cathodic Disbonding* ++ + 0 - -

Elongation <10% ≥10% ~20–30% >100%

Shore Hardness ≥D75 ~D70 ~D60 <D30

Impact + ++ ++ ++

Bending Properties 0 ++ ++ ++

Adhesion ++ ++ ++ ++

Table 2: Rough Comparison of Solvent-Free, Two-Component Polyurethane Coatings

*at high temperature (>80 C)

Table 3: Requirements of EN 10289 (selection)

Impact resistance 5 J x k x mm (23 C) mm of coating thickness

Adhesion test, pull-off method 7 MPa (23 C)

Cathodic disbonding test Average ≤6 mm, max. ≤8 mm (28d at RT, 2d at 60 C)

Elongation No requirement!


ConclusionPolyurethane pipe coatings are a versatile product class that can be tailored to meet a wide range of

end-use applications. Varying the catalyst, crosslinker and polyol allows the coating formulator to de-

velop a range of properties from elastomeric to rigid. A new class of rigid polyurethane pipe coating raw

materials were developed to meet higher cathodic disbondment requirements and their performance

under harsh, real-world conditions looks promising.

About the AuthorsAndreas aus der Wieschen studied chemistry with a focus on paints and coatings at the University of

Applied Sciences, Krefeld. He joined Bayer AG in 1998 and has overseen the company’s market de-

velopment of polyurethane raw materials for pipeline coatings since 2009.

Dr. Matthias Wintermantel holds a Ph.D. in macromolecular chemistry from the University of Bayreuth,

Germany. Since October of 2012 Dr. Wintermantel has been responsible for product development for

protective coatings, construction coatings and pipe coatings within the EMEA region and Latin America

for Bayer MaterialScience AG.

Todd Williams earned a Ph.D. from the University of Southern Mississippi in 2005 where he wrote his

thesis on alkyd-modified latexes. After a two-year post-doctoral position studying polyurethane coatings

and two years with startup Segetis focusing on renewable polymers, Williams joined Bayer Materi-

alScience developing UV-curable coating formulations. In 2012 he became manager of the company’s

corrosion protection group.

Ahren Olson is the marketing manager for corrosion protection with Bayer MaterialScience LLC in

Pittsburgh, Pa. He has been with Bayer for 10 years, with experience in automotive, construction and

corrosion-protection coatings. He holds a Bachelor of Arts degree with a major in chemistry from The

College of Wooster. Mr. Olson currently provides market development support in Bayer’s efforts to un-

derstand and prevent corrosion for the heavy and light-duty industrial-maintenance markets.

29

JPCL


30

Raw Material Suppliers AnswerCalls for Green and Smart Coatings

Raw MaterialsSuppliers

By Brian Goldie,JPCL

t the end of March 2011, the world’s paint raw material suppliers met at the European

Coatings Show in Nuremberg, Germany.

The bienniel show, which is the largest coatings event in Europe, had a record 26,000

trade visitors this year. Some 890 suppliers to the paint industry from 45 countries displayed their new

and traditional products. At the parallel European Coatings Congress, 650 participants from 40 coun-

tries heard some 150 papers of outstanding interest in the topical issues of this highly innovative sec-

tor.

This review of the exhibition and conference discusses what the developments in new products

and technologies mean to users of protective coatings and what users can expect in new paints or im-

proved performance. The properties described in the review are based on comments and data sheets

from suppliers and have not been independently verified.

A

Photo courtesy of NuernbergMesse© and Thomas Geiger© © 2011-2015 Technology Publishing Co.

31

Trends: Green, Waterborne, and SmartMost new products from coating raw material suppliers at

the show are based on ingredients from renewable or sus-

tainable resources. The concept of “green” products, even

the color theme, was carried over in a number of stand

designs.

