Effect of silicon dioxide on crystallization and melting behavior of polypropylene

Abstract

Abstract The crystallization and melting behavior of isotactic polypropylene (iPP) and polypropylene copolymer ( co ‐PP) containing silicon dioxide (SiO 2 ) were investigated by differential scanning calorimeter (DSC). SiO 2 had a heterogenous nucleating effect on iPP, leading to a moderate increase in the crystallization temperature and a decrease in the half crystallization time. However, SiO 2 decreased the crystallization temperature and prolonged the half crystallization time of co ‐PP. A modified Avrami theory was successfully used to well describe the early stages of nonisothermal crystallization of iPP, co ‐PP, and their composites. SiO 2 exhibited high nucleation activity for iPP, but showed little nucleation activity for co ‐PP and even restrained nucleation. The iPP/SiO 2 composite had higher activation energy of crystal growth than iPP, indicating the difficulty of crystal growth of the composite. The co ‐PP/SiO 2 composite had lower activation energy than co ‐PP, indicating the ease of crystal growth of the composite. Crystallization rates of iPP, co ‐PP, and their composites depended on the nucleation. Because of its high rate of nucleation, the iPP/SiO 2 composite had higher crystallization rate than iPP. Because of its low rate of nucleation, the co ‐PP/SiO 2 composite had lower crystallization rate than co ‐PP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1889–1898, 2006