Glassy polymers elastomeric networks

The crosslinks in an elastomeric network can also be temporary or physical aggregates, for example, the small crystaUites in a partially crystalline polymer or the glassy domains in a mulhphase triblock copolymer [3,7]. Addihonal informahon on the crosslinking of chains has been provided in the following sechons. 

Similar inhomogeneities, also attributable to local variations in crosslink density and the consequential network flaws, were observed in non-elastomeric networks in the glassy state. Some of these observations date from as early as the late 1950s [722, 723]. Although several families of polymers exhibited these inhomogeneities, they appear to have one common denominator they are all... 

Enhancement of impact toughness in some semicrystalline polymers is similar to techniques used for some glassy polymers. Usually an elastomeric phase is melt-blended into the host polymer, resulting in a dispersion of spheroidal elastomeric particles or a network. Compatibilization is obtained by copolymerization or chemical reaction at the interface. The toughening mechanisms may include both massive crazing and cavitation-plastic deformation, depending on the... 

In any case, if this polymerized form of elemental sulfur is quenched (cooled rapidly), it becomes a solid. This solid is glassy at very low temperatures, but becomes highly elastomeric above its glass-transition temperature of approximately -30 °c.6 8 14 30 The situation is complicated by the presence of unpolymerized S8 molecules which would certainly act as plasticizers. So far, attempts to cross-link the elastomeric form into a network structure suitable for stress-strain measurements have not been successful. The polymer is unstable at room temperature, gradually crystallizing, and eventually reverting entirely to the S8 cyclics. 

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