The reliance on fossil fuels as sources of raw materials

for coatings is shifting to a reliance on natural products,

with suppliers also being sensitive to the need to not affect

the use of these materials in the human food chain. For

example, suppliers that incorporate soya-based ingredi-

ents into their raw materials are aware of the effects on

the supply of soya ingredients because they are a major

source of nutrition for many countries.

Although new products for high-solids are still in demand,

an underlying trend at the show was an increasing empha-

sis on waterborne systems rather than high(er) solids as a

means of meeting the more stringent regulations on volatile

organic compound (VOC) content in coatings.

A third trend was an increasing number of smart, or

functional, coatings developments on display.

Resins and Curing AgentsThe major raw material suppliers—BASF, Bayer, and Dow—all exhibited their comprehensive prod-

uct ranges for a wide variety of industries.

The industrial coatings market is one of the most diverse that BASF serves, and it introduced two

more products.

• Basonat® LR 9080, a waterborne, fast-drying polyisocyanate mainly for general industrial coatings,

allows faster handling of the coated substrate.

• Acronal® PRO 80, a modified acrylic dispersion for metal primers, not only offers high-performance

corrosion protection but it also is free of alkylphenol ethoxylates (APEO).

APEOs are non-ionic surfactants with an emulsifying and dispersing action that makes them suitable

for a very large variety of applications; however, APEOs, especially nonyl phenol ethoxylates, are

considered very toxic for aquatic life and, in Europe, are no longer allowed or wanted.

Polyurethane coatings formulated with Bayer raw materials are already found in a wide range of ap-

plications; however, the company’s latest developments go even further as coatings increasingly take

on new functions. Bayer’s and other suppliers’ new polyurethane products and developments will be

detailed in the next issue of JPCL.

The Dow Chemical Company’s five businesses combined to demonstrate the benefits of the com-

pany’s latest technological advances in their industries. Dow Construction Chemicals introduced white

reflective roof coatings, a new technology to reduce over-heating in buildings. At the top of most agen-

das in today’s building industry is the drive to create products that are more sustainable and take

maximum advantage of ways to save energy. To this end, one of the main areas promising significant

progress is roof technology, specifically, the development of coatings aimed at lowering building tem-

peratures caused by radiant sunlight.

After many years of study into the indoor temperature effects of direct sunlight, Dow Construction

Chemicals developed and, at the show, highlighted its latest innovations in its “cool roof” technology

Approximately 150 papers were presentedduring the European Coatings Congress. Photos courtesy of NuernbergMesse©.


32

program: reflective elastomeric coatings that are durable

and efficient, with the potential of making the single largest

contribution to reducing CO2 emissions from domestic,

commercial, and industrial buildings. In addition, the cool

roof coatings are designed to play a significant role in ex-

tending the longevity of structural roofing materials.

Another company promoting cool roofing was Arkema.

It showcased its polyvinylidene fluoride (PVDF) resins for

long-life coatings dedicated to cool roofing. The company

also featured its very low VOC acrylic emulsions.

The Huntsman Performance Products division brought

two new fast cycloaliphatic amine-curing agents to the

market. XTA-801 and DCH-99, which offer low viscosity,

low color, and high reactivity, are designed for use in coat-

ings, flooring, and other applications. When combined

with the company’s Jeffamine® polyetheramine (PEA)

hardeners, the new curing agents can enhance glass tran-

sition temperatures, modulus, and hardness, and can im-

prove chemical resistance as well as low temperature

curing properties. The company also introduced a PEA

epoxy curing agent that offers low viscosity, low color, higher glass transition temperatures, and faster

property development than other solutions typically available. Another new product from Huntsman is

a cycloaliphatic amine chain extender for polyurea spray. The extender is designed to be easy to use

and environmentally friendly.

From Wacker came product innovations and customized solutions for industrial coatings, con-

struction, and adhesives and sealants. It also unveiled SILRES® IC 368, a liquid, solventless silicone

resin intermediate for highly weatherable coatings. The new silicone resin is formulated so that an ad-

dition of just 15% increases the UV resistance and weatherability of the organic binder in the coating

system without impairing the mechanical properties of the system.

