1

EXPERIMENT 1

Compounding of elastomer using two roll mill.

INGRIDIENTS FORMULATION Natural Rubber NR 100 phr

Carbon Black 60 phr

Silica 50 phr

Sulfur 1.5phr

Dibenzthiazyal-disulfide MBTS 2 phr

Tetramethylthiurum-disulfide TMTD 1 phr

Anti-degradent 1 phr

ZnO 2 phr

Steric acid 1 phr

Processing oil 10 phr

Procedure

Weigh all the ingredients which are required for the making of a sheet of compound (i.e. natural

rubber).

Convert the all formulations from Parts per Hundred PHR into grams, multiplied by with factor 5

for easy balance.

Take the weighted elastomer i.e. Natural rubber bring it to the two roll mil and wrap it on the roll

until its viscosity reduced slightly due the shearing action between the two rolls.

Incorporate the fillers (carbon black and silica) and mix them.

Add processing oil in this mixture to make the mixing process easier.

Mix all rest of the ingredients and it into the elastomer which is banded onto the roll and mix it

for 2-3 minutes.

Homogenize it and sheeting out the compound.

Theory

Natural Rubber

Rubber is an example of an elastomer type polymer, where the polymer has the ability to return to its

original shape after being stretched or deformed. The rubber polymer is coiled when in the resting state.

The elastic properties arise from the its ability to stretch the chains apart, but when the tension is released

the chains snap back to the original position.

Natural rubber is a type of polymer that is obtained as a milky white fluid known as latex from a tropical

rubber tree. Natural rubber is from the monomer isoprene (2-methyl-1,3-butadiene). [1]

2

Carbon Black

Carbon black [C.A.S. NO. 1333-86-4] is virtually pure elemental carbon in the form of colloidal

particles that are produced by incomplete combustion or thermal decomposition of gaseous or liquid

hydrocarbons under controlled conditions. Its physical appearance is that of a black, finely divided pellet

or powder. Its use in tires, rubber and plastic products, printing inks and coatings is related to properties

of specific surface area, particle size and structure, conductivity and color

Traditionally, carbon black has been used as a reinforcing agent in tires. Today, because of its unique

properties, the uses of carbon black have expanded to include pigmentation, ultraviolet (UV) stabilization

and conductive agents in a variety of everyday and specialty high performance products. [2]

Silica

Amorphous precipitated silica, defined by a specific CAS number, is used in many applications in addition

to its use in the rubber and tire industry, including cosmetics, paper and many other applications related

to nutrition and health.[3]

Silica have been used as the main reinforcing fillers that increase the usefulness of rubbers. As a

reinforcing agent, anti-aging agent, silica can be used in rubber products to increase strength, toughness,

anti-aging, anti-friction of rubber products and prolong life and other functions.[4]

Sulfur

Sulfur is one of the principal rubber vulcanizing agents. It is a critical additive. When chemically combined

with rubber, sulfur develops basic performance properties in the vulcanized compound such as: tensile

strength, elongation, modulus, and hardness.

The most stable molecular form of sulfur at ambient conditions is a ring structure containing eight sulfur

atoms. Depending on conditions these molecules orient into one of two crystalline structures. At room

temperature the crystals are rhombic and above 95C they rearrange to monoclinic. Less than 1.5 % of

either crystalline structure of sulfur is soluble in any rubber at room temperature.

The second common molecular form of sulfur is polymeric sulfur, made up of unbranched chains of sulfur

atoms. It is commonly referred to in the rubber industry as insoluble sulfur. When this material is created

by rapid heating to above 160C and quenching to room temperature, the sulfur is amorphous. If formed

under other conditions, the polymer chains may develop regions of pseudo crystallinity.

Insoluble sulfur is an important form of sulfur used only in the rubber industry. It is not soluble in any type

of rubber hydrocarbon. When it is mixed in rubber, it disperses but remains undissolved in the rubber.

