Understanding the physicochemical properties of olive kernel to be used as a potential tool in the development of phenol-formaldehyde wood adhesive

During olive oil production process, a great number of by-products are generated, including olive kernel. These by-products can be used for the development of new products for use in many different industrial applications. The evaluation of the physicochemical properties of these by-products constitutes a key factor in evaluating the potential reutilization of olive oil by-products. In the present study, the physicochemical properties of olive kernel were analyzed. Fourier transform infrared spectroscopy (FT-IR), cross-polarization magic angle spinning 13C nuclear magnetic resonance (CP/MAS 13C NMR), Brunauer, Emmett and Teller (BET), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) techniques were used. FT-IR and CP/MAS 13C NMR analysis showed that olive kernel contained typical functions of cellulose, hemicelluloses and lignin. Morphological studies revealed different sizes and arrangements of cells, showing that olive kernel had an irregular structure. TGA showed that thermal stability was observed up to approximately 180 °C. In the present work it was found that olive kernel has the potential to act as a replacement material for up to 15% of base resin in a PF-based adhesive, whilst exhibiting similar or better adhesive properties than a commercial PF resin.