Evaluation of Cashew Nut Shell Liquid Based Products as Reactive Diluents for Alkyd Coatings

Abstract

Volatile Organic Compounds (VOCs’) have aroused concern in many parts of the world especially in large cities due to their negative impacts to the environment. In the presence of sunlight, VOCs’ react with NO gases to produce tropospheric ozone, a powerful oxidant and pollutant to the atmosphere. Although most of the VOCs’ originate from petroleum products and internal combustion engine exhausts and plants, a significant amount is derived from solvent based coatings. This study reports the findings of environmentally friendly and less toxic reactive diluents synthesized from Cashew Nut Shell Liquid (CNSL) based products. CNSL is a by-product from cashew nut processing and contains anarcardic acid, cardol, 2-methyl-cardol and cardanol, decarboxylated anarcardic acid. CNSL is not currently utilized in Kenya. It was extracted from cashew nut shells by cold solvent extraction process using nhexane

solvent. The percentage yield of CNSL obtained was found to be 30.9 ± 0.2. 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 63.93 ± 0.2%. Cardanol was modified via transesterification and methylation with acetic anhydride and methyl iodide, respectively. The percentage yield of cardanyl acetate obtained was 58.94 ± 0.01% and that of cardanyl methyl ether was found to be 52.39 ± 0.01%. Cardanol, cardanyl methyl ether and cardanyl acetate were also characterized using Finnigan Gas Chromatography Mass Selective Detector 8000 and a parent peak of m/z = 108 observed for all the three products. The effects of cardanyl methyl ether, cardanyl acetate and neat cardanol on the properties of alkyd-based coatings film were x investigated including pencil hardness which was found to be 4H for all the formulations compared to 5H for the control. Coatings formed had good adhesion, good drying time and pencil hardness and would be expected to be cheaper since Cashew Nut Shell Liquid is a renewable raw material from waste. VOCs’ reduction was achieved to the extent of 39% compared to conventional commercial products. Drying time study showed that drying time can be altered variously by types and level of diluent added.