The use of insoluble sulfur prevents the development of a supersaturated solution of sulfur in rubber that

occurs when rhombic sulfur is used. No sulfur bloom will develop on the surface of uncured rubber pieces

when the rubber cools after mixing or processing; therefore, building tack is preserved. At curing

temperatures, insoluble sulfur rapidly transforms to a soluble species, dissolves in the rubber, and enters

into the vulcanization process.[5]

3

Dibenzthiazyl- Disulfide (MBTS)

It is a Delayed-action semi-ultra accelerator. MBTS are used for rubber and latex vulcanization

acceleration. The amount of MBT in MBTS may be of importance in predicting performance in rubber

compounds and for raw material purchase and control.ASTM D4818-89)

Tetramethyl Thiuram Disulfide (TMT, TMTD)

TMTD can be used as a single accelerator, as a secondary accelerator or as a sulfur donor in most sulfur-

cured elastomers, heat aging and compression set resistance. Good color retention is obtained in non-

black vulcanizes. It is a Ultra-accelerator and vulcanizing agent

Zinc oxide-ZnO

Zinc oxide (ZnO) - is the most known vulcanizing activator and it can be used along with the majority of

known accelerators. Thus, vulcanization in the presence of ZnO leads to a decrease of the sulfidic

crosslinks, while the formation of C-C bonds is favored. This is accompanied by an increase of the thermal

stability of vulcanizates. During the vulcanization in the presence of ZnO, sulfur is partially converted to

zinc sulfide.

Antidegradents

Antidegradant describe materials used in rubber to protect against the effects of oxygen and ozone.

Materials that fall in this general category include both antioxidants and antiozonant. [6]

Steric acid

Stearic acid is important in the rubber vulcanization process. It is believed that the stearic acid reacts with

zinc-oxide or other metallic oxides, during vulcanization, to form a rubber soluble salt or soap that reacts

with the accelerator enabling it to exert its full effect. Because of the Dual nature of Hydrophobic and

hydrophilic nature of the Stearic Acid, it becomes more rubber soluble and this property will be very

helpful in the Activator system of the rubber compounding

Stearic acid of commerce is generally a mixture of palmitic, stearic, and oleic acids usually derived from

tallow base stock but can be derived from other fats and oils of animal or vegetable origins.[7]

Processing oils

Various oils are used to help incorporate all the dry ingredients used in the rubber compounding. They

also help to reduce the viscosity of the overall compound to help with molding. Adding more oil can also

lower the hardness of the rubber. Thus, lower Shore A compounds will typically have more oil in the

formulation.

Two roll mill

Two roll mill consists of two horizontal, parallel heavy metal rolls which can he jacketed with steam and

water to control the temperature. These rolls are connected to the motor through gears to adjust the

speed. Rolls turn towards each other with a preset adjustable gap or nip o allow the rubber to pass through

to achieve high shear mixing. Mill mixing is the oldest method of rubber mixing, dating back to the very

4

beginning of the rubber industry. However, it is a relatively slow method and its batch size is limited.

Internal mixers overcome these problems.[8]

Figure: Two roll rubber mixing mill

Friction ratio

The speed of the two rolls is often different. The back roll usually turns at a faster speed than the front

roll, this difference increases the shear force. The difference in roll speeds is called friction ratio, which is

dependent upon the mill s use. For natural rubber mixing a ratio of 1: 1 .25 for the front to back roll is

common. [8]

Cooling

Cooling is employed either through cored rolls or through peripherally drilled rolls. The principal one

employs cored rolls i.e. water is sprayed onto the outside of an axially drilled central core. [8]

Other attachments

Mills are fitted with a metal tray under the rolls to collect droppings from the mill. Guides are plates which

are fitted to the ends of the rolls to prevent the rubber from contamination with grease etc. Safety

measures arc also attached to the mill for protecting the operator as well as the mill. [8]

Observations

Mixing process

There are five stages in the mixing process. These are:

5

Banding/wrapping the rubber on the first roll

Viscosity reduction by mastication

Incorporation of ingredients

Distribution

Dispersion

When a highly elastic rubber of high molecular weight is fed into the mixer, it must be converted to a state

in which it will accept particulate additives. This stage is called viscosity reduction. It is achieved either by

a physical mechanism called mastication or by chemical means called peptisation. Now the rubber is ready

to flow around the additives, incorporating and enclosing them in a matrix of rubber. Incorporated

additives are then available for distribution. For better incorporation and distribution, with the help of a

cutting knife give suitable cuts from either sides of the front roll.

