Elastomers, thermoplastic segmented copolymers

Block copolymers were developed rapidly in the 1960s when living anionic polymerization was first utilized to synthesize triblock thermoplastic elastomers or elastoplastics. At the same time, step or condensation polymerization to produce thermoplastic polyurethanes, urea-urethane spandex fibers, and later more specialized materials, such as the semicrystalline polyester-polyether copolymers were developed [10]. Imide block or segmented copolymers utilizing... 

Olefinic thermoplastic elastomers are block copolymers or blends of polyolefins — commonly, polypropylene, which forms the hard crystalline block, and another olefin block, most commonly ethylene or EPDM. Some less common soft segments include natural rubber, nitrile rubber, and EVA. Olefinic thermoplastic elastomers exhibit better processability than neoprene and have excellent resistance to oils. Therefore, they offer attractive replacements for neoprene in oil-resistant wire and cable insulation. 

There are two important types of polymer in which an elastomeric and a glassy or non-crystalline rigid component are copolymerised. The simpler thermoplastic elastomers are usually triblock ABA copolymers with B as the elastomeric component and A as the glassy component, whereas the segmented polyurethane elastomers are multiblock copolymers in which alternate blocks are hard , i.e. relatively inflexible, and soft , i.e. relatively flexible. 

Thermoplastic polyolefin (TPO) elastomers are typically composed of ethylene propylene rubber (EPR) or ethylene propylene diene M (EPDM) as the elastomeric segment and polypropylene thermoplastic segment. LDPE, HDPE, and LLDPE copolymers ethylene vinyl acetate (EVA), ethylene ethylacrylate (EEA), ethylene, methyl-acrylate (EMA) and polybutene-1 can be used in TPOs. Hydrogenation of polyisoprene can yield ethylene propylene copolymers, and hydrogenation of 1,4- and 1,2-stereoisomers of S-B-S yields ethylene butylene copolymers. ... 

Styrenic block copolymers and their compounds have been in widespread commercial use for many years, with many applications. With the latest technology, they have become particularly interesting as impact modifiers for plastics, both thermoplastics and thermosets. Most polymers are thermodynamically incompatible with others polymers and mixtures tend to separate into two phases, even when they are part of the same molecule, as in block copolymers. Poly(styrene-P-elastomer-P-styrene) copolymers, in which the elastomer is the main constituent, give a structure in which the polystyrene end-segments form separate spherical regions ( domains ) dispersed in a continuous phase. 

Thermoplastic copolyester elastomers are multiblock copolymers built up from so-called short crystallizable hard segments and long flexible segments. Owing to such chemical structure, TPEEs exhibit unusual combination of thermoplastic and elastomeric behavior. Physical and mechanical properties of these copolymers strongly depend on the chemical composition and the molecular structure... 

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