Polypropylene/calcined shell composites: Processing and properties

Polypropylene (PP) composites are prepared using calcined shell waste (CS) at 8% by weight, with incorporation of Polyethylene grafted with maleic anhydride (PE-g-MA). For comparison purposes, the composites are mixed using either a single-screw extruder (SSE) or a twin-screw extruder (TSE), followed by injection molding. The composites (SSE) with the addition of 10 wt% PE-g-MA showed a reduction in fluidity of approximately 40.78 %, while those produced using TSE showed a 40% decrease. The impact strength of PPCSPE-g-MA10 (TSE) decreased by around 37.92%, while the composites with fine CS showed improved performance. The elongation at yield was reduced by 12.30% for SSE samples, while an increase of 21.26% was observed for composite with 2 wt% PE-g-MA processed by TSE. The yield stress and tensile strength were slightly reduced for TSE samples, while SSE composites showed a similar performance to pure PP. A slight increase in tensile modulus was observed in all composites. The flexural modulus of the composites with 2 wt% PE-g-MA showed better results, with an increase of 21.6% (TSE) and 18.4% (SSE). Flexural strength was higher in the SSE composites, attributed to better dispersion and adhesion of fine CS particles. The analysis of variance (ANOVA) revealed statistically significant differences in the mechanical properties of the composites. Both the Nicolais-Narkis and Pukanszky models demonstrated that the addition of compatibilizer positively influences interfacial adhesion. The initial thermal stability of the PPCSPE-g-MA composites decreased by no more than 13%. A promising solution for the industrial recycling of calcined residue is evaluated.