Preparation And Study Of Polytrimethylene Terephthalate

Polytrimethylene terephthalate(PTT) is a high-capacity thermoplastic polyester material. PTT have the mechanical strength, tenacity, heat resistance of PET and the processing advantages of PBT. PTT fibers possess higher drawing recovery and lower modulus than PET fibers and PET fibers. PTT fibers also have good workability, easy dyeing and fluffiness of PA fibers. High molecular weight PTT has great application prospect for fiber and engineering plastic, but the preparation and production technology in domestic is not mature enough.Orthogonal analysis has been adopted to investigate the effects of molar ratio of 1,3-PDO/TPA, catalyst constration, prepoly condensation temperature and prepolycondensation time on the intrinsic viscosity of PTT and to optimize the polymerization procedures. High molecular weight PTT with an intrinsic viscosity of 1.0 dL/g can be obtained via solid state polymerization.A series of Polytrimethylene terephthalate-co-dimethylene terephthalate(PTDT) copolyesters were synthesized based on PTA,1,3-PDO and 1,2-PDO. The nonisothermal crystallization behaviors of PTDT copolyesters were investigated using DSC. The results showed that for a chosen cooling rate, the crystallization peak temperature shifted to lower temperature as the content of 1,2-PDO segments increased. Jeziorny’s, and Mo’s models were employed to describe the non-isothermal crystallization kinetics of the PTDT samples. The Mo’s model was able to describe the nonisothermal crystallization kinetics of PTDT copolyesters satisfactorily. The results obtained from Mo’s model showed that the crystallization rate of PTDT copolyesters decreased as the content of 1,2-PDO segments increased. Jeziorny’s model revealed that the crystallization constant Zc increased with the cooling rate, whereas the reciprocal value of half-crystallization time was shortened, indicating that the crystallization rate increased with the cooling rate. Moreover, for a chosen cooling rate, the crystallization constant Zc decreased as the content of 1,2-PDO segments increased, whereas the reciprocal value of half-crystallization time was prolonged, indicating that the crystallization rate decreased as the content of 1,2-PDO segments increased. The results obtained from Jeziorny’s model was in accordance with the results obtained from Mo’s model.The plots of sample PTDT-1, PTDT-2, PTDT-3 and PTDT-4 obtained from Jeziorny’s model and Ozawa’s model showed poor linearity, however, the nonisothermal crystallization kinetics of PTDT-5 were well described by Jeziorny’s model and Ozawa’s model.The spherulitic morphology of the PTDT copolyesters were observed by POM. The results showed that the spherulitic morphology of sample PTDT-5 maintained intact and clear. The impingement of the spherulite had not happened. While the impingement of the spherulites of sample PTDT-1, PTDT-2, PTDT-3, PTDT-4 and the distinct grain boundary between spherulites could be observed. The deviation from the Avrami and Ozawa equation can be attributed to spatial constraints of spherulitic growth, which was proposed by Tobin and Sajkiewicz.The crystallization activation energies were determined from the Kissinger method. The results showed that the crystallization activation energy increased as the content of 1,2-PDO segments increased, indicating the incorporation of 1,2-PDO makes it more difficult for the PTDT copolyesters to crystallize.The thermal stability analysis of PTDT copolyesters was performed on TGA. Thermal degradation parameters of PTDT copolyesters with different 1,2-PDO segments content were very close.