Cardanol-based Resol Phenolics – a Comparative Study

Cardanol, a renewable agro-byproduct, can be substituted for phenol in phenol–formaldehyde resin (PF). However, resins made solely from cardanol have inferior mechanical properties. In this study, we synthesised a number of phenol–cardanol–formaldehyde (PCF), phenol–formaldehyde (PF) and cardanol–formaldehyde (CF) resins. In all these cases, the molar ratio of total phenol to formaldehyde (P:F) was maintained at 1:1.75. Subsequently, PF and CF resins were mechanically mixed in such a way as to produce phenol– formaldehyde–cardanol formaldehyde blends (PFCF) with the same total phenol to cardanol ratios as in the case of PCF resin. The mechanical, abrasive and thermal properties of the PCF and PFCF resins were studied to optimise the phenol to cardanol ratio and also for comparison of the properties of these two resins. The tensile and flexural strength decreased with incorporation of more cardanol units into the phenolic resin. However, an increase in impact strength is observed for both PCF and PFCF resins with up to 4–6 mol.% cardanol. The thermal properties of phenolic resin are negatively influenced by cardanol content. Between PCF and PFCF resin, PFCF shows better thermal stability.