Lab and open-air weathering tests show that SILRES® IC 368 confers much better gloss retention,

superior weatherability, better heat resistance, and a longer service life compared to similar products.

Designed to be highly versatile, the new intermediate is suitable for modifying alkyd resins, hydroxy-

functional acrylic resins, and hydroxy-functional polyesters commonly used in industrial coatings for

metal, including coil coating.

Perstorp Holding AB’s Voxtar™ is, according to the company, the world’s only renewable pen-

taerythritol platform. Voxtar™ cuts a carbon footprint by up to 75% compared to that of conventional

fossil-based penta and di-penta polyols while providing identical properties and performance. It is

made from bio-based acetic aldehyde and formaldehyde. Combining the renewability of Voxtar™ with

the latest waterborne technology significantly shrinks the carbon footprint of high-solid alkyd paints and

alkyd emulsion paints compared to traditional petroleum-based latex paints.

The product also exemplifies the company’s efforts to reduce emissions and energy consumption

associated with raw material manufacturing—Perstorp uses renewable raw materials such as bio

methanol to decrease the use of petrochemical raw materials. Moreover, renewable energy has been

powering parts of the company’s production sites since 1991, and more than 80% of its R&D work is

focused on environmental innovation.

Perstorp’s approach to innovation is driven by sustainability on three fronts: reducing emissions

and energy consumption in raw material manufacturing; developing products that enable customers

A record 26,000 people attended the exhibition.


33

to formulate low-environmental impact solutions; and

high-performance additives that enable more durable and

long-lasting end products.

Omnova Solutions, together with its recently acquired

Eliokem, is a significant supplier of styrene butadiene lat-

tices, acrylic emulsions, bio-based polymers, and addi-

tives. The company presented a new range of

hydrophobic acrylic emulsions under the Omnapel™

name. The emulsions exhibit exceptional water resist-

ance, good exterior durability, and other resistance prop-

erties, making them useful in water-resistant coatings

such as concrete sealers. In addition, they can be

blended with other polymer systems to enhance water re-

sistance and durability. Some of the products can be used

to create coatings that, when cured above 135 C, are in-

soluble to acids, alkalis, and organic solvents.

Incorez introduced a waterborne epoxy curing agent—In-

corez 148/604— to help companies comply with the re-

quirements of the VOC Solvents Emissions Directive, the

European Union’s main policy instrument for reducing in-

dustrial emissions of VOCs.

Charles Lynch, Commercial Manager at Incorez, commented on the launch: “Our new waterborne

epoxy curing agent is a water soluble polyamine curing agent that is APEO, formaldehyde and solvent

free, and so does not contribute to the VOC levels of the coating formulation. It is designed to produce

very tough and durable, high-gloss waterbased coatings with both liquid and solid epoxy resins. In par-

ticular, this hardener displays very good compatibility with neat Bisphenol A type liquid epoxies, such as

Epikote 828, to provide excellent hardness and cure development.”

Croda Coatings & Polymers brought out its latest “green” innovation, Priamine 1071, for marine

and protective coatings. Priamine 1071 is a low viscosity curing agent for epoxy systems. It can be

used as a main curative and co-hardener, and it addresses a growing demand for the development

of high-solids, low-VOC formulations. Due to its high flexibility and chemical resistance, this novel

dimer diamine, bio-based building block is suitable for interior and exterior coating applications that

require durability under severe conditions. Its sealant and protective properties as well as its improved

adhesion properties can extend the service life of a coating.

Air Products featured its next generation of epoxy curing agents aimed at helping formulators de-

sign coatings solutions that benefit the environment and that are effective over a range of coating ap-

plications. Using its “Total Reactive Technology” approach, the company developed a modified

polyamine curing agent that is 100% reactive (to epoxy resins) and that eliminates the need for a

plasticizer. With its high performance and fast curing at ambient and low temperatures, the techno-

logy has already been successfully used for indoor flooring applications. The plasticizer-free techno-

logy is also more sustainable and has near negligible emissions throughout the lifetime of the coating.

