ENERGY EQUATION AND THE CRYSTALLIZATION KINETICS OF SEMICRYSTALLINE POLYMERS - REGIMES OF COUPLING

The processing conditions play an important role in the development of the crystallinity of thermoplastic polymers and the energy equation d escribing the heat transfer problem can be strongly coupled to the mat erial kinetics. In this paper, the importance and nature of the coupli ng is evaluated by comparing the temperature and crystallinity distrib utions obtained from a fully coupled zone model (considered as the mos t general approach) with two cases: Neumann's solution (sharp interfac e-moving boundary) and the one-domain diffusion equation with no heat generation (uncoupled solution). Two non-dimensional parameters, Stefa n's (St) and Deborah's (De) numbers, that play a key role in determini ng the extent of the coupling, are isolated. The influence of the coup ling and its nature have been demonstrated numerically in selected cas es. Results of the parametric studies show that De and St decide the n ature of the coupling. The error made by decoupling the problem can be shown graphically and regimes are identified where the coupling is im portant or negligible. Criteria allowing the identification of the reg imes are presented. Finally, an example is presented to demonstrate th e importance of the coupling for the cooling of Nylon 6-6 and PET, whi ch exhibit fast and slow crystallization kinetics.