Pattern Formation in Polymer Solidification

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The kinetics of crystallization are, in general, controlled by two competitive phenomena, the thermodynamic driving force, which forces the crystal/noncrystal interface forward, and the rate at which the heat of fusion and any unincorporable components can flow away from that interface. Over a wide range of conditions, this competition causes the interface to assume intricate patterns. The aim of the proposed work is to develop an experimental base and a theoretical framework by which such pattern formation in polymer systems can be understood. This work will be directed at spherulitic crystallization in polymer blends and at the development of microstructure in melt-spun fibers. An experimental program for quiescent crystallization will be carried out. In this, both constrained (by forced movement through a temperature gradient) and unconstrained spherulite-like growth will be studied. In both cases, microstructural parameters will be measured and compared to model predictions. Likewise, a study will be made of the temperature and crystallite radius of oriented polymer fibers crystallized by running them through a temperature gradient. These will be compared to those of a model developed by the principal investigator. It is expected that the work will also extend existing theory for pattern development in polymers.