Phenolic molding compounds are the oldest synthetic plastic produced and used by mankind. Despite their old age, they are still in use today. Due to their excellent thermal and electrical properties, and fair price, they find use in various applications. However, one major drawback of phenolics is their lack of recycling option, landfilling being the main route of disposal. An alternative recycling method is proposed in this work. It relies on the use of comminuted phenolic compounds as a filler in a thermoplastic matrix. When this phenolic filler is incorporated without modification in a non-polar or polar polymer, poor adhesion is observed between the two phases as well as a decrease of the mechanical properties of the composite. In order to obtain a reactive organic filler by improvement of interfacial functional group reactions, different types of surface modification of the filler were performed. They depend on chemical reaction of two potentially reactive sites of the phenolic compound surface. On one hand, attempts were made to graft organosilane on phenolic hydroxyls. Two types of silane were used: an aminosilane and a vinylsilane. On the other hands, reaction of unsubstituted ortho and para carbon position of aromatic ring were attempted to graft β-amino-carbonyl molecules onto phenolic molding compound (Mannich reaction). Formaldehyde and various diamine were used. All reactions were carried out in a three necked round flask with a stirrer under reflux. The efficiency of the grafting reactions was evaluated with different techniques. Fourier transform infrared spectroscopy was used to assess the formation of the expected chemical bonds, as well as 13C NMR. In the case of silane treatment, the amount of grafted silicium was evaluated with EDX and 29Si RMN. The surface energy of the modified fillers was also measured. Finally, the modified fillers were incorporated in a polymer matrix and the mechanical properties of the composites were measured.