Investigating the optimum unsaturated fatty acid content and oil length for auto-oxidative drying of palm-stearin-based alkyd resin

Abstract

Abstract The pendant chain of the Palm Kernel Stearin (PKS) was modified by blending it with measured ratio of rubber seed oil (RSO), followed by dehydration of the oil blend with the aim of increasing the degree of unsaturation in the oil chain. The modified dehydrated palm kernel stearin oil blend with ratio of 80:20, 75:25,70:30 and 65:35 by wt/wt% of PKS to RSO, respectively, were used to synthesized four different medium oil length alkyds, labelled as Alkyd A, Alkyd B, Alkyd C and Alkyd D, respectively, using a two stage alcoholysis-polyesterification method. The film properties of the synthesized alkyds were determined by carrying out the physico-chemico-mechanical properties and drying test of the Alky A to Alkyd D. The aim was to get the optimum ratio of PKS to RSO which will give the best and suitable result as regards to the total PKS content of the oil blend. The alkyd resin synthesized with 70:30 (by wt/wt%) of PKS to RSO (alkyd C) yields the best result with respect to the three other oil blend series. Also, the effect of oil length variation were investigated, which leads to the production of two additional alkyd resin labelled as Alkyd C S and Alkyd C L with the same oil blend ratio with respect to alkyd C but with short and long oil length respectively as regards to the fatty acid composition of the resin. From the results obtained, the film of Alkyd C S gave the best mechanical properties whereas the film of Alkyd C L has a good chemical resistance and drying properties as compared to Alkyd C and Alkyd C S , respectively. Overall, it can be concluded that for palm kernel stearin which is a saturated fatty acid to be utilized in the synthesis of a molecule of an auto-oxidative drying alkyd, approximately two − third of the total oil content must be blended with an unsaturated fatty acid (one unsaturation per molecule).