Evaluation studies on the Application of vernonia and other epoxidized Vegetable oils in alkyd and epoxy coatings.

Abstract

Vernonia oil and other epoxidized vegetable oils were studied for their characteristics and evaluated for their applications as reactive diluents in alkyd coatings and in elastomers for toughening epoxy coatings. These oils are compatible with short oil, medium oil and long oil alkyds. Their degree of epoxidation was found to be related to their densities, viscosities unsaturation and rate of cure of alkyd coatings (with the oils as reactive diluents). The oils helped to lower volatile organic compounds (VOC), drying time and application viscosity of alkyd based paints. The paints maintained package (can) stability very well. Coatings formed had excellent adhesion, flexibility, impact resistance and had good specular gloss. The oils did not enhance degradation of the coatings by UV. Compared with synthetic reactive diluents, introduction of these oils into alkyd coatings would be simpler and possibly involve less capital investment. They are cheaper with little or no toxicity. Th ir use would reduce pollution to the atmosphere and save on expensive solvents and energy. Two phase epoxy coatings were made from DGEBA epoxy resin (EPON 828), commercial 4,4'-diaminodiphenylmethane (DDM) and epoxidized vegetable oil liquid rubber. Below 20% rubber content, discrete rubbery particles of the order of 0.2-5 microns were formed in the epoxy matrix. In this region, microcavitation and shear band formation were the major toughening mechanisms of the coatings. Beyond 20% rubber content, phase inversion started in the xvii coatings and was complete by 50%. In this region, epoxy coatings were enhanced by rubber through its flexibilizing and plasticizing effects. Incorporation of the liquid rubber in the epoxy coatings helped to improve on impact resistance and flexibility. Adhesion showed no significant change but remained high throughout. There was a gradual decrease in hardness as rubber content was increased. Epoxidized vegetable oils have great potential in alkyd coatings and elastomers for toughening epoxy coatings.