Polyester resins based on soybean oil: synthesis and characterization

Discovering renewable energy resources is receiving increased attention both in industrial and academic research. Vegetable oils are a promising route to renewable chemicals and polymers due to their ready availability, inherent biodegradability, and low toxicity. Also, bio-renewable fuels have been prepared from vegetable oils. Here, the soy oil monoglyceride has been obtained from the soybean oil by alcoholysis, and its structure was confirmed by the spectral analyses. To increase the yield of the monoglyceride formation and to prevent the ester interchange reversible reaction, we found that rapid cooling of the mixture with high-speed stirring allowed the best yield of soy oil monoglyceride. Then, three new polyester resins have been synthesized by the reaction of the monoglyceride with phthalic and/or maleic anhydrides with different ratios. The synthesized resins have been characterized by spectral analyses, and their morphological and physico-chemical properties such as acid value, iodine value, volatile matter content, and viscosity have been studied. The three polyester resins were soluble in common organic solvents. The effect of phthalic and maleic anhydrides ratio on the physical and chemical properties of the resin was also studied. The incorporation of maleic anhydride decreases the iodine value of the resins compared to phthalic anhydride-based resin.