Syndiotactic polypropylene-based elastomer as promising toughening agent for waste appliances-derived polypropylene

The rapid replacement of household appliances has generated a significant amount of waste appliances-derived polypropylene (WAPP), presenting a valuable resource for recycling. However, the long-term use and subsequent thermal processing of WAPP lead to its degradation, significantly impairing its toughness. Herein, syndiotactic polypropylene (sPP) as a novel toughening agent was investigated to achieve the efficient toughing of WAPP. The incorporation of 15 wt% of the sPP-based elastomer increased the impact strength of WAPP to 29.2 kJ/m2 (25 °C), which was 5.7 times that of the unmodified one and 1.9 times that modified with polyolefin elastomers (POE). This inspiring effect originates from the structural similarity between isotactic and syndiotactic polypropylene, which not only achieves a more uniform dispersion of the rubbery phase, but also creates micro voids between the phases due to the incompatibility of sPP and iPP, making it easier for shear bands to form. Further, the contradiction between rigidity and toughness is reconciled by introduction of talcum powder. This comprehensive investigation into the effects of the sPP-based toughening agent on the composite material's properties expands the potential applications of sPP and enhances our understanding of its toughening mechanisms.