Effect of Strain-Induced Crystallization on the Elastomeric Properties of cis-1,4-Polybutadiene Networks

TLDR: In this paper, the authors show that polymer networks, when studied at very high elongations, show anomalous stress-strain isotherms in that they exhibit values of the modulus or reduced force which increase markedly with increasing elongation.

Abstract: Polymer networks, when studied at very high elongations, frequency show anomalous stress-strain isotherms in that they exhibit values of the modulus or “reduced force” [ƒ*] which increase markedly with increasing elongation. Such isotherms depart appreciably from the form predicted by the molecular theories of rubberlike elasticity and from the Mooney—Rivlin representation adopted from phenomenological arguments as well. For this reason, the interpretation of the increase in [ƒ*] at high elongations has been of great interest for a considerable period of time. For several decades now, this behavior has generally been attributed to the limited extensibility of the network chains. Critical examination of various published results pertinent to this question, in conjunction with more definitive experimental studies reported recently, however, support the alternative suggestion that such atypical isotherms are due to strain-induced crystallization. One experiment particularly relevant to this issue is...