During distributive mixing the rubber flows around the filler particle agglomerates and penetrate the

interstices between particles in the agglomerate and the rubber mix becomes less compressible and its

density increases. The rubber which has penetrated the interstices becomes immobilized and is no longer

available for flow. This immobilization reduces the effective rubber content of the mixture. The

incompressibility of the mixture allows high forces to be applied to the particle agglomerates, causing

them to fracture. This action is called dispersive mixing, which serves the purpose of separating the

fragments of agglomerates once they have been fractured. The addition of plasticizers facilitates easy

incorporation of the fillers. Curatives are added at the end of the mixing cycle. After thorough

incorporation of all the ingredients the mix is homogenized and the batch is then sheeted out. For best

mixing procedure the temperature is kept at 75-80 C by careful adjustment of flow of cooling water

through the rolls.

Comparison before and after NR

No. Before making NR

compound After making NR compound

1 Surface is not smooth Surface become smooth

2 On touching it gives black color It does not give color

3 Flexible Hard and rigid

4 Dull black color Shiny black color

5 Less elastic Comparatively less plastic and high elastic

6 No additive No agglomeration of additive

7 Good distribution and dispersion

8 No blooming due to sulfur

No bubbles on the surface due to air entrap

6

EXPERIMENT 2

Fabrication of extruded profile by extruder.

Extruders

Extruders for processing elastomers normally provide most of the energy for heating the material by

energy transfer through the screw from the drive unit. Thus, such extruders operate nearly adiabatic.

These extruders are also usually equipped with external thermal control, which because of the relatively

low operating temperatures (130 C max), is often carried out with pressurized water. This arrangement

allows the extruder to be preheated to the required temperature before start-up. In elastomer processing

one makes a basic distinction between hot- and cold-feeding.

Figure: Extruders for Elastomers

Hot Feeding

In hot-feeding, the rubber compound slaps which have been stored, are reheated to 60 to 100 C and

plasticized on one or more roll mills: this transforms the rubber mix into a fully flow able state by heat

transfer, or input of mechanical energy. The extruder is continuously fed with strips, or discontinuously

with pigs of this plasticized mix. The extruder still has to move the material against the resistance of the

forming die, during which process further plasticization can occur. As a consequence of the relatively

modest demands made on the extruder, hot-feed machines have a small L/D (screw length to diameter)

ratio, usually between four and six. Because of its short length the hot-feed extruder is relatively sensitive

to changes in the feed, which translate immediately into variations in the geometry of the extruded

profile. For producing blanks, discontinuous ram extruders are used, as well as hot-feed screw extruders.

7

Cold Feeding

In cold-feeding, the extruder is fed at room temperature with a plasticized compound. The feed material

may be strips or granules. Since with cold-free extrusion both heating and plasticization functions must

be carried out by the extruder, the length of the screw is greater than with hot-feed extruders. The L/D

ratio varies with screw diameter, and lies between 18 and 22. For special tasks extruders with even greater

L/D ratios have been produced. In recent years cold-feed extruders have been adopted in almost all areas

of rubber extrusion, since, by comparison with hot-feed operations, processing is significantly more

economic as preheating roll mills are not required.

The functions a cold-feed extruder has to perform may be summarized as follows:

Feeding. conveying, and compacting,

Heating and plasticization,

Mixing and homogenization,

Pressure build-up for extrusion.

