Phthalic acid and isophthalic acid are isomers of each other. The molecular chains of unsaturated polyester synthesized from them are o-phthalic and isophthalic, respectively. Although their molecular chains are similar in chemical structure, the isophthalic is unsaturated Compared with ortho-phthalic unsaturated polyester, polyester has the following characteristics:
①Isophthalic acid unsaturated polyester resin with higher molecular weight can be prepared with isophthalic acid, so that the cured product has better mechanical properties, toughness, heat resistance and corrosion resistance;
②The purity of isophthalic acid polyester is high, and there is no residual isophthalic acid and low molecular weight isophthalate impurities in the resin;
③The ester bond on the molecular chain of isophthalic acid polyester is protected by the steric hindrance effect of isophthalic acid. The ester bond on the molecular chain of phthalic acid polyester is more susceptible to attack by water and other corrosive media. The glass fiber reinforced plastic made of isophthalic acid polyester resin still has quite high performance after soaking in saturated sodium chloride solution at 71°C for one year.