Styrene-butadiene rubber network structure

A gel made of a thermoplastic styrene-butadiene rubber (SBR) to which asphalt is added is also reported to be a shape memory material [8]. A small amoimt of SBR forms 3D networks in which a large amount of asphalt forms a phase separated structure (both components form co-continuous phase). When this gel is deformed at a low temperature, the plastic deformation of asphalt, which is much harder than SBR, dominates... 

It has already been pointed out in Chapter 13, Section Al, that maxima in the loss compliance and the retardation spectrum are characteristic of network structures as predicted from the Rouse theory, suitably modified, in Fig. 10-7. Such maxima appear in moderately cross-linked polymers as well as in uncross-linked polymers of high molecular weight, and their shapes are remarkably similar. In Fig. 14-3, J" is compared for styrene-butadiene copolymer without cross-links and cross-linked to a value of Gg = 7.3 X 10 dynes/cm, characteristic of a well-vulcanized soft rubber e.g., curve VI of Figs. 2-1 to 2-8). The curves are both close in shape to that predicted by the Rouse-Mooney theory for a most probable distribution of network strands, i.e., curve D of Fig. 10-7, as already evident from Fig. 13-1. 

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