Common Structures of Polyester Resins

The main raw materials for synthesizing saturated polyester resin are binary alcohols, binary acids, and ternary alcohols, with some also having monohydric alcohols or monohydric acids. The most commonly used alcohol is neopentyl glycol, whose ester has significantly better water resistance than ethylene glycol and propylene glycol. Ternary alcohols are mainly trimethylolpropane and trihydroxyethyl ethane. The most commonly used aromatic dicarboxylic acid is isophthalic acid. Due to its superior salt spray resistance, chemical resistance, and water resistance compared to phthalic acid, isophthalic acid is more commonly used in polyester resins. Aliphatic dicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid are also used in the synthesis of polyester resins, with adipic acid being more commonly used. Most resins contain aromatic and aliphatic dicarboxylic acids, and the molar ratio of aromatic to aliphatic dicarboxylic acids is the main factor controlling resin Tg.