Effect of alkaline-treated spent coffee grounds and compatibilizer on the mechanical properties of bio-composite based on polypropylene matrix

Abstract

In this study, the effect of alkaline-treated spent coffee grounds and compatibilizer on the mechanical properties of bio-composite based on polypropylene (PP) matrix was investigated. After alkaline treatment, the surface of spent coffee grounds became rougher; hence the PP matrix could better adsorb and encapsulate the treated coffee grounds compared with that of untreated ones. The TGA analysis shows that the alkaline treated spent coffee grounds had better thermal properties than the untreated ones. When increasing the weight percentage of spent coffee grounds from 10 to 20, the tensile strength and flexural strength of PP-based composite decreased. These mechanical properties of PP-based composite containing treated coffee grounds were enhanced compared with that containing untreated coffee grounds due to the better dispersion of treated coffee grounds into the PP matrix. The presence of polypropylene-graft-maleic anhydride (PP-g-MA) compatibilizer at the content of 1, 3, and 5 wt% led to a significant increase the mechanical properties of PP-based bio-composites, reaching the highest tensile strength of 22.7 MPa and flexural strength of 17.3 MPa. Therefore, the alkaline-treated spent coffee ground is a potential additive for producing bio-composite with the advantages of being light and easy to naturally decompose.