Crystallization behavior of syndiotactic and atactic 1,2-polybutadiene blends

Two 1,2-polybutadiene samples, ie syndiotactic 1,2-polybutadiene (sPB) and atactic 1,2-polybutadiene (aPB), were synthesized by using the same Iron (III) catalyst system, although with changing 14 contents of the third catalyst component. Effects of the composition of aPB on the crystallization behavior of sPB have been characterized by wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Analysis of the results indicates that the intensity of the (010) peak of sPB is influenced much more easily than that of the (200)/(110) peak by the amorphous aPB sample, but the structure of sPB does not change with the changing composition of sPB. aPB is thermodynamically miscible with sPB in the melt, and retards the melt crystallization of sPB. At the same time, non-isothermal crystallization kinetic studies of neat sPB and 1/2.5 blends were carried out by DSC. The Avrami equations modified by Jeziorny and Privalko, were used to fit the primary stage of the non-isothermal crystallizations of neat sPB and the 1/2.5 blends. A larger Avrami exponent for neat sPB than for the blends was observed, and possible reasons are discussed. The activation energies (DeltaE) were determined to be -88 and -106 kJ mol(-1) by the isoconversional Friedman method for neat sPB and sPB in the blends, respectively. (C) 2004 Society of Chemical Industry.