| Abstract: | The solution crystallization kinetics and crystal dissolution behavior of three grades of poly (ethylene terephthalate) in N-methyl–2-pyrrolidinone were studied were using turbidimetric and calorimetric methods. The influence of concentration on the equilibrium dissolution temperature was described using Flory's melting point-composition relationship. The effect of the solvent alkyl group was also investigated. N-ethyl-2-pyrrolidinone was found to be a better solvent than N-ethyl–2-pyrrolidinone or N-cyclohexyl–2-pyrrolidinone for poly (ethylene terephthalate). From the calorimetric experiments, it was determined that two crystallization processes (primary and secondary crystallization) were responsible for the total crystallinity. The primary process dominated the early stages of the crystallization process and accounted for the majority of the final crystallinity for lower polymer concentrations. Based on coherent secondary nucleation theory, the effect of the crystallization temperature on the primary crystallization rate constant was quantified in terms of a temperature coefficient. This temperature coefficient was found to be relatively insensitive to PET concentration, PET structural impurities, and solvent alkyl group. © 1993 John Wiley & Sons, Inc. |
