Morphology and crystal growth rate of polyethylene crystalline complexes

An investigation of the morphology of crystallization of fractionated linear polyethylene has shown that single crystal platelets may be obtained from dilute xylene solutions only in a limited region of temperature. The variation of this temperature region with molecular weight is greater than would be expected from the theoretical variation in equilibrium melting temperature. Uniformity of the crystallization conditions was sufficient to permit the measurement of size and thickness of the crystals as a function of both time and temperature. It was shown that the change in platelet thickness with temperature cannot be accounted from by the kinetics of nucleation with the assumption that the thickness is essentially equal to the critical nucleus dimension. The crystal growth rate data show that growth occurs by a nucleation process but the data are not compatible with the assumption that nucleation occurs through the formation of a homogeneous monomolecular layer on the growth surface. Evidence is presented to show that crystallization habit is dependent not only on the degree of supercooling but is also a function of some other factor that acts as a resistance or impedance to crystallization.