Synthesis And Characterization Of Poly(butylene Adipate-co-Terephthalate)

Poly?butylene adipate-co-terephthalate??PBAT?has excellent degradation properties and mechanical properties,which ultimately can be converted to carbon dioxide and water,over a span of time.PBAT has a good application prospect in the field of biodegradable films,disposable packaging materials and medical materials.In this research,In this paper,PBAT was prepared by direct melt polymerization using terephthalic acid?PTA?,adipic acid?AA?,and 1,4-butanediol?BDO?as raw materials.The PBAT was prepared by a direct melt polymerization according to a molar ratio of n?BDO?:n?PTA+AA?=1.4;n?PTA?:n?AA?=1.High molecular weight PBAT was prepared by adjusting the reaction conditions.First use of triphenyl phosphite?TPPi?for chain extension of PBAT without changing its chain structure.A series of testing instruments were used to study the chemical structure,terminal carboxyl,intrinsic viscosity,molecular weight and its distribution,molecular chain structure,thermal properties,crystal structure,mechanical properties,melt flow rate and hydrophilicity of PBAT,respectively.The effect of polycondensation temperature on PBAT was researched.The results showed that PBAT with hydrophilicity and narrow molecular weight distribution was prepared successfully.With the increase of polycondensation temperature,the content of terminal carboxyl group of PBAT first decreased and then increased;intrinsic viscosity,weight average molecular weight?M_w?,elongation at break and tensile strength first increased and then decreased.At the polycondensation temperature of 260?,weight average molecular weight of PBAT was as high as 21.69×10⁴ g/mol,and the elongation at break and tensile strength were as high as 1420.51%and 26.70 MPa,respectively.Therefore,260? was the best polycondensation temperature.The influence of catalyst type and heat stabilizer on PBAT were researched.The results showed that the PBAT was prepared under the conditions of a composite catalyst of tetrabutylorthotitanate?TBOT?and antimony trioxide?Sb₂O₃?.Its weight average molecular weight,color,and mechanical properties were not only superior to a single TBOT catalyst but also superior to TBOT/stannous octoate?Sn?Oct?₂?composite catalyst.Triphenyl phosphate?TPP?inhibited the thermal degradation of PBAT copolyester effectively.PBAT with a weight-average molecular weight as high as 21.69×10⁴ g/mol,milky white,elongation at break of 1420.51%,tensile strength of 26.70 MPa was prepared according to the condition of the TBOT/Sb₂O₃ composite catalyst.The effect of Sb₂O₃ content on PBAT was further studied.The results showed that with the increased of Sb₂O₃ addition,the content of terminal carboxyl group decreased first and then increased,the weight average molecular weight?M_w?first increased and then decreased.With the increase of the weight average molecular weight,the linear molecular chains of PBAT changed from random rods to tight spherical structures.Melt flow rate was affected by the weight average molecular weight and shows a tendency to decreased first and then increased,and the breaking strength,elongation at break and contact angle first increased and then decreased;The crystal structure was consistent with the crystal structure of poly?butylene terephthalate??PBT?.When the amount of Sb₂O₃ added was 0.10 mol%,the quality of PBAT was the best,the M_w was 24.00×10⁴ g/mol and the melt flow rate?MFR?was 15.63 g/10min,elongation at break up to 1525.66%,and tensile strength up to 25.19 MPa.The effects of processing temperature and TPPi addition on PBAT were studied.The results showed that at 170? and 190?,the molecular weight of PBAT increased with the increase in the amount of TPPi added;210?,due to thermal degradation and side reactions in the reaction,the molecular weight of PBAT increased first and then decreased;TPPi made the molecular weight components of PBAT more uniform and did not change its chain structure.At each processing temperature,with the increase in the amount of TPPi added,due to the effect of chain extension and plasticization of small molecule by-products,the elongation at break and fracture strength of PBAT increased first and then decreased;the melt flow rate first decreased and then increased.190?,TPPi 3.0 wt%was the best reaction conditions,the tensile strength and elongation at break of PBAT up to 35.79 MPa and2119.19%,respectively.The melt flow rate was 10.60 g/10min,which is twice as low as the original.