SynopsisExperiments have been conducted to examine the effect of the following agents: TiOz, CaO, MgO, BaS04, SiOz, and A1203 as modifiers on the poly(ethy1ene terephthalate) crystallization kinetics. Modifier concentration in the polymer varied from 0.5% to 3%. Crystallization rate measurements at a temperature of 237OC were performed by dilatometric method and measurements of spherulitic growth rate, by microscopic method. It has been stated that the addition of a modifier affects the crystallization rate, dimension, and homogeneity of spherulitic sizes. The spherulitic growth rate, with the exception of that modified by CaO, does not depend on the kind and the concentration of a modifier. Heterogeneous nucleating agents exert an effect, then, mainly on the heterogeneous nucleation process. In the presence of the agents, the nucleation in the poly(ethy1ene terephthalate) is of athermal character. The kind of a modifier applied exerts also an effect on the final crystallization degree.

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SynopsisThe dependence of the fold period in poly(ethy1ene terephthalate) (PET) crystals on overcooling was investigated by the small-angle x-ray diffraction met,hod, for samples crystallized at 150' to 260°C. The equilibrium melting point T,, determined simultaneously, was 278" f 2°C. Using t,hese results, the surface free energy ue was calculated.

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