Polyvinyl Chloride Composites Filled with Olive Stone Flour: Mechanical, Thermal, and Water Absorption Properties Ilhem Naghmouchi, 1 Pere Mutj  e, 2 Sami Boufi 1 1 Faculty of Science, University of Sfax, LMSE-3000 Sfax, Tunisia 2 Department of Chemical Engineering, Group LEPAMAP, University of Girona, Girona 17071, Spain Correspondence to: S. Boufi (E - mail: Sami.Boufi@fss.rnu.tn) ABSTRACT: The production of olive oil leads to considerable amounts of solid waste mainly composed of hard woody endocarp called olive stones. The aim of this work is to explore the possible use of ground olive stones as fillers for polyvinyl chloride (PVC), to elab- orate a cost-effective composite material with a solid loading of up to 50 wt %. After grinding, the ensuing olive stone flour (OSF) was incorporated into a PVC matrix via melt compounding and injection molding to elaborate PVC-OSF-based composites with a fil- ler content up to 50 wt %. The evolution of the mechanical performance, the impact property, the water absorbance, and wear resist- ance behavior, according to the OSF content, were investigated. The addition of OSF was shown to enhance the stiffness of the matrix, but at the expense of its mechanical strength. However, the strength of the composite did not fall as low as 30 MPa, and therefore, meets the requirements for many applications in plastic-based materials. The thermal properties of the ensuing composites were also studied by thermogravimetric analysis. The results show that the addition of OSF may be effective in increasing the stiffness of the PVC-based composite and in reducing the solid residue in the olive oil industry production. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41083. KEYWORDS: agricultural by product; composites; mechanical properties; olive Received 16 March 2014; accepted 30 May 2014 DOI: 10.1002/app.41083 INTRODUCTION Spain, Greece, Italy, Tunisia, and Turkey are the most important olive oil producers in the Mediterranean basin representing about 95% of the world production. 1 Tunisia is a leading olive oil producer, with over 65 million olive trees grown on 1.7 mil- lion hectares and an average annual production amounting to 200 3 10 3 T. The undeniable nutritional merits of olive oil are well-known; thus, the increasingly demand for it. However, the extraction process generates an “aqueous sludge” and a solid residue called “olive cake,” which is obtained after extracting the oil from the fruit. Currently, from 100 kg of olives, about 20% of oil is recovered, and 30% of olive cake and about 50% of aqueous liquor generated. Due to their high phenolic con- tent, the latter two fractions are not easily degradable by natural processes, and their disposal creates a major environmental issue in the main olive-producing countries. Accordingly, research into finding new possible uses for olive industry by-products, particularly the solid ones, is of a great relevance not only to the economy but also to the environment in these countries. Different strategies have been reported in the literature to valor- ize the solid by-products generated by the olive oil extraction, to reduce the negative environmental impact. The solid waste can be burned to produce electric energy or heat, 2 or turned into activated carbon 3 after a thermal treatment for the removal of poisonous metals from water. 4 The possible use of the solid by-products as a source of compost material has also been approached. 5–11 The conversion of olive stone flour (OSF) into viscous polyols, likely to be used in polyurethane foams, was successfully accomplished by total and partial oxypropylation. 12 The use of the ground solid waste as a sustainable filler in polymer-based composite also constitutes an interesting poten- tial application within the field of materials technology. In fact, given the high hardness of the olive stones, an enhancement in the stiffness of the polymer when the ground olive stone residue is incorporated within thermoplastic polymer matrix, might be expected. Although wood flour remains the main lignocellulosic filler 13,14 among the natural reinforcements, the use of agricul- tural by-products as a source of renewable filler or reinforce- ment in the production of plastic composites alleviates the shortage of wood resources, thus constituting an interesting alternative for making a bio-based composite. Despite the con- siderable amount of solid waste generated by olive oil extrac- tion, to the best of our knowledge, only a few research works V C 2014 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2014, DOI: 10.1002/APP.41083 41083 (1 of 10)