Study On The Preparation Of Anti-Hygrothermal Aging Functional Polyester Modified By Epoxy Group And CHDM

The optical biaxially oriented polyethylene terephthalate film(BOPET)has the advantages of high tensile strength,good optical properties,high elastic modulus,good toughness,and good thermal stability.However,the use of BOPET has been greatly restricted in the outdoor environment with high temperature and humidity due to the presence of ester groups in its molecular structures.Therefore,this paper presents the preparation of anti-hygrothermal aging functional polyester by adding glycidyl ester of of versatic acid(E10P)(as the blocking agent)and 1,4-Cyclohexanedimethanol(CHDM)(as the third monomer).The structure of the copolyester was characterized by 1H NMR.The thermal properties of the modified polyester were analyzed by differential scanning calorimetry(DSC)and thermogravimetric analyzer(TGA).The resistance to heat and weat aging of the modified polyesters was characterized by intrinsic viscosity and carboxyl-terminated changes.The crystallization properties of the modified polyesters were characterized by X-ray diffraction(XRD)and polarizing optical microscope(POM).The non-isothermal crystallization kinetics of the modified polyesters was calculated using the Jeziorny method,and the rheological properties of the modified polyesters were characterized using a rotary rheometer.The introduction of E10P and CHDM elements has little effect on the thermal properties and rheological properties of polyester,such as glass melting temperature,melting point and decomposition temperature.The results of XRD test and Jeziorny theory show that the addition of CHDM does not change the crystallization mode and spherulite morphology of PET.The addition of E10P makes the terminal structure of polyester complex,and the addition of CHDM destroys the regularity of the polyester molecular chains.Therefore,both of them can reduce the movement ability of the molecular chains and decrease the crystallization ability of the polyester,which is unfavorable to improving anti-hygrothermal aging ability of polyester.However,E10P can react with terminal carboxyl groups of polyester to effectively reduce the content of terminal carboxyl groups,inhibit the hydrolysis reaction of polyesters,and the introduction of the CHDM structural unit allows the polyester with the same molecular weight to contain less ester groups,which are beneficial to improve the anti-hygrothermal aging of the polyester.Therefore,the addition of E10P and CHDM has dual effect on the anti-hygrothermal aging ability of polyester.The experimental results show that when the 400 g TPA is added as raw material,it is necessary to add 20 m L E10P as a blocking agent after the polycondensation reaction in order to obtain the modified polyester with a carboxyl-terminated value of 0.The intrinsic viscosity of the modified polyester decreased by 17.3% at 18 hours aging.Further,when the addition amount of the third monomer CHDM is 4 mol%,the low carboxyl end groups copolyester has the best antihygrothermal aging ability.The intrinsic viscosity of copolyester is 0.618dl/g after 30 hours aging,which can satisfy the requirements of the film products for polyester raw materials.