Kinetics of strain‐induced crystallization of a <i>trans</i>‐polypentenamer

Abstract

Abstract The kinetics of the strain‐induced crystallization of a crosslinked 89% trans ‐polypentenamer was studied as a function of temperature and strain by using a combined birefringence—stress relaxation technique. The crystallization rate was found to be extremely sensitive to both variables and was, within experimental error, a function of the degree of undercooling alone, the increase in crystallization rate with strain being a direct consequence of the melting point elevation. From the isothermal, isometric crystallization rates, the development of crystallinity in constant‐rate‐of‐strain experiments was calculated and related to characteristics of the stress‐‐strain curve and of the temperature‐strain rate dependence of tensile strength. These calculations allow one to estimate under what conditions sufficient crystallinity may be expected for the attainment of high strength in absence of reinforcing fillers. Crystallinities measured in this work were of the order of 10% or less. A limited x‐ray diffraction study confirmed the low order of crystallinity indicated by the stress‐birefringence measurements. The relatively high precision of the latter makes this technique attractive for the estimation of small straininduced crystallinities in rubbers.