Synthesis and Characterisation of Cardanol Acetate and Cardanol Ether as Reactive Diluents for Alkyd Coatings

Abstract

Alkyd resins are viscous, tacky materials that are difficult to handle. Most often, these handling problems are overcome by dissolving the resins in organic solvents, which evaporate into the atmosphere as volatile organic compound (VOC), giving rise to regulations. A reactive diluent is a compound that acts as a solvent in the liquid paint, lowering the viscosity, and chemically reacts into the final film during the curing process to give a more environmentally friendly coating and the amount of traditional solvent can be decreased. Cashew nut shell liquid (CNSL) is not currently utilized in Kenya and the objective of this work was to develop reactive diluents from chemically modified CNSL products and evaluate their compatibility with alkyd coatings. A standard reactive diluent should have low viscosity, increase drying time of less than 50 %, and be nontoxic. Cardanol was isolated using methanol and ammonia solution as the solvents in a ratio of 8:5 respectively. The percentage yield of cardanol obtained was 63.94 %. The yield of cardanol acetate obtained was 58.94 %. The cardanol acetate was also characterized by FT-IR and it showed the presence of the C=O stretch functional group characteristic of the ester and the absence of the OH group that was present in cardanol. The cardanol acetate synthesised showed a low viscosity (45 Cps) and a reduced drying time of about 25–35% compared to conventionally prepared formulations.

Keywords: Cashew nut shell liquid, Cardanol, Reactive diluent, Cardanol acetate.