Effect of molecular weight distribution on the structure and mechanical properties of ultradrawn,ultrahigh-molecular-weight polyethylene cast from solution. I. Thermoluminescence and NMR

Ultradrawing of ultrahigh-molecular-weight polyethylene (UHMW-PE) films produced by gelation/crystallization from solution was investigated using thermoluminescence (TL), DSC, and pulsed NMR. The TL from an x-irradiated UHMW-PE gel film is considerably affected by ultradrawing. The TL glow peak is correlated with the α_c dispersion of the crystalline phase in the UHMW-PE gel film. The TL integrated intensity is weak for folded-chain crystals but strong for extended-chain crystals. An extra higher TL peak, observed for samples drawn 150x, is related to the appearance of some highly extended tie-chains in the interfacial region in the process of ultradrawing. On the basis of the above observations, the effects of molecular weight distribution on the morphology of UHMW-PE gel film are examined. It is concluded that B-PE (Broad MWD) having a broader MWD has better drawability than N-PE; but at a given draw ratio, higher modulus and tensile strength are realized for N-PE (Narrow MWD).