Preparation and comparative analysis of neem and dehydrated castor seed oil alkyd resin paint coatings

Abstract

Coatings such as paint are made up of four important components; pigments, binders, solvent and additives. Gloss paint also known as oil paint used majorly alkyd resin as its binder. In this study, medium oil length alkyd resins were synthesized from Neem (Azadirachta indica) and dehydrated Castor (Ricinus communis) seed oils by alcoholysis. The alkyd resins were used to prepare gloss paints and their final properties were compared. The two seed oils were extracted with n-hexane in a soxhlet apparatus and their physico-chemical properties were determined. The acid values were 12.69 mgKOH/g and 12.64 mgKOH/g for castor and neem seed oil, respectively. The saponification and iodine values were 184.30 mgKOH/g and 97.61 gI2/100g, respectively for the castor seed oil, while the neem seed oil has saponification and iodine values of 192.35 mgKOH/g and 84.20gI2/100g, respectively. After dehydration, castor oil has iodine value of 131.00 gI2/100g which made it a drying oil. The Fourier Transform Infra-Red (FTIR) spectroscopic analysis of the medium oil length alkyd resins from dehydrated castor and neem seed oils revealed the same ester functional group at 1722.00 cm-1. The absorption at 2926.00 cm-1and 2922.20 cm-1 for dehydrated castor and neem seed alkyd resin, respectively showed aliphatic chain of their polyesters. The dehydrated castor alkyd paint has drying-through time of about 24 hours while the neem seed oil alkyd paint has drying-through time greater than 48 hours. It was discovered that the dehydrated castor seed alkyd resin paint showed better properties than neem seed oil alkyd resin paint.