Synthesis Of Bio-based Polyester PBT,PTT And PBTS With Organic Guanidine Composite Catalytic System

The energy and environmental problems caused by petroleum-based polymer materials have aroused widespread concern in society.The development and application of bio-based polyester materials is the most important way to solve this problem.Poly butylene terephthalate(PBT)and poly trimethylene terephthalate(PTT),as a new generation of bio-based polyester materials,have excellent mechanical properties and processing properties,and have great application prospects.At present,catalysts used to synthesize PBT and PTT are mainly metal catalysts(such as antimony trioxide Sb2O3,tetrabutoxy titanium TBOT,etc.),and the amount is large,which inevitably causes a series of environmental problems.Therefore,research and development of green environmentally-friendly catalyst are both important in industrial development and ecological environment protection.At the same time,the application field of PBT and PTT is limited by its poor flexibility.Poly(butylene terephthalate-co-butylene sebacate)(PBTS)introduces long carbon chain fatty acid units on the basis of PBT,which enhances the flexibility and improves the degradation properties of the material.The development of such materials has important practical value and environmental significance.(1)PBT(Mw=7.85×104 Da,PDI=1.58,Tm=222.54?)was synthesized via melt polycondensation(MP)catalyzed with organic guanidine composite catalytic system.The structure of the polymerization product was characterized by 1H-NMR.The results showed that the molar ratio of the repeating unit TA and BDO in the synthesized PBT molecule was 1:1,which proved that the structure of the synthesized material conformed to the molecular structure of PBT.The effect of process conditions on the formation rate of by-product THF was investigated.The results showed that the formation rate of by-product THF during the synthesis of PBT by biomass organic guanidine catalyst was only 4.5%when the esterification temperature was 210? and the acid-to-alcohol ratio was 1.0:1.3,far below the lowest value reported in the literatureThe TGA(Thermo gravimetric analysis)analysis showed that the thermal degradation temperature of PBT synthesized by the organic ruthenium catalyst system was 375?,which was 17? higher than that of TBOT.Tensile properties test showed that the tensile strength TS=41.7 MPa and the elongation at break BE=52.4%of PBT synthesized by organic ruthenium composite catalyst system,which was superior to the PBT synthesized by TBOT(TS=36.9 MPa,BE=45.7%).(2)PTT with high molecular weight(Mw=0.93-1.08×105 Da)and narrow polydispersity(PDI=1.63?1.72)was synthesized via melt and melt-solid polycondensation(MP-SSP)catalyzed by biomass organic guanidine catalyst for the first time.The structure of the polymerization product was characterized by 1H-NMR.The results showed that the molar ratio of the repeating unit TA and PDO in the synthesized PTT molecule was 1:1,which proved that the structure of the synthesized material conformed to the molecular structure of PTT.The effect of acid-alcohol ratio on the properties of synthesized PTT was investigated.The results showed that the product with high molecular weight(Mw=10.14×104 Da),narrow polydispersity(PDI=1.70),was synthesized at the acid-alcohol ratio of 1.0:1.3 and at the esterification time of 4.5 h,the melt polycondensation time of 5 h and the solid phase polycondensation time of 15 h.(3)PBTS with high molecular weight(Mw=7.27?8.13×104 Da)and narrow polydispersity(PDI=1.63?1.72)was synthesized via melt polycondensation(MP)catalyzed by biomass organic guanidine catalyst for the first time.The PBTS copolymers with different molar percentages(10/90?90/10)of SeA/TA were synthesized by using biomass organic guanidine catalyst.Characterization by 1H-NMR showed that when the molar ratio of SeA to TA was added to the synthesized copolymer PBTS in a certain ratio(40/60,50/50,60/40),the fatty acid unit(SeA)to the aromatic unit(TA)(41.9/58.1,48.4/51.6,59.3/40.7)in the synthesized copolymer is almost the same as the actual charge ratio.It prove that the designed molar ratio of PBTS was synthesized.The thermodynamic properties of the synthesized copolymer PBTS were characterized by DSC(Differential scanning calorimetry)and TGA(Thermo gravimetric analysis).The results show that as the content of SeA increases,the melting point(Tm)of the copolymer decreases firstly and then increases.When the SeA content is 60%,the melting point is the lowest at 47.43?.The increase in the molar percentage of SeA enhanced the thermal degradation performance of the copolyester.Through the test of the tensile properties of the copolymer,the tensile strength of the copolyester firstly weakened and then increased with the increase of SeA,and the elongation at break increased firstly and then decreased.When the molar content of SeA is 60%,the elongation at break reaches the maximum,which is 1138.80%.Continue to increase SeA,the elongation at break of the copolyester will decrease until it drops to B=469.49%,but its flexibility is still better than PBT.