Rheology leadership plus so much more...

Key Benefits

Optimized workability by reduced stickiness Superior sag and storage stability Partial replacement of cellulose ether

BENTONE®

DS

Economical, highly efficient and refined Hec-torite clay grade with excellent balanced per-formance for pasty, emulsion based render-

ings

Application Leaflet February 2015

Innovation ● Compliance ● High Performance

2

Introduction

Pasty, emulsion based renderings are typically used as finishing systems for wall applications. This mo-dern product technology is combining performances, such as good water stability and weather resistance with the properties and durability of mineralic systems. Further, emulsion based renderings can be tinted using colourants to enhance the optical aspects of the treated object.

To adjust and control viscosity, water retention and open time, cellulose ethers are typically being used. However, unwanted side effects of the cellulose ethers are the poor application properties and the strong tackiness on the tools. As these kind of renderings are typically being applied by hand, using a trowel, the lowest possible stickiness, resistance to flow and excellent workability are desired.

The Hectorite based rheology modifier BENTONE® DS has been de-signed to enhance the application properties of emulsion based ren-derings by reducing the resistance and stickiness on the tool. BEN-TONE® DS strongly increases the low shear viscosity and flow point of the rendering. This typically results in improved sag control and stability. Additionally, a remarkable reduction of the cellulose ether content can be achieved by using BENTONE® DS in the formulation. This does not adversly affect the open time. Moreover, the inclusion of BENTONE® DS reduces the water sensitivity.

In this leaflet, the outstanding performance of our Hectorite based BENTONE® DS in comparison to unrefined Hectorite clays is display-ed.

Key Benefits

Easier application due to reduced resistance and stickiness

Excellent sag and slump control

Optimum storage stability due to increased elasticity

Less water sensitivity

Partial replacement for cellulose ether

No adverse affect on open time

Chemical and Physical Data Incorporation & Levels of Use

BENTONE® DS is easy to process and is typically

recommended to be added under stirring to the

water first. Than it should be mixed at the highest

practicable speed for minimum 10 minutes to

ensure sufficient hydration and delamination.

Subsequently, all other ingredients can be added

and incorporated to complete the formulation.

Typical levels of additions for BENTONE® DS are

between 0.2% and 2.0% by weight on total

formulation. However, depending on the degree of

suspension or the desired rheological

characteristics as well as which type of cellulose

ether is being used, the ultimately required amount

might differ.

Composition Refined, beneficiated natural

hectorite clay

Colour/Form Milky-white, soft powder

Solids content [%] 100

Density [g/cm3] ca. 0.4

Particle size < 74 µm 93

3

Test Formulation

The comparison study was performed in two parts.

In the first part, the individual clay additives were ad-

ded a fixed quantity of either 0.15% or 0.3%. In the

second part of the study, the required amounts to

achieve a flow table value of 16.5% were formulated.

Formulations with 0.4% cellulose ether as a stand-

alone thickener are mentioned as blank. In case of

clay containing examples, the cellulose ether concent-

ration has been reduced by 25% to a loading level of

0.3%.

Practical examples

Part 1: Clay based rheology modiers formulated at equal concentration

Flow characteristics

The rheograms below display the flow behaviour of rendering formulations with fixed clay concentrations.

BENTONE® DS provided significantly higher low-shear viscosities at both tested concentrations, 0.15%

and 0.3%, than the natural, unrefined Hectorite, when formulated alternatively to 25% of the original cellu-

lose ether content. The natural Hectorite grade causes only marginal changes to the blank with originally

formulated 0.4% cellulose ether.

Test System and Practical Examples

Emulsion based rendering

Compound Concentration [%]

Water 10.7 - X

Clay based additive X (0.3 or 0.15)

Disperse for 10 minutes at 16 m/s

Na-polyphosphate, 10% 0.3

NUOSPERSE® FX 504 0.3

DAPRO® DF 7005 0.1

Biocide 0.2

Titanium dioxide 4.0

Disperse for 10 minutes at 6m/s

VAE based binder emulsion 13.2

Coalescing agent 1.3

Sodium hydroxide solution, w (NaOH) = 0.1

0.2

Blend for 15 minutes in the Hobart-mixer

Calcium carbonate fillers (various particle size)

69.4

100.0

4

Flow point measurement

The flow point was determined by extracting the shear stress necessary to exceed a damping factor/tan

delta value of 1 from an amplitude sweep oscillation test. Exact test description can be found in the Ap-

pendix.

The formulations with BENTONE® DS displayed noticeably higher shear stress to exceed a tan delta value

of 1 in comparison to the natural, unrefined Hectorite grade formulated at equal concentration. This value

is defined as the flow point.

However, as it might be difficult to read from the graph, the relevant values have been extracted and plot-

ted in the following chart on the next page.

Practical Examples

5

Sag control versus flow point

Sag resistance (SR), defined as the maximum applicable layer thickness, was determined with a wedge

blade application. The flow points (FP) were extracted from the above amplitude sweep curves.

At a concentration of 0.15%, BENTONE® DS provided a slightly higher sag stability and flow points than

the blank with only cellulose ether. The use of the natural unrefined Hectorite clay grade resulted in only

marginal performance differences compared to the blank at these concentration.

At 0.3%, BENTONE® DS clearly outperformed the unrefined, natural clay product on sag stability and flow

point.

Open time

All rendering formulations containing a clay rheology modifier showed slightly longer open time compared

to the blank formulation with pure cellulose ether.

Practical Examples

6

Part 2: Flow performance at equal consistency adjusted to the relevant clay

quantity

Required concentration

The concentration necessary to achieve a flow table value of 16.5 cm is displayed below. The use of BEN-

TONE® DS allows the use of noticeably lower loadings to obtain a flow table value of 16.5 cm when repla-

cing 25% of the originally formulated cellulose ether portion.

