Study of the Physico-Chemical Properties of Injection-Molded Polypropylene Reinforced with Spent Coffee Grounds

This study investigates the use of spent coffee grounds (SCGs) as a biofiller in polypropylene (PP) composites, produced via injection molding, as a sustainable alternative to conventional materials. The effects of varying SCG content (1%, 5%, 7%, and 10% w/w) on the flow behavior, thermal stability, mechanical properties, structural integrity, and morphology of the composites were systematically evaluated. Analyses using optical microscopy (OM) and Fourier-transform infrared spectroscopy (FT-IR) revealed significant changes in morphology and structure with SCG addition. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed improved thermal stability with increasing SCG content. Mechanical characterization indicated an enhanced hardness and tensile modulus, a near-constant tensile strength, and a decreased toughness and elongation at break with increasing SCG content. Melt flow index (MFI) measurements confirmed suitable processing characteristics. Overall, the PP/SCG composites demonstrate promising performance regarding sustainability and mechanical properties, suggesting their viability as an alternative to traditional materials.