6533b85efe1ef96bd12c066a

RESEARCH PRODUCT

A quantitative electron microscopic study of the crystallite structure of molecular weight fractions of linear polyethylene

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Utilizing thin-section techniques, transmission electron microscope studies were performed on a series of bulk-crystalized fractions of linear polyethylene covering the range M = 5 × 103−6 × 106. The crystallization conditions were varied from long-time isothermal to rapid quenching. Quantitative analysis could be carried out on such samples crystallized under controlled conditions. The crystallite thickness distributions and long periods are presented in terms of histograms. From these data the degree of crystallinity can be calculated and was found to compare favorably with that from other methods. The amorphous thickness increases significantly with molecular weight for all modes of crystallization. On the other hand, the crystallite thickness is essentially independent of molecular weight for very rapid crystallization, and shows a complex dependence on chain length for isothermal crystallization. The tilt angle, the angle of inclination of the chain axis with the lamellar basal plane, has also been determined. There is a tendency for this angle to increase with decreasing crystallization temperature. This observation can be related to the crystallization mechanisms.