| Abstract: | Abstract Nonisothermal crystallization of the neat isotactic polypropylene homopolymer (PP‐0) and of the nanocomposite containing 4.68 wt.% of organosilica (PP‐4.68) was studied in the standard differential scanning calorimetry (DSC) mode during constant‐rate cooling from the melt state. Analysis of the nucleation parameters derived from cooling rate dependencies of the temperatures for the onset of crystallization exotherms suggested a slight increase of the nucleation barrier for lamellar crystallization of PP within a confined space between neighboring nanoparticles of an infinite cluster of the nanocomposite, concomitant to stronger restrictions to transport of PP segments across the melt/lamellar crystal interface. The overall crystallization rate data for PP‐4.68 were consistent with the assumption of two separate contributions from the initial (unconstrained) and the subsequent (constrained) nucleation mechanisms, respectively. The obtained results were considered as evidence for a coexistence in an undercooled PP melt of the nanocomposite of initial nucleation sites characteristic for the neat PP‐0, and the basically different nucleation sites (presumably, PP chains anchored by both ends to the surfaces of two adjacent nanoparticles). |
