Correlative studies on the properties of rubber seed and soybean oil-based alkyd resins and their blends

Abstract

This study aims at synthesizing alkyd resins from rubber seed oil (RSO), soybean oil (SBO), and their blends via the monoglyceride route. Oil extracted from rubber seeds was blended with soybean oil at various blending ratios (80:20, 70:30, 50:50, 30:70, and 10:90). Thereafter, the blends were employed in the synthesis of polyesters (alkyd resins) via alcoholysis technique. The alkyd samples synthesized from the RSO, SBO, and their respective blends were characterized for comparative purpose. The RSO-/SBO-based alkyds and aforementioned blends have iodine values of 157.90/142.00, 152.44, 149.90, 143.16, 142.26, and 142.41 gI2/100 g and saponification values of 216.21/228.61, 203.67, 171.04, 161.97, 142.89, and 135.62 mgKOH/g, respectively. The drying property (set-to-touch time and the tack free) of the 100% RSO-based alkyd resin did not experience any significant improvement as the blending proportion of SBO in RSO increases. The tack-free and dry-through times for the blends were estimated to be around 129–133 and 236–243 min, respectively. Huggins and Kraemer viscosity relationship was used to extrapolate the intrinsic viscosities of the RSO- and SBO-based alkyds and their corresponding blends. The blends showed resistance to brine, water, and acid. However, only some exhibited fair resistance to alkali. The results from the investigation revealed that the alkyds prepared using a blend of RSO/SBO oil possess coating properties whose values are comparable to those of commercial polyesters. However, the studied SBO cannot be considered as good blending oil with RSO for the preparation of alkyd for the improvement of drying properties.