Preparation, analysis and applications of rubber seed oil and its derivatives in surface coatings

Rubber seed oil (RSO) and its derivatives, heated rubber seed oil (HRSO) and alkyd resins were evaluated as binders in air drying solvent and waterborne coatings. HRSO was obtained by heating RSO at 300±5 °C until the desired viscosity. Acid value of RSO (53) is somewhat high. The major saturated fatty acids are palmitic (10.2%) and stearic (8.7%) while the main unsaturated fatty acids are oleic (24.6%), linoleic (39.6%) and linolenic (16.3%). Naturally, RSO is semi-drying and heating enhances its drying ability. GPC analysis reveals that RSO consists of a rather high molecular weight fraction that is rarely found in commonly known vegetable oils. The average molecular weight of RSO is higher than that of HRSO with the latter narrower in molecular weight distribution. Low molecular weight species constitute greater proportion of the alkyds and their number average molecular weights range between 1379 and 3304 which are comparable to those of commercial alkyds. The narrower the size distribution the better the quality of these alkyds as binders. Physico-chemical properties of solvent-borne alkyds vary with oil length (OL) and they are optimum at 50% OL. Water-borne alkyds investigated show that the sample with lower oil content contains lower volatile organic content. All the alkyd samples and HRSO are fairly resistant to water and alkali while they are virtually unaffected by acid and salt solutions. However, samples IV and V (water-borne alkyds) are more resistant than their solvent-borne counterparts (samples I-III) but exhibited lower scratch/gouge pencil hardness.