Observations

We are using cold feeding for natural rubber compound these compounds are cut into strips and is fed

into the extruder. This extruder is a single zone conveying extruder, no external heating is required

material gets heated due to viscous heat dissipation owing to its viscoelastic nature, die is slightly heated

for shaping the material. When the desired shape of the material is obtained then the profile is heated in

the oven at 140oC for curing for about 40 minutes.

Comparison before and after curing

Sr. Before Curing After Curing

1 Slightly rough surface Smooth surface

2 Bubble on the surface of strips No bubbling over the surface

3 Less hard More hard and rigid

4 Flexible Tough

5 Dull black color Shiny black color

6 No crosslinked network Crosslinked network formed

8

References

1. Ophardt, C.E., Rubber Polymers, in VirtualChem Book2003. 2. Robertson, J.a.K.I. Carbon Black. 2004. 3. Kraus, G., Reinforcement of Elastomers by Particulate Fillers, in Science and Technology of Rubber,

B.E.a.F.R.E. James E. Mark, Editor 1978: new york 4. N. Rattanasom, T.S.a.C.D., Reinforcement of natural rubber with silica/carbon black hybrid filler.

2007. 26(3). 5. D4528, A., Standard Classification for Rubber Compounding MaterialsSulfur, in Significance and

Use2012. 6. D4676-94, A., Standard Classification for Rubber Compounding MaterialsAntidegradents, in

American society for testing and materials(ASTM)1994. 7. 88, A.D.-. Standard Classification for Rubber Compounding MaterialsStearic Acid, in Significance

and Use2012. 8. P. M. Visakh, S.T., Arup K. Chandra, Aji. P. Mathew, Advances in Elastomers I: Blends and

Interpenetrating Networks, in Two roll mill, Springer.

9

EXPERIMENT 3

Curing of the Elastomer by hot press and giving it the desire shape.

Procedure

The procedure of curing the rubber compound is given below:

First of all for giving a shape to the rubber compound select the type of the Mold.

Switch on the Hot Press machine and the set the temperature of the machine at about 140oC.

Then set the temperature of upper controller up to 290oF and lower controller to 190oC and preheat the mold for 1 hour.

Cut the rubber compound into small strips.

Rubber strips are introduced into the mold in a partially cured condition. Gradually increase the pressure of the hot press from 0 to 200 Bars.

Remove the mold from the machine after 50 minutes and open the mold and take the sheet of rubber from the mold. Cool it and observe the properties of cured product.

Observations

We are curing natural rubber compound, rubber is cut into strips and is fed into the pre-heated mold for

giving it the shape of sheet. Leave it for 1 hour to attain a constant temperature of 140oC. The desired

shape and curing is not achieved because temperature is not sufficient for the given time so when we

removed our material from the mold it was sticky and tacky and it also gave color. Very few changes were

observed. The material which was placed in the corners of the mold attained the shape of ring, and the

material which was placed in the center didnt attain the shape of the ring.

Comparison before and after curing of the rubber compound

Sr. Before Curing After Curing 1 Slightly rough surface Smooth surface

2 Bubbles on the surface of strips No bubbling over the surface

3 Less hard More hard and rigid

4 Flexible Tough

5 Dull black color Shiny black color

6 Uncured Cured

7 Stretched No stretch-ability

10

EXPERIMENT 4

Blending of Polychloroprene and Styrene Butadiene Rubber in internal batch mixer.

INGRIDIENTS FORMULATION PolyChloroprene 30 PHR

Styrene Butadiene Rubber 70 PHR

Silica 30 PHR

Sulfur 1.5 PHR

Dibenzthiazyal-disulfide MBTS 2 PHR

Tetramethylthiurum-disulfide TMTD 1 PHR

Anti-degradent 1 PHR

ZnO 2 PHR

Steric acid 1 PHR

Processing oil 5 PHR

Procedure

First of all to convert the formulation from Parts per Hundred PHR to grams multiply with the

factor 0.19 for easy calculations.

Weigh all the ingredients which are required for the blending of PolyChloroprene and Polystyrene

Butadiene Rubber.

