关键词: 共聚酯, 异山梨醇, 钛系催化剂, 玻璃化转变温度

Abstract: In order to increase the glass transition temperature (T_g) of polyethylene terephthalate (PET) and broaden the application field of PET, poly (ethylene terephthalate-co-isosorbide terephthalate) (PEIT) was prepared by direct esterification with bio-based isosorbide (ISB) as the third monomer and self-made Ti-Al bimetallic coordination compound as catalyst.The structure and thermal properties of the copolyester were characterized by nuclear magnetic resonance, Fourier transform infrared spectrometer, differential scanning calorimeter, and thermogravimetric analyzer.The results show that the self-made catalyst has good catalytic activity for ISB. When adding less than 15% of ISB, the reaction rate can reach 90%, and the copolyester product with an intrinsic viscosity of about 0.65 dL/g can be quickly obtained. The intrinsic viscosity of the copolyester increased to about 1.20 dL/g after 1.5 h of melting post polycondensation, which indicates that the copolyester prepared by the titanium-based catalyst has strong chain growth ability during melt polycondensation. Increasing the proportion of ISB in the synthesis will reduce the intrinsic viscosity of the copolyester, but the crystallization temperature(T_c) of the copolyester will increase and the melting point(T_m) will decrease. There is a positive correlation between glass transition temperature (T_g) and the added ISB content. When the amount of ISB added reaches 20%, the T_g of the copolyester reaches 94.7 ℃, and the correlation calculation formula of T_g and ISB content is obtained by fitting.However, when the amount of ISB exceeds 15%, the polymer begins to transform into an amorphous polymer, but its thermal decomposition performance is not significantly affected.

Key words: copolyester, isosorbide, titanium catalyst, glass transition temperature