Flow characteristics

The rheogram below displays the flow behaviour of rendering formulations at equal flow table values of

16.5 cm. The formulation with BENTONE® DS showed significantly higher viscosities at low shear rates in

comparison to the formulation containing the natural, unrefined Hectorite clay.

Practical Examples

7

Flow point measurement

The flow point was determined extracting the shear stress required to exceed a damping factor/tan delta

value of 1 out of an amplitude sweep oscillation test. Exact test description can be found in the Appendix.

Both formulations with either BENTONE® DS or the unrefined, natural Hectorite clay provided comparable

flow points when adjusted to equal consistency. Both formulations clearly outperformed the blank formula-

tion with only cellulose ether.

However, as it might be difficult to read from the graph, the relevant values have been extracted and plot-

ted in the following chart.

Sag control versus flow point

Sag resistance (SR), noted as the maximum applicable layer thickness, was tested with a wedge blade

application. The flow points (FP) were extracted from the amplitude sweep curves on the previous page.

Both formulations with Hectorite clay performed similar with respect to the flow point. BENTONE® DS pro-

vides slight advantages with respect to the maximum applicable layer thickness when adjusted to equal

consistency. Both clay modified renderings clearly outperformed the blank formulation only containing cel-

lulose ether.

Practical Examples

8

Structure recovery

The structure recovery test was determined by an oscillation test at fixed amplitude and frequency. Exact

test description can be found in the Appendix. Both formulations displayed a very similar structure

recovery after the removal of shear.

Open time

All rendering formulations containing clay demonstrated slightly longer open times compared to the blank

formulation.

Practical Examples

9

Ease of application/Workability

The use of clay in both cases resulted in significantly improved workability, less resistance and stickiness

on the tool. The required loading level of BENTONE® DS to achieve this effect is noticeably lower than

with the unrefined, natural Hectorite grade.

Water sensitivity

The displayed water sensitivity is related to softening of the readily cured rendering on the relevant sub-

strate when exposed to water.

All tested cured plaster formulations performed equally good when exposed to water.

Practical Examples

10

Conclusion

When used at equal concentrations to replace 25% of the originally formulated cellulose ether quantity, the refined

Hectorite grade BENTONE® DS provides much stronger viscosity build, flow point and sag resistance than the unre-

fined, natural Hectorite grade.

To adjust the renderings consistency to equal flow table values of about 16.5 cm, BENTONE® DS requires much

lower loadings than unrefined, natural Hectorite grade to replace 25% of the original cellulose ether portion. Using

the individual quantities to equalize the consistency, the performance of the renderings with respect to low shear vis-

cosity, sag control, flow point, workability and water sensitivity is comparable with both, BENTONE® DS and the un-

refined, natural Hectorite grade.

In comparison to the blank, containing only cellulose ether, the use of either BENTONE® DS or the natual Hectorite

clay, results in significantyl improved low shear viscosity build, sag stability and workability.

Appendix

Test methods

The flow table value was measured with the Haegermann flow table desk (DIN 18555, Part 2) when the table

was dropped 15 times within 15 seconds. The lower the resulting value, the higher the viscosity.

To test the sag resistance the renderings were applied with a wedge shaped blade (0-3 cm height) on gypsum

plasterboards and stored vertically until cured. The maximum film thickness without sagging was recorded.

The rheological characteristics (rheograms) were determined with the Anton-Paar MCR 300 rheometer, mea-

suring geometry CC 27-P7 (bob and cup system, profiled) at a temperature of 23°C.

Flow points were determined with a Anton-Paar MCR 300 rheometer, measuring geometry CC 27-P7 (bob

and cup system, profiled), at a temperature of 23°C. The test was performed as an amplitude sweep. Therefo-

re the shear stress was increased from 0.1Pa to 100 Pa at a fixed angular frequency of 10 s-1

. The shear

stress when the damping factor (tan delta) exceeded the factor of 1 was extracted and noted as the flow point.

Structure recovery was measured using the Anton-Paar MCR 300 rheometer, measuring geometry CC 27-P7

(bob and cup system, profiled), at a temperature of 23°C. The test was performed in three individual ocillation

parts:

Step 1: 50 seconds at a strain of 0.1% and an angular frequency of 10 s-1

.

Step 2: 10 seconds at a strain of 10% and an angular frequency of 10 s-1

.

Step 3: 4 minutes at a strain of 0.1% and an angular frequency of 10 s-1

.

Workability or application properties were evaluated by applying the rendering with a smooth trowel on a verti-

cal wall. The stickiness on the tool and the force required during the application were subjectively assessed.

To evaluate the water sensitivity the renderings were applied on fibre concrete plates in a film thickness of 3

mm. After drying, the plates were stored for two hours in water. Soaking and rehardening were determined

visually.

To test the open time, the plaster was applied at a layer thickness of 3 mm on fibre cement plates. The period

from the application until the the surface was not tacky anymore, was recorded as open time..

Elementis UK Ltd

c/o Elementis GmbH

Stolberger Strasse 370

50933 Cologne, Germany

Tel: +49 221 2923 2066

Fax: +49 221 2923 2011

Elementis Specialties Asia

No. 99 Lian Yang Road

Songjiang Industrial Zone

Shanghai 201613

P.R. China

Tel: +86 21 57740348

Elementis Specialties, Inc.

469 Old Trenton Road

East Windsor, NJ 08512

USA

Tel: +1 609 443 2500

Fax: +1 609 443 2422

Learn more about our products

and visit our website!

www.elementis-specialties.com

or email us at:

waterinfo@elementis.com