Switch on the Internal Mixer and set its temperature to 50oC and 45 RPM

Take the weighted Elastomer i.e. Styrene Butadiene Rubber in internal batch mixer

Add processing oil to make the blending process easy, and allowed to process for almost 2 minutes

into the internal mixer

Add Polychloroprene and blend them for 2 minutes

Incorporate silica and mix it for 2-3 minutes and give extra time almost 7 minutes for the blending

in chamber.

Mix all rest of the ingredients and add it into the blend in the chamber of internal mixer and mix

it for 2 minutes.

Homogenize it and remove the blend from the Chamber.

Observations and Theory

Polychloroprene

Among the specialty elastomers polychloroprene [poly(2-chloro-1,3-butadiene)] is one of the most

important with an annual consumption of nearly 300,000 tons worldwide. CR is not characterized by one outstanding property, but its balance of properties is unique among the synthetic elastomers. It has:

Good mechanical strength

High ozone and weather resistance

Good aging resistance

11

Low flammability

Good resistance toward chemicals

Moderate oil and fuel resistance

Adhesion to many substrates

Styrene-Butadiene Rubber

Styrene-butadiene rubber (SBR), a general-purpose synthetic rubber, produced from a copolymer of

styrene and butadiene. Exceeding all other synthetic rubbers in consumption, SBR is used in great quantity

in automobile and truck tires, generally as an abrasion-resistant replacement for natural rubber (produced

from polyisoprene).

Blending process

There are five stages in the blending process. They are:

Enter the Elastomers into the mixer chamber in which materials are to be mixed

Mixing is achieved by deforming the heat softened batch of feed by rotating blades

Incorporation of ingredients

Distribution

Dispersion

Observations

Greyish color

Soft when it is removed from the mixer but gets harder on cooling

It does not give color upon touching its surface

Hard and rigid

Less stretch-ability

No agglomeration of additive

Good distribution and dispersion

No blooming due to sulfur

No bubbles on the surface due to air snare

12

EXPERIMENT 5

To find the bound rubber content of cure rubber compounds.

Procedure

The procedure for determining the bound rubber content and crosslink density of a cure rubber

compound is given below:

First of all take round sample of cure rubber and weigh the sample.

Place the round rubber sample in a glassware with toluene approximately 30 ml, and make sure that the rubber sample is completely covered then close the jar tightly.

Leave the jar for 3 hours as it is, then take the rubber sample out from the toluene jar.

Wipe toluene from the rubber, blot dry and weigh it.

Place the rubber sample in jar for 24 hours and after 24 hours remove the rubber sample, dry it and weigh it again.

Put the rubber sample again into the jar for 24 hours and weigh it after wiping the toluene from rubber, mass will increase with time and after certain period of time it will be constant and then the mass doesnt increase further.

Repeat the process and weigh it until mass became constant.

Take the sample and place it in the fume hood for 1 day at atmospheric pressure.

Put the sample in oven for 1 day at 85oC.

Place the sample for drying at atmospheric pressure for 1 day.

Weigh the dried sample again and we will get a particular weight and this would be known as Gel.

Use Flory Rehners equation to determine the bound rubber contents.

Theory

We can also determine crosslinking density, volume fraction and swell ratio from this experiment.

An extension to FH is well known as a method of estimating crosslink density through swelling measurements, using the FloryRehner equation.[1]

Where,

= volume fraction of the polymer in the swollen system,

Volume swelling ratio, S=1/

m= crosslink density (mole/volume)

13

V= molar volume of the solvent,

= FloryHuggins parameter representing the solventpolymer interaction energy.

Typical use of this equation is to measure the crosslink density by measuring the swelling induced by a solvent of known . More detailed calculations of swelling in cross-linked polymers have been developed, but the FloryRehner equation is simple one.