According to experts at Air Products, the new generation technology complements the increasing pop-

ularity of water-based systems.

Additives“Green” again was the word when it came to new additives, but, as stressed by Byk Chemie, no

global standard precisely defines “green” in the context of the surface coating industry. Every-one has

Industry professionals check out new products from suppliers.


a perception of its meaning, and the demand for “green” products keeps growing, hence the number

of new developments. “Green” is also a synonym for “environmentally friendly,” but what does that

phrase mean? According to Byk, the VOC content of products and raw materials is one important in-

dicator of their impact on the environment; however, the deciding factors are often the various eco-

labeling systems in existence and the percentage of renewable materials in a product. Formulators

often have to balance the use and type of “green” materials against performance requirements. With

this in mind, Byk has developed products and technologies that meet current environmental stan-

dards without sacrificing the quality of the products being replaced.

New products on show included Byk-1740, a green defoamer based on eco-friendly and sustain-

able raw materials—vegetable oil derivatives. It is VOC-free and completely sustainable while pro-

viding the same performance as the standard mineral oil-based defoamers. Especially suitable for

waterborne emulsion paints, the new defoamer has no negative influence on color or odor.

Other new Byk products exhibited for waterborne systems included silicone-free defoamers, de-

foamers free of mineral oil as well as silicone, and wetting and dispersing agents.

According to Clariant, it was one of the first companies to offer a 100% APEO-free alternative for

manufacturing binder emulsion polymers. In addition to its low VOC levels, Emulsogen® EPA 073 is

now one of few anionic emulsifiers with FDA approval. When combined with nonionic emulsifiers like

Emulsogen LCN 287 or Emulsogen LCN 407, these APEO-free emulsifiers offer increased latex sta-

bility and better shelf life. They increase the availability of more environmentally acceptable alterna-

tives to solvent-borne paints and coatings in contact with foodstuffs.

Rhodia is also moving toward more sustainable coatings with its portfolio of breakthrough per-

formance additives created to meet formulators’ demands for specific solutions for creating the next

generation of eco-friendly coatings. The company highlighted its new eco-friendly evaluation ap-

proach to designing sustainable coatings by spotlighting its growing line of zero-VOC, APEO-free

performance additives and solvents for waterborne coating. Rhodoline® OTE is a novel zero-VOC,

APEO-free range of additives for extended open time (workability) in waterborne coating formula-

tions. It provides a two- to four-fold increase in open time without the addition of solvents, thus giv-

ing painters longer to work overlays seamlessly or to touch up paint to correct imperfections such as

drips and brush marks.

Air Products launched a new range of defoamers and de-aerators based on organic, silicone, and

molecular chemistry that will allow manufacturers to produce high-performance coatings that are

more durable, efficient, and environmentally friendly. The defoamers and de-aerators are particularly

useful for waterborne systems and can be used in floor coatings in combination with the company’s

epoxy curing agent technology.

BASF also featured Dehydran® SE 2, a high-performance silicone polymer emulsion defoamer for

premium waterborne paints and clear coats. It offers good foam suppression and long-term persis-

tency, is highly compatible and easy to handle, and minimizes gloss reduction. Because Dehydran®

SE 2 is VOC-free and has an ultra-low semi-volatile organic compound (SVOC) content, it also helps

manufacturers formulate paints and clear coats that meet the requirements of environmental stan-

dards and safety certifications, such as the German TÜV, Green Seal GS-11, the EU Ecolabel, and

the Blue Angel.

In the range of rheology modifiers, BASF introduced DSX® 3801, a VOC-free, mid-shear rheology

modifier with excellent ICI thickening. The ICI build of the thickener clearly exceeds that of benchmark

waterborne products, even at lower dosages. Due to the high efficiency and improved performance

of DSX® 3801, a smaller amount of it is needed in formulations—a “do more with less” approach that

delivers sustainability benefits.

