Lamellar deformation and its variation in drawn isolated polyethylene spherulites

Observations of individual lamellae within spherulites of linear polyethylene, drawn under affine conditions between room temperature and ∼100 °C, show lamellae surviving to sample failure, thereby providing a strong memory of the initial morphology in the final product. Lamellae rotate and deform according to the angle their plane makes with the draw direction. Those parallel to the draw direction extend, to the full draw ratio, by shear in the basal plane, probably in {110} planes and at constant lamellar thickness. The same mechanism appears to occur for lamellae at higher angles with chain slip expected increasingly to operate. This latter mechanism is responsible for lamellar thinning, which becomes universal in elongated lamellae at higher draw ratios. Lamellae whose planes are transverse to the draw direction contract, with kinking—also by chain slip—to produce bands of sheared lamellae in spherulite centres. The temperature of drawing has little pronounced effect on the drawn morphology unlike draw rate whose influence is evident. Faster draw produces more severe local damage and less-well-organized co-operative kinking. The amelioration of these effects at a slower rate is attributed to molecular mobility and the influence of the surrounding molecular network.