Enhancing Crystallization and Toughness of Wood Flour/Polypropylene Composites via Matrix Crystalline Modification: A Comparative Study of Two β-Nucleating Agents

• Published in: Polymers Vol. 14; no. 17; p. 3561
• Main Authors: Luo, Shupin, Lv, Chao, Chang, Liang, Guo, Wenjing
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 29.08.2022; MDPI
• Subjects: Calcium carbonate; Comparative studies; composite; Composite materials; Crystal structure; Crystallinity; Crystallization; crystallization behavior; Fillers; Flour; Impact strength; Mechanical properties; Morphology; nucleating agent; Polymer matrix composites; Polymer melts; Polyolefins; Polypropylene; Self-assembly; Spherulites; Tensile strength; Thermoplastics; Toughness; wood filler; β-nucleation; China
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym14173561

Incorporation of short wood fillers such as wood flour (WF) into polypropylene (PP) often results in a marked reduction of toughness, which is one of the main shortcomings for WF/PP composites. This research reports a facile approach to achieve toughening of WF/PP composites via introducing self-assembling β-nucleating agents into PP matrix. The effect of two kinds of nucleating agents, an aryl amide derivative (TMB5) and a rare earth complex (WBG II), at varying concentrations on the crystallization and mechanical properties of WF/PP composites was comparatively investigated. The results showed that both nucleating agents were highly effective in inducing β-crystal for WF/PP, with β-crystal content (kβ) value reaching 0.8 at 0.05 wt% nucleating agent concentration. The incorporation of TMB or WBG significantly decreased the spherulite size, increased the crystallization temperature and accelerated the crystallization process of WF/PP. As a result of PP crystalline modification, the toughness of composites was significantly improved. Through introducing 0.3 wt% TMB or WBG, the notched impact strength and strain at break of WF/PP increased by approximately 28% and 40%, respectively. Comparatively, although WF/PP-WBG had slightly higher Kβ value than WF/PP-TMB at the same concentration, WF/PP/TMB exhibited more uniform crystalline morphology with smaller spherulites. Furthermore, the tensile strength and modulus of WF/PP-TMB were higher than WF/PP-WBG. This matrix crystalline modification strategy provides a promising route to prepare wood filler/thermoplastic composites with improved toughness and accelerated crystallization.