抄録
Crystalline polymers show non-linear viscoelastic properties at very low excitations compared with amorphous polymers. It is very difficult to discuss the non-linear viscoelasticity generally, However, the degree of non-linearity has been defined at the temperature region where the dispersion due to crystal is important, as a result of considerations based on simple mechanical model and phenomenological method. The temperature dependency of this degree of non-linearity has been examined by making experiments of stress relaxation for high and low density polyethylenes and polyethylenet erephthalate. The result is that the degree of non-linearity is related to the dispersions closely, that is, the degree of non-linearity has larger values at the starting points of each dispersion. These facts suggest that the interaction between different dispersions will be the main factor for the non-linear viscoelastic mechanism.