Dow Coating Materials announced the launch of its new EVOQUE™ Pre-Composite Polymer Tech-

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nology—a revolutionary development for paints and coatings that promises to change the way for-

mulators think about hiding and the use of titanium dioxide (TiO2). The acrylic-based technology im-

proves the particle distribution and light scattering efficiency of TiO2, facilitating improvements in

hiding efficiency and allowing for up to 20 percent less TiO2 used in the formulation. Additional ben-

efits include improved barrier properties such as stain and corrosion resistance.

Depending on their formulation goals, paint manufacturers can choose to reduce TiO2 content or

improve hiding while they improve paint performance. The Pre-Composite Polymer Technology may

also help formulators reduce the carbon footprint of their end products by reducing the energy foot-

print that comes from mining, processing, and transporting TiO2 to their formulation plants. Dow Coat-

ing Materials is conducting a life cycle analysis, which will be verified by a third party, to quantify the

full spectrum of sustainability advantages that may result from using its new technology.

PigmentsThe trend for “green” products also extended into the new pigments offered from the various suppli-

ers. The developments were predominately in color pigments, although some new environmentally

friendly anti-corrosion pigments were on show from companies such as Halox, Nubiola, SNCZ,

Sachtleben, and Pigmentan.

Smart CoatingsOne class of “smart coatings” are the self-healing systems that incorporate Bayer MaterialScience

products. The systems are functionalized anti-corrosion coatings or topcoats that can “heal” dam-

age autonomously, similar to the self-healing mechanism of the human skin.

Other products for smart coatings were for graffiti resistance.

New perspectives for smart coatings are being found in marine coatings with the use of carbon

nanotubes, again from Bayer MaterialScience. The nanotubes allow another approach to provid-

ing different properties and additional functions, and their use as coating additives could open up

even more intriguing perspectives. The high mechanical strength and electrical conductivity of

the particles, in particular, promise novel possibilities for formulating coatings and for improving

the strength of structural components while keeping their weight extremely low. Novel epoxy-gel

coatings with nanotubes are already significantly improving the scratch-resistance of coatings for

ship hulls.

Nanotechnology is also being used to give floor coatings with improved properties. The COL.9®

nano-based binder from BASF, which has been used to produce “self-cleaning” wall coatings, can

also be used to coat substrates such as concrete, stone, or tiles. This means that, for example, tire

marks or oil stains on garage floors can be a thing of the past. The functional principle is the same

for both facade and floor applications. The binder combines the benefits of synthetic resin disper-

sions with those of silicates. (COL.9 is a dispersion of organic polymer particles in which nanoscale

particles of silica are incorporated.)

The organic part of the binder, i.e., the acrylic resin, ensures sufficient elasticity while the mineral

part lends the colored coating the required rigidity. This makes coatings particularly resilient as well

as resistant to dirt and chemicals.

CongressThe themes at the show were also prominent at the parallel. In fact, the plenary lecture by Professor

Matthias Beller, University of Rostock, Germany, was “Sustainable chemistry: A key technology for the

21st century,” which addressed the improvement of industrial chemicals production. Approximately

150 papers were presented in 25 sessions covering a range of technologies and end uses, with specific

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Dr. Matthias Beller addressed sustainable chemistry in his keynote speech.


sessions on sustainability and bio-based coatings, smart coatings, and nano-technology. The majority

of new products on show were also the subject of detailed technical presentations.

SummaryThe emphasis of the products being exhibited and technologies presented was on their environmen-

tally friendliness, with materials for waterborne systems predominating. Companies were also keen

to explain their desire to use renewable ingredients as their raw material sources and their efforts in

reducing the carbon footprint of their production facilities.

Brian Goldie, technical editor for JPCL, has worked with protective coatings for many years,

including in the oil industry.

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JPCL


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