Observations of Deformation in Spherulitic Polyethylene

A thin film marker technique is described for determining quantitatively from replicas the nonhomogeneous deformation modes operative in spherulitic polyethylene. Experiments were conducted at temperatures from −20° to 120°C and strain rates of the order of 0.04 sec−1. At −20°C, pronounced deformation at spherulite boundaries is observed. This results in stress concentrations which cause the accompanying nonhomogeneous deformation of the spherulites themselves to occur. At 70°C, corresponding to the α relaxation, the deformation has become almost entirely homogeneous within lamellae. At 120°C, corresponding to the α′ relaxation, lamellar boundary slip is clearly observed in addition to homogeneous deformation.