Abstract
The shear tests for amorphous polymers, (polyethylene terephthalate) (PET) and polycarbonate(PC) are performed under various conditions of strain rates and temperatures below the glass transition. Diffuse slip line(DSL) yield mode in which amorphous polymers deform plastically without a macroscopic shear band and necking has been observed under the conditions of relatively higher temperature and lower strain rate. The dependence of yield mode of PET and PC on the temperature and the strain rate is shown on a common yield mode map drawn with temperature difference from their glass transition temperatures, which suggests strongly that mobility of segment chains under the mechanical stress should be responsible for the generation and growth of diffuse slip lines. The growth rate of the diffuse slip line is given by the rate process theory, and the activation energy and the activation volume are estimated to be 240 kJ/mol and 3.1 nm3 for PET, and 110 kJ/mol and 5.3 nm3 for PC.
