1.Elastromers (Rubbers)Submitted by: Samyak Suyal Roll no. : R820211030

2. What are Elastomers An elastomer is a polymer with visco-elasticity (colloquially "elasticity"), generally having low Youngs modulus and high failure strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber. Elastomers are amorphous polymers existing above their Glass Transition Temperature, so that considerable segmental motion is possible. 3. Types of Elastomers Thermosets ThermoplasticNote: Elastomers are usually Thermosets (requiring vulcanizaton) but may also be Thermoplastic. Thermosetting polymer as a pre-polymer in a soft solid or viscous state that changes irreversibly into an infusible, insoluble polymer network by curing. Curing can be induced by the action of heat or suitable radiation, or both. A cured thermosetting polymer is called a thermoset. A thermoplastic, or thermosoftening plastic, is a polymer that becomes pliable or moldable above a specific temperature, and returns to a solid state upon cooling. Most thermoplastics have a high molecular weight. 4. Common characteristics; Large elastic elongation (i.e.200%) Can be stretched and then immediately return to their original length when the load was released Elastomers are sometimes called rubber orrubbery materials The term elastomer is often used interchangeably with the term rubberIdealized stress-strain curves for metals, conventional plastics and elastomer 5. Elastomeric Materials No StressStressed In tension 6. Natural Rubber Creep Solved by Goodyear in the 1800's Discovered that the polymer could be crosslinked(cured or vulcanized) by heating with sulphurSynthetic Polyisoprene or Isoprene Rubber Need Used in tires for bicycles and early cars. Used the Ziegler-Natta catalyst system to improve properties. The trans- or cis- nature of the rubber could be controlled up to 90% in either direction. 7. Butadiene Rubber (BR) No cis or trans isomers. Lower mechanical strength because of no ofpendant methyl group but also more flexibility. Lower cost (all synthetic from cheap monomer) Improvement of low-temp flexibility. Compatibility with other polymer materials. H CH HC CH HC HH 8. Oil-Resistant Elastomers NBRNitrile Butadiene Rubber Copolymerization of butadiene and acrylonitrile More expensive than SBR or BR CRChloroprene rubber (neoprene) Thermal stability Non-flammable 9. Thermoplastic Elastomers (EPM and EPDM) Many of the properties of thermosetelastomers Resiliency Elasticity More easily processed Injection molding, extrusion and other standard thermoplastic processes. Highly compatible with polyolefins. EPDM is crosslinked very lightly and may not be capable of being melted. 10. Thermoplastic Olefin Elastomers (TP Block tripolymers (such as SBS) with hard andsoft domains. Poor compatibility with other rubbers. Melt processible.Flouroelastomer sMany of the desirable properties offlouropolymers Low solvent effects -Excellent for chemical and petroleum handling applications High thermal stability -Good for gaskets and seals 11. Flouroelastomers HFH CF CCCF Tetrafluoroethylene monomerH F Vinylidene fluoride monomerFHSiliconesHHHSHCOCHHH 12. THANK YOU