Preparation, Characterization And Performance Study Of High Performance Polyester Containing Imide Structure

The polyethylene terephthalate?PET?is a kind of polymer which has the characteristics of low friction resistance,low hygroscopicity,good dimensional stability,excellent insulation performance,wide temperature range and good solvent stability.The PET has rapidly developed and become the synthetic fibers which possess the largest production at present.However,the low glass transition temperature limits its application in the high temperature field,so it is used to improve its heat resistance,and extend its application field,an imide monomer is added to perform the polycondensation modification.The polyimide?PI?is a kind of polymer with excellent thermal properties,chemical resistance,mechanical properties and electrical properties,etc.,and it is widely used in high-tech fields such as aerospace and microelectronics.The polyester is modified by introducing imide structure.Firstly,the monomer of imide structure is prepared,and the purity is characterized.Then the conditions for polycondensation reaction are explored to synthesize modified polyester with better performance.In order to explore the polymerization conditions of imide monomers synthesized by the reaction of pyromellitic dianhydride?PMDA?with ethanolamine?EA?in polyesters based on dimethyl terephthalate and ethylene glycol.,a series of comparative test on the conditions that may affect the properties of polymer are conducted.In comparison with the Sb₂O₃,the C-94 is selected as the catalyst;it is found that high vacuum degree can promote the polycondensation reaction in a positive direction;compared to the reaction temperatures of 230 ^oC,240 ^oC,255 ^oC and 260 ^oC,the polymer obtained by polycondensation at 250 ^oC has a better property;the dosage of catalyst will have an effect on the color and thermal property of polyester,therefore several dosages of catalyst is compared,and it is found that 50 ppm is appropriate.Adding an antioxidant and a flame retardant will make the color of polymer become lighter which is beneficial to the application,to this end,two kinds of additive with a dosage of 15 ppm are selected and put in the reaction system;in order to increase the molecular weight of polymer,a solid phase polycondensation is carried out to further remove small molecules.The polyester modified by the above conditions has a better thermo-oxidative stability,a lower melting point and more uniform molecular weight distribution,lighter color.After the experimental conditions mentioned above are chosen,four kinds of polyesters with an imide structure proportion of 20%,10%,5%and 0%respectively are prepared;and the thermal properties,optical properties and electrical properties are tested after the solid phase polycondensation.The effect of the amount of imide on the polyester is compared.It has been confirmed that the addition of the imide structure lowers the melting point of the modified polyester.As the proportion of the imide structure increases,the melting points increases,the water absorption rate decreases,and the processability and electrical insulation performance are better.