Composite materials from unsaturated polyester resin and olive nuts residue: The effect of silane treatment

Olive nuts flour (ONF) from the solid waste of the olive oil extraction was used as a cost-effective filler to reinforce unsaturated polyester resin matrix composites. Composites with filler loading from 10 to 60 wt% were prepared by compression molding using untreated and γ-mercaptopropyltrimethoxysilane (MRPS)-modified ONF. The evolution of mechanical performance, dynamic mechanical properties, impact properties and water absorbance, were investigated as a function of the filler content. The changes in the mechanical properties as well as the water absorption behavior were shown to be greatly affected by the silane treatment of the filler. A better enhancement in the stiffening effect and a reduction in water absorption were noted when silane treated ONF was used. Evidence of the improvement of the interfacial adhesion following the silane modification was supported by dynamic mechanical analysis (DMA) and SEM observation. These results were explained in terms of the improvement in the interfacial adhesion between the filler and the matrix through the aptitude of the MRPS to provide a chemical connectivity between the two phases.