Non-isothermal crystallization kinetics of polypropylene homopolymer/impact copolymer composites

Crystallization kinetics of an isotactic homopolymer polypropylene (HPP), an impact copolymer polypropylene (ICPP), and their composites were studied in this work. The Avrami–Jeziorny and Mo models successfully described the crystallization process. When the ICPP content increased, the crystallization rate first increased and then decreased with the highest crystallization rate at the ICPP content of 60 mass%. The nucleation activity kept increasing with the rise of the ICPP content, demonstrating that the rubber phase in the ICPP acted as a nucleating agent and prompted the nucleation process. The decrease in crystallization rate when the ICPP content was higher than 60 mass% might be caused by the decrease in chain mobility and the increase in crystal–crystal interactions. When the ICPP content exceeded 60 mass%, the crystallization activation energy increased evidently, indicating lower polymer chain mobility. Meanwhile, the Avrami exponent, n, decreased, suggesting limited crystal growth space and higher crystal–crystal interactions. The nucleation activity showed high correlations to the mechanical and thermal properties of the materials. The Avrami exponent also had relatively high correlations to these properties. The results improved the understanding of the crystallization behaviors of the HPP–ICPP composites and helped predict their potential mechanical behavior changes.