Polymer Crystallization: Polycarbonate and Polybutene-1

218 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.The crystallization of polycarbonate from the glassy state was examined using thin ($\sim$1000A), solution cast films and thicker (0.16 and 1.5 mm) compression molded films. A detailed study of the crystallization process in the thin films, as observed by transmission electron microscopy, revealed that spherulites grew by a nucleation and growth process; no evidence of nodular aggregation or enhanced nucleation by nodules was seen. The growth rates of the spherulites as a function of temperature, measured by a repeat replica process, were found to fit the Hoffman-Lauritzen kinetic crystallization theory. Differential scanning calorimetry (DSC) studies in the thicker films revealed that crystallization, after an initial induction period, increased in rate with increasing temperature and decreasing molecular weight. A double melting peak, in the range of 210-235$\sp\circ$C was also found by DSC, this behavior was attributed to two populations of crystals differing in size and/or perfection, which could not be explained in terms of degradation or surface effects.Crystallization of polybutene-1 from solution is known to exhibit polymorphism, with the resultant crystal structure depending on maximum solution temperature. No evidence for helical conformation in solution, which has been proposed to be the origin of this behavior, was found using intrinsic viscosity and nuclear magnetic resonance. It was found that at high crystallization temperatures (62$\sp\circ$C) and concentrated solution, that the solution history effects are greatly reduced. Therefore, the solution history effects may be better explained by the temperature of nucleation, or the rate of cooling from elevated temperature, rather than the helical conformations.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD