4. THERMOPLASTIC ELASTOMERS
Thermoplastic Elastomers result from copolymerization of two or more
monomers.
• One monomer is used to provide the hard, crystalline features, whereas the
other monomer produces the soft, amorphous features.
• Combined these form a thermoplastic material that exhibits properties similar
to the hard, vulcanized elastomers.
TPEs (thermoplastic elastomers) have the properties and performance of
rubber, but are processed like plastic.
TPEs are flexible materials that can be repeatedly stretched to at least twice
their original length at room temperature and return to the approximate length of
the original shape upon stress release.
7. Properties
Dense rubber
Slip resistance
Excellent weather resistance
Shock absorption
Outstanding ozone resistance
Flexibility
Soft texture
Benefit of being co-extruded
UL and NSF approval with certain TPE grades
Advantages
Simplified processing - no mixing or vulcanization involved
Lower part costs through lower density and thinner wall sections
TPEs are colorable
Recyclable scraps and parts
Long-lasting
Markets utilizing these materials
HVAC
Appliances
Automotive
8. Styrene
Styrene, also known as ethenylbenzene, vinylbenzene, and phenylethene, is
an organic compound with the chemical formula C6H5CH=CH2.
9. 1,3-Butadiene is the organic compound with the formula (CH2=CH)2. It is a
colorless gas that is easily condensed to a liquid. It is important industrially as
a monomer in the production of synthetic rubber.
Butadiene
10. Styrene-butadiene rubber (SBR)
• Developed during World War II
• Germany under the name of BUNA-S.
• North America as GR-S, Government rubber-styrene.
• Random copolymer of butadiene (67-85%) and styrene (15-33%)
• Not capable of crystallizing under strain and thus requires reinforcing filler,
carbon black, to get good properties.
• One of the least expensive rubbers and generally processes easily.
• Inferior to natural rubber in mechanical properties
• Superior to natural rubber in wear, heat aging, ozone resistance, and
resistance to oils.
• Applications include tires, footwear, wire, cable insulation, industrial rubber
products, adhesives, paints (latex or emulsion)
• More than half of the world’s synthetic rubber is SBR
• World usage of SBR equals natural rubber
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15. SBR by Solution Polymerization
• It obtain by anionic polymerization of styrene and butadiene.
• Initiator is lithium alkyls in paraffin or cycloaliphatic solvent
• Purification of solvent and monomer is required
• Dry nitrogen blanketing I also required.
• Dry solvent like n-hexane or cyclopentane is used.
• Styrene, butadiene and initiator are added batch wise in
reactor depending on grades to be produced
• In end of the reaction chain ends are terminated by addition of
substances which control the property of polymer
16. • Unreacted monomer and flash vaporized with some portion of solvent
and condensed and recycled in wet solvent tank.
• Concentrated polymer solution is blends in the blends tank.
• Than some antioxidants agent is fed in stripping section, where the
solvent is removed by steam distillation in presence of a dispersing
agent aimed to control the crumb size in slurry.
• The crumb slurry is sent for dewatered on shaker screen and than
dried and cooled with air.
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18. SBR by Emulsion Polymerization
The production of SBR follows addition polymerization.
SBR is produce by the copolymerization of butadien and styrene by emulsion
polymerization in 3:1 weight ratio.
The fresh and recycle monomers are purifiedby20%aqueous caustic
purification.
Then the stream is continuously passed or SSR.The reaction time in these
reactors ranges from 5 to 15hr.
Appying all steam heating, cooling a and other.Tgese reactors are producing
both hot and cold SBR.
After the completion of the polymerization the latex resulting from the reactors
are collecting in blow down tanks.
This removed a butadiene and bottoms are fed to a perforated plate collumn
were styrene is stripped out.
The monomer free emulsion is then added with certain compounding
ingradients in blend thanks.
The latex is coagulated to rubber.
19. The crumbs of rubber float onto shaker screens where the catalyst, emulsifier
and other solubles are removed by the action with wash water.
The crumbs are dried in continuous belt dryers with hot air and are
subsequently pressed into bales.
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21. Properties of SBR
• SBR is general purpose rubber. It excels most grades of natural rubber in
uniformity and cleanliness
• It’s permeability , heat resistant to wear and aging is superior to natural
rubber.
• It is inferior in workability , tensile strength, tear resistance, cut growth and
heat build up.
• SBR requires more severe milling than natural rubber, however over milling
causes a considerable decrease in the tensile strength. Large amount of
plasticizer and softener are also required.
• SBR may be vulcanized with vulcanizing agent without sulfur like diazo
derivatives, quinines etc. The vulcanization rate in the case of SBR product is
lower than that for natural rubber.
• Special Carbon black had been developed for reinforcing SBR.
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26. Applications of SBR
• SBR Major use for production of pneumatic tires of light duty vehicle.
• SBR is also used in cables, mechanical goods , footwear and shoes, formed
items, belts, hoses, tubing, sponge, coated fabrics, flooring and adhesive.
• It also used by speaker driver manufacturers as the material for Low Damping
Rubber surrounds.
• SBR is often used as part of cement based structure waterproofing system.
• SBR rubber pads (Mining equipment).
• Synthetic Rubber Seals.
• Rubber gaskets.
• SBR Panel grommets (HVAC market).
• Custom molded rubber components for plumbing applications.
