Synthesis And Properties Of PET-co-PEA Flexible Copolyester

The rigid molecular structure of polyethylene terephthalate(PET) leads to its film products hard and poor tear properties, which limits their application. This paper presents a synthesis of a flexible polyester using copolymer modified method.The flexible polyester PET greatly improved flexibility, broaden the application of the polyester film, especially the application in the field of agricultural greenhouse film.In this paper, the PET-co-PEA flexible copolyester was synthesized by direct esterification adding polyethylene adipate(PEA) as modifying monomers.The fourier transform infrared(FTIR) spectroscopy was used to characterize the PET-co-PEA copolyester structure.The thermal properties of the PET-co-PEA copolyester was analysized using a differential scanning calorimeter(DSC) and thermogravimetric analyzer(TGA). The intrinsic viscosity and terminal carboxyl group was used to characterized PET-co-PEA copolyester hydrolysis resistance. The crystallizability of the PET-co-PEA copolyester was studied by polarizing microscope(POM). Using a melt indexer and rotary rheometer investigated PET-co-PEA flexible copolyester rheological properties. The results showed that P EA was successfully introduced into the copolyester and greatly improved supple and flow properties of PET. PEA does not affect the copolyester thermal stability and light transmission properties, but the glass transition temperature of the copolyester, th e melting point and the crystallinity decrease with increasing PEA content. At the same time, the higher content of PEA, the water degradation of copolyester is stronger. Crystalline has no effect on the hydrolysis of PET-co-PEA copolyester.The tensile and heat set of the PET-co-PEA flexible copolyester film was systematicly analysized. The effect of the stretching and heat-setting process on polyester shrinkage, crystallization, strength and optical properties were explored. The results showed that the tensile strength and the crystallinity of the strected PET-co-PEA flexible copolyester film increases. The melting point, thermal shrinkage and elongation decreased. The optimal heat setting temperature of maintaining the strength and elongation at break is 90 oC. The optical performance of PET-co-PEA films which had been stretched and heat-seted is constant at room temperature. The effects of PEA content on PET-coPEA flexible copolyester film strength, tear strength and the hydrophilic properties were studied using a universal tensile tester and static contact angle measurements. The results showed that the strength of the PET-co-PEA flexible polyester film is subsequently increased and then decreased with the content of PEA increasing. The introduction of PEA to the PET film solved the problem of stress concentration, and significantly improved tear properties of polyester films. The maximum tensile strength of the PET-co-PEA is 5.7 times of PET. Meanwhile PEA can increase PET-co-PEA copolyester water wetting properties. The mechanism was determinated based on the molecular structure, molecular orientation and crystallization aspect, of which the tensile strength of PET-coPEA copolyesters decreased after the first increased with PEA content increasing. The theory of molecular chain reversing and group transferring was proposed to explain the hydrophilic enhancement phenomenon of PET-co-PEA with the increasing content of PEA.