If necessary, a FH parameter can be calculated from the more widely known solubility parameters, i, for the solute and solvent.[1]

FH interaction parameter

d Solubility parameter dispersion

p Polar

h Hydrogen bonding components

Volume fraction

The volume fraction of rubber in the swollen network is determined by using: [2]

Vr the volume fraction of rubber in the swollen network

a1 the weights of the swollen specimen

a2 the specimen after drying at room temperature

r density of rubber

s density of solvent

14

Bound Rubber Content

Bound rubber is the rubber portion that can no longer be separated from the filler when a rubber batch is extracted in a good solvent over a specific period of time, usually at room temperature. It is a measure of the interaction between the polymer and the filler. During the milling process, polymer chain molecules become attached to reinforcing fillers. Therefore they are no longer soluble in usual solvents. This process is the basis for the formation of bound rubber. It continues after mixing and eventually a system of interconnecting chains and particles results, which appears as an insoluble fragile gel containing filler and part of the bound rubber. [3]

Equation that is used to calculate the bound rubber content is: [4]

Rb, bound rubber content

Wfg, weight of filler and gel

Wt, weight of the sample

mf, fraction of the filler in the compound

mr, fraction of the rubber in the compound

Sample

NBR round shape piece is taken as sample to determine its crosslink density, swell ratio and bound rubber contents.

Nitrile rubber

Nitrile rubber is the generic name given to emulsion polymerized copolymers of acrylonitrile and butadiene. Its single most important property is exceptional resistance to attack by most oils and solvents. It also offers better gas impermeability, abrasion resistance, and thermal stability than the general purpose elastomers like natural rubber and SBR. These attributes arise from the highly polar character of acrylonitrite, the content of which determines the polymers particular balance of properties. NBR needed is generally based on oil resistance vs. low temperature performance. Nitrile rubber is used primarily in soling, plus hoses, tubing, linings, and seals used for the conveyance or retention of oils and solvents.[5]

15

Observations

After placing NBR round sample in toluene NBR swollen, hence mass increased.

Colorless toluene changed into blackish wine color.

After drying weight of NBR sample decreased from the original value.

Calculations

NBR is taken as sample, original weight = 1.26g

No. Time (hr) Weight(g) No. Time(hr) Weight(g)

1 3 1.74 7 24 2.083

2 24 2.259 8 24 2.131

3 24 2.261 9 24 2.105

4 24 2.105 10 24 2.117

5 24 2.206 11 24 2.111

6 24 2.136 12 24 2.110

Weight of NBR sample after drying in oven for 24 hr = 1.091g

Weight of NBR sample after atmosphere drying for 24 hr = 1.088g

0

0.5

1

1.5

2

2.5

0 24 48 72 96 120 144 168 192 216 240 264 288

We

igh

t (g

)

Time (hr)

Graph between swollen sample weight and time

16

References

1. Crol, S.G., Application of the FloryRehner equation and the Griffith fracture criterion to paint stripping. 2009.

2. RANI JOSEPH, K.E.G., D. JOSEPH FRANCIS and K. T. THOMAS, Polymer-Solvent Interaction Parameter for NR/SBR and NR/BR Blends. 1986.

3. Choi, S.-S., Difference in bound rubber formation of silica and carbon black with styrenebutadiene rubber. 2002: p. 466474.

4. Choi, S.-S., Effect of Bound Rubber on Characteristics of Highly Filled StyreneButadiene Rubber Compounds with Different Types of Carbon Black. 2004: p. 6.

5. Ciullo, P.A.H., N., The Rubber Formulary2008: Elsevier Science.

17

EXPERIMENT 6

Blending of Polypropylene and Ethylene propylene diene monomer in an internal batch mixer.

INGRIDIENTS FORMULATION

EPDM 60 PHR

PP 40 PHR

Silica 35 PHR

Sulfur 2 PHR

Dibenzthiazyal-disulfide MBTS 2 PHR

Tetramethylthiurum-disulfide TMTD 1 PHR

Anti-degradent 1 PHR

ZnO 1.5 PHR

Steric acid 1 PHR

Procedure

First of all to convert the formulation from Parts per Hundred PHR to grams multiply with the

factor 0.19 for easy calculations.

