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Abstract

A comparative study of the stress induced crystallization of natural (Hevea, Guayule) and synthetic high cis-1,4-polyisoprenes at room temperature is presented. Hevea and Guayule are both found using WAXS to crystallize into the unit cell of Morss and Bunn previously described for Hevea. DSC studies of polyisoprenes held at −25°C indicate that Hevea and Guayule crystallize more rapidly than synthetics. Studies of relative birefringence and stress decay following uniaxial extension confirm this. Under conditions of comparison at the same stress, raw Hevea crystallizes more rapidly than extracted Hevea, Guayule, and the other polyisoprenes.