Thermal analysis and successive self-nucleation and annealing (SSA) treatment of synthesized bimodal polypropylene (BPP) reactor blends using homogeneous binary metallocene catalyst

Abstract

Several polypropylene (PP) reactor blends were synthesized using homogenous binary metallocene catalytic systems composed of isospecific (I): rac-Me2Si(2-Me-4-Ph In)2ZrCl2 and oscillating (II): (2-Ph In)2ZrCl2 catalysts. The reactor blends were analyzed using gel permeation chromatography and differential scanning calorimetry. All the blends showed bimodal molecular weight distribution, and the MWs were shifted toward higher values compared with PPs synthesized with each of individual catalysts showing some probable interactions between the two active sites. Self-nucleation and annealing treatment on hexane-insoluble–heptane-soluble parts of the PP reactor blends showed that as the II/I molar ratio increases from 0 to 40 in the binary system, multiplicity of the endotherm peaks increases from 1 to 7, which is indicative of the presence of various lamellar thicknesses in the samples. Wide-angle X-ray scattering studies on the PP reactor blends confirmed that the blends have isotacticities and crystallinities between those of polymers obtained by the individual catalysts.