Olive stones flour as reinforcement in polypropylene composites: A step forward in the valorization of the solid waste from the olive oil industry

Abstract

The usefulness of olive stone flour (OSF) from the solid residue of the olive oil extraction as a reinforcement for the preparation of a cost-effective polypropylene-based composite was investigated. The lignocellulosic filler consisted of acicular particles with a broad size distribution ranging from about 50 to 400μm, and is composed of lignin, hemicelluloses, and cellulose. Composites with filler loading up to 70wt% were prepared using a melt processing and injection molding. The evolution of the mechanical performance, impact properties, and water absorbance of the composites as a function of the filler content were investigated. The addition of a maleated polypropylene (MAPP) coupling agent at a level of 5%, with respect to the filler, was shown to be essential in bringing about a reinforcing effect. A steady increase in the modulus along with a preservation in the tensile strength was observed up to a content of 60% OSF. The obtained results have confirmed the viability of OSF as cheap reinforcing filler for the PP matrix; thus, opening new perspectives for the use of this agricultural by-product.