Study On Preparation And Properties Of Unsaturated Polyester Resin With Low Phenyl Content

The weatherability of the unsaturated polyester (UP) resins is advanced by two ways—new structure units brought into molecule chains and crosslinking agent improved. QUV exposure experiments and EIS tests are made to evaluate the weatherability of the resin synthesized. To satisfy the requirements as gel coat ,the way to forecast the viscosity of UPR and the thixotropy of gel coat are also discussed. The results indicate as follows:A new kind of unsaturated polyester resins(UPR) with excellent weatherability and perfect mechanical properties has been synthesized by molecule structure design to bring in a new structure-unit 1,4-cyclohexanedicarboxylic acid (CHDA) . The reaction time of the UPR is shortened. Phenyl ring group is replaced by naphthenic ring group in the UP and the molecule percent of phenyl ring groups has reduced by 25% to improve the weatherability greatly. The CHDA-UPR is compared with isophthalic acid UPR in mechanical properties.The result indicates CS containing naphthenic ring group compared with PTAS containing phenyl ring group ,the tensile strength is stronger than the latter, impact strength is almost equal to the latter, hardness decreases a little.The substance mentioned are also analysed by FTIR.Crosslinking agent methylmethacrylate(MMA) is selected through comparing mechanic properties, replacing styrene partly to enhance weatherability. By FTIR, optics microscope, mechanical properties retention etc. . Weatherability of PTAS, CS, CMS is tested and the sequence is CMS>CS>PTAS before and after QUV exposure.The weatherability of different UP resins are evaluated by EIS and mechanisms are discussed primarily. EIS plots and change trends of fitted parameters of equivalent circuit model indicate CS and CMS with naphthenic ring group excel PTAS with phenyl ring group . At the same time it is proved that EIS is a good means to detect the UPR weatherability.