| Summary: | The study was directed to develop a method to predict the influence of the rate of cooling to the degree of crystallinity (DOC) and volume change of crystalline polymers. Crystalline polymer melts exhibit volume shrinkage on cooling below melting point due to crystallization. Crystallization and volume shrinkage will proceed with varies rate as long as the temperature is above the glass transition temperature. DOC achieved by polymer is not only determined by the inherent crystallinity of the polymer but also influenced by the rate of cooling. On fast cooling, inherently crystalline polymer may have zero DOC. This incompletely crystallized polymer will crystallize and experience volume shrinkages on prolong usage at temperatures above glass transition temperature. A mathematical model and a kinetic model of crystallization based of modification of Avrami equation were solved simultaneously to give temperature and DOC distributions as functions of time for various rate of cooling. Rate of cooling was varied by changing the water bath temperature. Laboratory measurement was done to verb the predicted temperature profile and average degree of crystallinity. The simulated temperature profiles as well as average degree of crystallinities give good agreements with experimental results.
Keywords: polymer, degree of crystallinity, cooling, melting point, crystallization, volume shrinkage, molding
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