CRYSTALLINITY INCREASES IN SEMI CRYSTALLINE POLYMERS DURING HIGH-RATETESTING

During low rate deformation in tension semi-crystalline polymers can u ndergo a strain induced crystallisation during deformation which leads to increases in now stress. This work extends studies of crystallinit y in the polymers PEK, PEEK and PET to compression at high strain rate s at a variety of temperatures. All three polymers show large increase s in crystallinity when tested at high rates with PEK and PEEK shelvin g increases only at rates of 10(3)/s. It is speculated that the rapid increases in now stress reported in polymers at high strain rates may be due to the rapidity of strain induced crystallisation at these stra in rates.