Weigh all the ingredients which are required for the blending of PolyPropylene and Ethylene

Propylene Diene Monomer Rubber.

Switch on the Internal Mixer and set its temperature up to 175oC and 50 RPM.

Take the weighted thermoplastic i.e. Polypropylene in internal batch mixer and mix it for almost

2 minutes.

Add Ethylene Propylene Diene Monomer Rubber and blend them for 2 minutes.

Incorporate silica and mix it for 2-3 minutes and give extra 5 minutes for the blending in chamber.

Mix all rest of the ingredients and add them into the blend, in the chamber of internal mixer and

mix the blend for 2 minutes.

After all this add sulfur and mix it for 1-2 minutes.

Homogenize it and take out the blend from the Chamber.

Observations and Theory

Ethylene Propylene Diene Monomer

An extensive range of EPDM polymers are produced by varying the molecular weight, molecular weight

distribution, ethylene/propylene ratio and level and type of diene termonomer. Elastomers are available

containing from 50% to more than 75% ethylene by weight. Polymers with lower ethylene content are

amorphous and easy to process. Higher ethylene content gives crystalline polymers with better physical

properties, but more difficulty in processing. The amount of terpolymer is typically 1.5 to 4%, but can be

as high as 11% in ultra-fast curing grades. Most EPDMs are incompatible with diene rubbers (eg. natural,

SBR, NBR) because of their relatively slow cure rate. The ultra-fast cure EPDMs overcome this.[1]

18

In general, the ethylene propylene rubbers are compounded to provide good low-temperature flexibility,

high tensile strength, high tear and abrasion resistance, excellent weatherability (ozone, water, and

oxidation resistance), good electrical properties, high compression set resistance, and high heat

resistance. The high molecular weight crystalline EPDMs can incorporate high levels of fillers. EPMs and

EPDMs have low resistance to hydrocarbon oils and their lack of building tack must be compensated for

by the use of resin.[1]

Polypropylene

Polypropylene is a semi-crystalline polymer known for its low density, and its somewhat higher stiffness

and strength than PE-HD. However, PP has a lower toughness than PE-HD. Polypropylene homopolymer

has a glass transition temperature -10oC, below this temperature it becomes brittle. However, when

copolymerized with ethylene it becomes tough. Because of its flexibility and the large range of properties,

including the ability to reinforce it with glass fiber, polypropylene is often used as a substitute for an

engineering thermoplastic. When injection molding the PP, the melt temperature should be between 250

to 270oC, and the mold temperature 40-100oC. Typical applications for injection molded polypropylene

parts are housings for domestic appliances, kitchen utensils, storage boxes with integrated hinges (living

hinges), toys, disposable syringes, food containers, etc

Blending process

There are five stages in the blending process. They are:

Put the Elastomers into the mixer chamber in which materials are to be mixed

Mixing is achieved by deforming the heat softened batch of feed by rotating blades

Incorporation of ingredients

Distribution

Dispersion

Observations

Blackish brown color

Soft when blend is removed from the mixer but gets very harder after few minutes

It does not give color upon touching its surface

Hard and rigid

No agglomeration of additive

Good distribution and dispersion

No blooming due to sulfur

No bubbles on the surface due to air snare

Degrade due to high temperature of internal batch mixer

References

1. Ciullo, P.A., Rubber Formulary1999.

19

EXPERIMENT 7

Test the mechanical properties of the given compounded polymer or elastomer by using Universal

testing machine UTM.

Procedure

The procedure for determining the mechanical properties is given below:

Take the specimen and measure the width and thickness of the specimen with the help of gauge

meter.

Switch on the Universal testing machine UTM and computer system attached with it.

Set the parameters of UTM i.e. thickness, width, speed, shear rate, crosshead position,

elongation, stress, maximum duration of the test and force etc.

Place the specimen in the grips of the testing machine, taking care to align the long axis of the

specimen.

