Lightweight and strong polypropylene/talc/polytetrafluoroethylene foams with enhanced flame-retardant performance fabricated by microcellular foam injection foaming

Abstract

With the ever-increasing demand for plastic structural components, the development of lightweight plastics is critical for environmental protection and reduced material consumption. Foam injection molding exhibits promise for manufacturing lightweight products, and hence, could be explored for the fabrication of foamed polypropylene (PP) parts. However, it is challenging to fabricate high-performance foam-injection-molded polypropylene (FIM-PP) foams due to the low melt strength of PP. Herein, we have proposed a novel method to prepare lightweight and strong ternary-blended PP foams with enhanced flame retardancy by incorporating in situ-fibrillated polytetrafluoroethylene (PTFE) and talc. The PTFE nanofibrils and talc effectively improved the melt viscoelasticity and crystallization of PP; hence, both, regular and mold-opening foam-injection-molded (MOFIM) ternary-blended PP foams, exhibited refined cellular structures. Furthermore, the MOFIM-PP/Talc/PTFE foam exhibited remarkable mechanical performance, including a 341% increase in the tensile toughness, 408% increase in the notched impact strength, and 121% increase in the flexural strength, which were attributed to the enhanced brittle-to-plastic transition by PTFE nanofibrils and the refined cellular structure. These advantages, combined with the enhanced flame retardancy of the MOFIM-PP/Talc/PTFE foam, make this method cost-efficient, scalable, and green to manufacture lightweight and strong PP foams, thereby broadening the application scope of PP in structural components.