Experimental Results on the Relationship between Tensile Strength and Network Structure

Experimental Results on the Relationship between Tensile Strength and Network Structure.—The tensile strengths of a series of vulcanized butyl rubber polymers differing solely in primary molecular 

When the butyl rubber was compounded with up to 30 percent of polyisobutylene, which, lacking the unsaturated isoprene units, did not enter into the cross-linking reaction, the tensile strengths were, of course, considerably reduced. They were found nevertheless to be accurately represented by the same equation, (53), provided merely that Sa is taken as the fraction of the composite specimen consisting of network chains subject to orientation. Thus, in this case 

The decrease in tensile strength with over-vulcanization by con- 

We have called attention previously to the fact that by no means all of the chains of a network are lengthened, in the sense that their ends are moved farther apart, by elongation of the sample those with displacement vectors situated transverse to the axis of elongation are shortened. The proportion of the chains which are lengthened by a macroscopic elongation a of the sample can be shown to be given by 

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