Study On The Applications Of Titannium-Based Composite Catalysts In Poly (Ethylene Terephthalate)(PET) Synthesis

Based on the study of the catalytic mechanism of Ti-based catalysts for PET,three new titanium-containing catalysts were synthesized by using the titanium glycolate,tetrabutyl titanate,or tetraethyl silicate and phenyl phosphoric acid as reactants.Then the effect of 3 new Ti-based catalysts and the addition time during the PET synthesis reaction on the structure and properties of the products were investigated in detail.Furthermore,the properties of resultant PET were also compared with that by Sb₂O₃.Finally,Finally,the optimum composite catalyst was obtained.The structure and physical properties of all obtained PET were characterized by colorimeter,gel permeation chromatography(GPC),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA),and Instron et al.In addition,the kinetics of polycondensation of PET was also studied by employing the optimum Ti-based catalyst.The results show that the L value and b value of PET synthesized by our titanium catalyst are higher than those of PET synthesized with Sb₂O₃,indicating that the PET product has a larger brightness but a yellowish color.There was no big change of the glass transition temperature(T_g),melting temperature(T_m),and cold crystallization temperature(T_cc).The thermal stability of the composites is slightly improved.By using the Ti-based catalyst that from tetrabutyl titanate,tetraethyl silicate and phenyl phosphoric acid,the intrinsic viscosity of PET obtained has been improved and their molecular weight is the highest with narrow distribution.The tensile strength and elongation of obtained PET also increased.In this work,the Ti-based catalyst by the reaction of tetrabutyl titanate,tetraethyl silicate and phenyl phosphonic acid was the optimum catalyst,which showed 17 times catalytic activity of that of Sb₂O₃,and the polymerization rate was significantly improved.