Influence of the Antimony Catalyst Remnants On the Melt Crystallization of PET

The nucleating activity of antimony catalyst remnants on the melt crystallization of poly (ethylene terephthalate) (PET) is proved through comparisons, for samples with Sb concentrations in the range 180-1850 ppm, of the crystallization behaviors before and after a complete extraction of the catalyst remnants. These comparisons are performed by analysis of the crystallization peaks of differential scanning calorimetry (DSC), by the study of isothermal crystallization kinetics from X-ray diffraction experiments, and by optical microscopy observations of the size of the spherulites. The dependence of the crystallization temperature (T(c), as evaluated by the position of the DSC peak) on the Sb concentration, reported in the literature, is shown to be largely overestimated. In particular, it is found that the T(c) of commercial samples are essentially unaffected by the presence of the standard concentrations of Sb catalyst remnants.