Tighten the grips evenly and firmly to the degree necessary to prevent slippage of the specimen

during the test, but not to the point where the specimen would be crushed.

Start the machine and Record the load-extension curve of the specimen.

Plot the graph and determine the properties of specimen.

Experimental conditions

The conditions were used for the experiment are listed below:

Temperature: 23OC

Speed of testing: 50(2) 10 %mm/min

Strain rate at start of test: 1.5 mm/mm min

Sample

Type IV (semi rigid) polypropylene random copolymer is used as sample for testing mechanical properties.

Random copolymer polypropylene

Polypropylene random copolymers are a type of polypropylene in which the basic structure of the polymer

chain has been modified by the incorporation of a different monomer molecule. Ethylene is the most

common comonomer used. This causes changes to the physical properties of the PP. In comparison with

PP homopolymers, random copolymers exhibit improved optical properties (increased clarity and

decreased haze), improved impact resistance, increased flexibility, and a decreased melting point, which

also results in a lower heat-sealing temperature. At the same time they exhibit essentially the same

chemical resistance, water vapor barrier properties, and organoleptic properties (low taste and odor

contribution) as PP homopolymer. Random copolymer PPs were developed to combine improved clarity

20

and impact strength, and are used in blow molding, injection molding, and film and sheet extrusion

applications. They are used in food packaging, medical packaging, and consumer products. Random

copolymer PP is mainly used in film, blow molding, and injection molding applications where high clarity

is a requirement.

Specimen Dimensions

The conditions were used for the experiment are listed below:

Thickness(a): 3.19mm

Width(b): 6mm

Overall length:110mm

Gauge length: 30mm

Clamping length: 70mm

Universal Testing Machine

It is used to find the mechanical properties of the polymers. For example it finds tensile strength, stress

strain curve, yield point, and modulus etc.

Figure: Universal Testing Machine

The main parts of the machine are:

Load frame

Load cell

Cross head

Extensometers

21

Output device

Test fixtures: specimen holding jaws

Calculations

Observations

Break from starting point

Break rapidly

0

2

4

6

8

10

12

14

16

18

0 5 10 15 20 25 30 35 40 45 50

Stre

ss N

/mm

2

Strain

Stress-strain curve

22

EXPERIMENT 8

Design the formulation of following products on theoretical basis to get the desire properties

Rubber Hoses for hot water

Polyurethane shoe soles

Outer body of refrigerator

Utensils of Melamine

Procedure

First of all enlist the desire properties of the product.

Select the ingredients according to the properties.

Design the formulation to best properties with optimized cost.

Formulations

1. Rubber Hoses for hot water

2. Polyurethane shoe soles

INGRIDIENTS FORMULATION EPDM 100 PHR

Carbon black 25 PHR

Sulfur 1 PHR

Dibenzthiazyal-disulfide MBTS 1 PHR

Tetramethylthiurum-disulfide TMTD 1 PHR

Anti-degradent 1 PHR

ZnO 1 PHR

Steric acid 0.5 PHR

INGRIDIENTS FORMULATION PU 100 PHR

Silica 30 PHR

ZnO 2 PHR

Sulfur 1.5 PHR

Organo tin compound 1 PHR

Stearic acid 1 PHR

Antidegradent 1 PHR

Processing oil 5 PHR

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3. Outer body of refrigerator

40 parts by weight of an acrylonitrile-butadiene-styrene graft copolymer resin (g-ABS)

30% by weight of a monomer mixture comprising a cyanide vinyl compound

Aromatic vinyl compound to about 70% by weight of a rubber polymer

UV stablizer (bruggalin) 10 weight %

4. Utensils of Melamine

INGRIDIENTS FORMULATION Melamine formaldehyde resin 68-75 PHR

Alpha cellulose or pulp fiber 25-20 PHR

Benzoic acid or phthalic anhydride 0.2-2 PHR

Zinc sterate 1-3 PHR

Colorants 1-3 PHR