Elastomers, single most important

Reversible network structure is the single most important characteristic of a thermoplastic elastomer. This novel property generally arises from the presence of a phase-separated morphology in the bulk material which in turn is dictated by the molecular structure, often of a block copolymer nature. A wide variety of synthetic methods can, in principle, produce endless varieties of thermoplastic elastomers this fact coupled with the advantageous processing characteristics of these materials suggest that the use of thermoplastic elastomers will continue to grow in the 1980 s. 

The equation of state for rubber elasticity, embodied by any of equations (6-53) through (6-60), is important not only because it is historically the first quantitative treatment of molecular theories for elastomers but also because it laid a conceptual foundation for theories for the physical properties of polymers in general. Some of these have been discussed in detail in previous chapters. Perhaps the single most significant contribution is its recognition of the role of... 

The most important commercial use of elastomer blends is in the huge tire market. These blends are generally phase separated and represent one of the largest single applications for immiscible or miscible blends. Ckjmpatibilization is achieved via crosslinking reactions across the interface. The use of SBR/PB (polybutadiene) and NR(natural rubber)/PB for tread, NR/SBR/PB and NR/PB for carcass, NR/PB and NR/SBR for sidewall and NR/SBR/PIB... 

Block copolymers are an important class of polymers used in many applications from thermoplastic elastomers to polymer-blend stabilizers. Their synthesis is most often done by ionic polymerization, which is both costly and sometimes difficult to control. However, block copolymer properties strongly depend, for example, on the exact chemical composition, block molar mass, and block yield. These parameters can be evaluated in a single experiment using copolymer GPC with multiple detection. 

Impact strength is usually only determined for plastics and hard elastomer compounds (i.e., those in the D durometer hardness range), where the impact resistance of the material in actual service is important. Soft elastomer compounds will bend, not break, on impact unless they have been cooled below their brittleness temperature. Several types of impact testers and test methods are available. Basically, they all measure the energy required to break a test specimen in a single sharp blow, and can be performed over a temperature range from -70 to +120°C (-94 to +248°F). The most widely used tests are Izod Impact and Charpy Impact both procedures are given in ASTM D-256. 

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