Utilization of spent coffee grounds as fillers to prepare polypropylene composites for food packaging applications

Biomass-derived wastes as the additive of nondegradable plastics have been paid more attention due to the ever-growing environmental pollution and energy crisis. Herein, the spent coffee grounds (SCG) have been used as fillers in polypropylene (PP) after the heat treatment to realize its recycling utilization. The effect of the heat treatment atmosphere on the properties of the obtained SCG and SCG/PP composites has been investigated systematically. The results show that the residual coffee oil can be removed more thoroughly under an air atmosphere than under a nitrogen atmosphere at a relatively low cost and an eco-friendly process. The lower residual oil rate of SCG is beneficial to improve the comminution and further enhance the affinity with the PP matrix. The obtained SCG/PP composites hold lower water absorption, higher hydrophobicity, and better mechanical properties, implying their potential applications in the field of food packaging. RESEARCH HIGHLIGHTS: Spent coffee grounds have been used as fillers in PP after the heat treatment. The heat treatment in the air is more favorable for the removal of the coffer oil of SCG. The low residual oil rate in SCG can improve its comminution and affinity with PP. The SCG/PP composites hold excellent performances for food packaging applications.