2 homopolymers Elastomers, reinforcement with

Impact-resistant properties, especially at low temperatures, low-temperature toughness, melt-processing properties, and dimensional stability of thermoplastic polyurethane elastomers are improved by the addition of a carbonyl-modified polyolefin [54,55]. These improvements are particularly useful for reinforced polyurethanes. Small amounts of polyolefin homopolymer or copolymer with TPU blends are useful for molding plastic articles by injection molding, extrusion, calendering, or similar process for molding thermoplastic articles [56]. 

This year s U.S. production of thermoplastics, thermosets, and synthetic rubber is expected to be 29 billion pounds. About 80% of this is based on only a few common monomers. To improve performance, the polymer industry rarely changes to a new, probably more expensive polymer, but instead it shifts from mere homopolymers to copolymers, polyblends, or composites. These three types of multicomponent polymer systems are closely inter-related. They are intended to toughen brittle polymers with elastomers, to reinforce rubbers with active fillers, or to strengthen or stiffen plastics with fibers or minerals. 

As with all other IPN s the modulus becomes roughly constant (actually following G = bRT) at temperatures beyond the glass transition zone. This of course is a result of both components being crosslinked. Above ca. 125 C. these materials behave as ordinary non-reinforced elastomers. The actual modulus in the rubbery plateau region ca. 4 x 10 dynes/cm was roughly the same for homopolymers and IPN s. 

PC is more resistant to strong acids but is less stable than polyterephthalates (PET, PBT) to benzene and methanol. PET, polyethylene terephthalate, is a hard, stiff homopolymer, whilst PBT, polybutylene terephthalate is somewhat softer. Further materials in this group include, i) thermoplastic poly (ether) ester elastomers, included in the TPE grouping, ii) amorphous polyarylates, and Hi) self-reinforced crystalline polyarylates (LCP). Polycarbonate may be blended with various styrenics (PC/ABS, PC/ASA, PC/SMA). 

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