Loss Compliance and Retardation Spectrum

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. 

Loss shear compliance (reduced to 2S C) of styrene-butadiene rubber, uncross-linked (t/) and cross-linkeiP with log Jg = —6.86s (O- 

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