MORPHOLOGY AND GROWTH OF EXTENDED CHAIN CRYSTALS OF POLYETHYLENE.
RENSSELAER POLYTECHNIC INST TROY N Y DEPT OF CHEMISTRY
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The morphology and growth of extended chain crystals of polyethylene is discussed on the basis of optical and electron microscopy. The spherulitic habit is shown to be caused by nucleation of new lamellae on the 001 surface of lamellae, branching of lamellae on their growth face, and thickening of lamellae. Spherulite centers have been identified down to the primary lamella. Analysis of intersections of lamellae during crystallization allowed the identification of intermediate stages of crystal growth. Fracture surfaces parallel to the growth face and the 001 face are discussed. Ripple decoration by surface recrystallization is developed as a tool for fracture surface study. Kink bands are described as growth defects. Bending of lamellae is shown to go by slip parallel to the polymer chains. Ripple and drawn out fiber annealing is analyzed. All observations on extended chain crystals are used to propose a mechanism of extended chain crystal growth of polyethylene under elevated pressure. Author