Lightweight and strong fibrillary PTFE reinforced polypropylene composite foams fabricated by foam injection molding.

• Nano PTFE Fibrils well dispersed in PP matrix improved melt strength and crystallization behavior pronouncedly. • Nano PTFE fibrils decreased the cell size while increased the cell density effectively. • Injection molded PP/PTFE foams had an unprecedentedly increased impact strength up to 250.4% compared with PP foams. • This work made foam injection molding a promising future, to fabricate injection molded lightweight and strong polymer foams. Polypropylene (PP) shows wide applications in many industries, especially for automotive. To save resources and energy, lightweight is an essential pursuit for industrial products. Foam injection molding (FIM) is a cost-effective method to manufacture lightweight plastic products, but it is still challenging to fabricate high-performance PP microcellular products for structural applications. Herein, a facile way was reported to produce lightweight and strong foamed PP/polytetrafluoroethylene (PTFE) components. First, in-situ fibrillated PP/PTFE composites were prepared using a co-rotating twin-screw compounder. SEM analysis showed nanoscale reticular PTFE fibrils uniformly dispersed in PP matrix. DSC combined with online optical microscopy observation, and rheological analysis demonstrated PTFE fibrils pronouncedly improved crystallization and viscoelasticity, respectively. Thus, PP/PTFE foam showed obviously refined cell structure compared with PP foam. Thanks to the promoted crystallization and refined cellular morphology, PP/PTFE foam exhibited superior mechanical properties, particularly in Gardner impact strength. The higher the PTFE content, the higher the impact strength. With a PTFE content of 5 wt%, the impact strength was increased by more than 250%. Furthermore, PTFE fibrils also facilitated to improve PP foam's tensile strength and modulus. Therefore, lightweight and strong PP/PTFE foam, achieved by the flexible, efficient, and scale-up FIM technology, exhibits a promising prospect in applications. [ABSTRACT FROM AUTHOR]