STUDY ON THE CRYSTALLIZATION KINETICS OF PURE PET AND FILLED PET
Zhu Pingping and Ma Dezhu(Department of Applied Chemistry, The University of Science and Technology of China)
The isothermal crystallization kinetics of pure PET and filled PET have been studied by DSC. The results indicate that PET nucleates heterogeneously. These heterogeneities may be the remainders of catalytic system, occasional impurities, or various ingredients. Different types of heterogeneities become active at different temperature, so PET have different crystallization mechanism at different temperature. Specially, one of the crystallization parameters-Avrami exponent n is fractional, and the fractional value of n is not constant in the temperature range studied. Additive CaCO3 may active the originally present heterogeneities, cause the nucleation activation energy to decrease; The result that filled PET has lower fold-surface free energy σe indicate that the chain diffusion activation energy decrease after CaCO3 is added to PET. Lower values of nucleation activation energy and chain diffusion activation energy means the dependence of the rate of crystallization on temperature decreased. The secondary nucleation is presented during crystallization of filled PET.