| In recent years,the increasingly environmental pollution caused by the blind production and abuse of the disposable petroleum-based plastics has aroused worldwild conceren.Developing and utilizing environmental-friendly biodegradable polymers to replace petroleum-based plastics is an effective way to solve this problem.Biodegradable polymers(such as poly(lactic acid)(PLA)and poly(butylene succinate)(PBS)and so on)have attracted great interest and attention.PLA has a hard texture and poor toughness and PBS has low impact resistance and melting point which limited their application areas.Poly(butyleneadipate-co-terephthalate)(PBAT)was developed to overcome the disadvantages of PBS.This copolymer greatly increased the mechanical and thermal properties.However,while the content of terephthalic acid is higher than 55%(TA/AA≥ 55/45),the polymer is difficult to degrade in the environment.To solve the problem,organic guanidine BGi catalyst for poly(Adipic acid-co-succinic acid-co-butylene terephthalate)(PBAST)synthesis was explored for the first time in this thesis.A biodegradable copolymer PLA-PBS was successfully synthesized with an organic guanidine catalyst for the first time.1.Different BA/BS/BT compositions of PBAST with high molecular weight(Mw 0.41 × 104Da)and narrow polydispersity(PDI 1.7～1.9)were successfully synthesized using biogenic guanidine catalyst BGi via MP-SSP.The thermomechanical properities,thermal stabilities of the product PBAST were characterized.1H-NMR characterization of the polymer structure indicated that the molar ratios of BA,BS to BT commer in PBAST copolyester were(50/5/45),(45/5/50),(40/5/55),(45/10/45),(40/10/50)or(35/10/55).The characteristic results of DSC showed that while the BS unit maintains a constant composition of 5 mol%,the melting pointing Tm improved from 162.45℃ to 179.77℃ with the increasing of aromatic composition;When the BS unit maintains a constant composition of 10 mol%,the Tm improved from 157.84℃ to177.41℃.The analysis of TGA showed that when the BS unit maintains a constant composition of 5 mol%,with the increasing of the molar amount of BT units in the polymer(45 mol%-55 mol%),the initial thermal degradation temperature Td,i and the complete thermal degradation temperature Td,e of the polymer changed from 326℃ to 363 ℃ and 450℃to 462℃,respectively;while the BS unit maintains a constant composition of 10 mol%,with the increasing of the molar amount of BT units in the polymer(45 mol%～55 mol%),the Td,i and the Td,e of the polymer changed from 315℃ to 345℃and 446℃ to 463℃,respectively.The Tm value of the polymer is higher than 300℃which proved the excellent thermal property of PBAST.Compared with the traditional synthesis by MP,MP-SSP method emplied in this thesis showed advantages of lower raction tenperature,short reaction time,snow white polymer and simple production technology,et al.2.Copolymer PLA-PBS was synthesized using biogenic guanidine BG2 as catalyst via MP:the molecular weight(Mw)of PBAST were 3.80 × 104 Da～8.55 × 104 Da and polydispersity were 1.6～1.8.1H-NMR characterization of the polemer structure indicated that the molar ratios of PLA and PBS in PLA-PBS copolymer was(10/90),(20/80),(30/70),(40/60),(50/50).Polymer tensile test showed that pure polylactic acid material has a tensile strength of 46.1 MPa and an elongation at break of 1.57%.The elongation at break of the polymer increased first and then decreased with the increasing of the molar content of PBS(10mol%～50mol%).When the molar content of PBS reached 30%,the elongation at break of the copolymer reached a maximum value of 106.61%.The results showed that with the increasing of PBS content,elongation at break of the copolymer increased significantly. |
