Ductile–brittle transition in polymers

Tensile experiments on polypropylene and various rubber‐modified polypropylenes, conducted over a wide range of temperatures and strain rates, have shown that the ductile–brittle transition in these highly crystalline polymers is strongly affected by both temperature and strain rate. Such polymers can either craze or shear yield, depending on the temperature and rate of test. High temperatures and low strain rates favor shear yielding, while low temperatures and high strain rates promote crazing. The ductile–brittle transition of these polymers may be understood as due to an alteration in deformation mode, as proposed by Matsushige et al. The competition between crazing and shear yielding dictates the subsequent failure mode. The dependence of the ductile–brittle transition on the test and material parameters (such as temperature, strain rate, pressure, orientation, notching, and plasticizer) may be ascribed to the respective influences of these parameters on crazing relative to shear yielding.