Study of the structure and molecular mobility of crystalline polyethylene by the methods of photo-elasticity and torsion pendulum

Abstract

The authors have studied the temperature dependence of birefringence and the phase difference between stress and birefringence of PE films in a sinusoidal mechanical field. PE films with different degrees of crosslinkage and different degrees of extension were studied. It was found that the phase difference ϕ between stress σ and birefringence δn changes sign from positive to negative in the temperature region 40–70°C. The results are interpreted in terms of the biphasic PE model containing an amorphous phase with positive optical anisotropy and the crystalline phase with negative anisotropy.