In this work, thermal expansion and morphological properties of recycled polypropylene wood flour composites were evaluated in order to verify the effect caused by the usage of a natural oil as coupling agent. The natural oil used as coupling agent was octanoic acid (C8), maleic anhydride grafted polypropylene (MAPP), widely used in industry but from non-renewable source, was also used for comparison. Composites were obtained by twin screw extrusion and injection molded. The results showed that the addition of octanoic acid and maleic anhydride grafted polypropylene reduced the coefficient of thermal expansion of the composites. The dependence of melt viscosity obeyed the Arrhenius-Eyring expression, and the activation energy values for composite viscous flow were higher than matrix. The composite morphology revels that octanoic acid promotes strong interfacial adhesion between filler and matrix, similar to that observed when maleic anhydride grafted polypropylene were used. Octanoic acid showed similar results when compared with maleic anhydride grafted polypropylene in all properties evaluated, indicating that can be used as an alternative instead of use coupling agent from non-renewable sources.