Phthalic acid and isophthalic acid are isomers with each other. The unsaturated polyester molecular chains synthesized by them are o-benzene type and m-benzene type, although their molecular chains are similar in chemical structure, but m-benzene type unsaturated Compared with o-phthalic unsaturated polyester, polyester has the following characteristics:
① Isophthalic dicarboxylic acid can be used to prepare higher molecular weight isophthalic acid unsaturated speech ester, so that the cured products have better mechanical properties, toughness, heat resistance and corrosion resistance;
② The purity of isophthalic polyester, and no impurities of isophthalic acid and low molecular weight isophthalate remain in the resin;
③ The ester bond on the isophthalic polyester molecular chain is protected by the steric hindrance effect of isophthalic acid. The ester bond on the phthalic polyester polyester molecular chain is more susceptible to attack by water and other corrosive media. The glass fiber reinforced plastics made of isophthalic polyester resin still have quite high performance after soaking in 71℃ saturated sodium chloride solution for one year.