The Synthesis And Properties Of Poly (Trimethylene Terephthalate) With High Intrinsic Viscosity

The poly(trimethylene terephthalate)(PTT)is an important thermoplastic polyester which has excellent elastic recovery,easy dyeing,outstanding stain resistance and chemical resistance.PTT fibers can be widely used in carpet,nonwoven,lingerie,swimsuit and high grade clothing.PTT can also be used as an engineering plastic applied in electronics/electrical automobiles,furniture and other fields.However the technology of producing PTT independently is not mature in domestic.This thesis focused on synthesis of high intrinsic viscosity PTT([?]? 0.90 dL/g)by direct esterification through one-step method.A series of PTTs with different intrinsic viscosities ranging from 0.21 dL/g to 1.06 dL/g were synthesized by polycondensation reaction.The structure and molecular weights of synthesized PTTs were characterized by FTIR and Ubbelohde viscometer.The effects of polycondensation reaction temperature,polycondensation reaction time,agitator speed and the vacuum degree on the intrinsic viscosity of PTT were studied carefully.The contents of carboxyl end group of PTTs were measured by titration method.It was found that the contents of carboxyl end group of PTTs were less than 20 mol/106g for PTT samples with an intrinsic viscosity greater than 0.6 dL/g.The thermal behavior of PTT was explored by thermogravimetric analysis.The results revealed that 5%weight loss temperature of PTT with intrinsic viscosity of 0.98 dL/g were 351.8 ? to 393.3 ? in nitrogen atmosphere at heating rates of 5 K/min to 40 K/min.The DTG curves of PTTs showed a single weight-loss step while the peak temperatures were 382.1 ? to 425.3 ?.The thermal degradation activation energy calculated using Flynn-Wall-Ozawa method,Coats-Redfern method and Phadnis-Deshpande method were 183.67 kJ/mol,190.36 kJ/mol and 209.16 kJ/mol respectively.Combined with these three methods,the most probable mechanism of degradation process of PTT was R1(Phase boundary controlled reaction(one-dimensional movement))deceleration type.The thermal degradation of PTT in air showed two weight-loss steps while the 5%weight loss temperature was 372.4 ?.The thermal degradation of PTT in nitrogen showed only one weight-loss step while the 5%weight loss temperature was 372.4 ?.The molecular weight has less effect on the thermal stability of PTT.The 5%weight loss temperature of PTT with different molecular weight was 367.5 ? to 371.0 ? and the maximum weight loss temperature were 400.0 ± 0.5 ?.The isothermal and non-isothermal crystallization behaviors of PTT were investigated using polarized optical microscope.The effects of crystallization temperature and intrinsic viscosity on the crystal nucleus formation,the line growth rate and crystallization morphology of PTT spherulite were studied.Banded spherulite was observed at a fixed temperature ranging from 185 ? to 220 ?.The results indicated that the time of the nucleation of PTT increased with increasing intrinsic viscosity and crystallization temperature.The line growth rate decreased with increasing intrinsic viscosity and crystallization temperature.The line growth rates of PTT spherulites were greatly influenced by the intrinsic viscosity at low crystal temperature.The number of PTT spherulites decreased with increasing of crystallization temperature,and the size of PTT spherulites increased as the crystallization temperature increases.Banded spherulites were also observed during non-isothermal crystallization process and the interference color of banded spherulites of PTT changed regularly in cooling process from carmine and blue to green and yellow since the refractive index changed.