Synthesis Of Environmentally-friendly PBS And PBAT With Organic Guanidine Catalysts

In recent years,with the increasingly aggravation of white pollution caused by the blind production and abuse of the disposable petroleum-based plastics,the development and utilization of environmentally-friendly and biodegradable polymers based on renewable resources has aroused growing concern.Poly(butylene succinate)(PBS)possesses excellent biodegradability and controllable biodegradation velocity,which can be applied for plastics and films.While Poly(butylene adipate-co-terephthalate)(PBAT)is a novel kind of aromatic and aliphatic biodegradable polyesters,which possess good thermal stabilities and mechanical properties.Therefore,the study and application on the synthesis of PBS and PBAT has aroused growing concern in biodegradable polymer science.In this thesis,PBS with high molecular weight and narrow polydispersity was synthesized via melt(MP)and melt-solid state polycondensation(MP-SSP)catalyzed by organic guanidine for the first time;PBAT with high molecular weight,narrow polydispersity and proportion of BA/BT ranged from 45/55 to 30/70 was synthesized via melt-solid state polycondensation(MP-SSP).The thermodynamic properties and mechanical properties of the product polymers were characterized.(1)PBS with high molecular weight(Mw 1.71×105 Da)and narrow polydispersity(PDI 1.72)was synthesized using biogenic guanidine BG1 as catalyst via MP.The Mw of PBS is superior to that reported in the literatures,PBS with Mw 1.18×105 Da was successfully synthesized via SSP,which shortens the reaction time,improves the quality of the product polymer(melt-point temperature Tm 116 ℃,white snow)and simplifies the process.The characterization of the polymer structure by 1H-NMR indicated that the molar ratios of butylene and succinate in PBS polyester was 1.0:1.0.The characteristic results of DSC on product PBS with Mw 1.71 ×105 Da syntheized by MP showed that the crystalline-point temperature Tc was 74.16℃ the the enthalpy of fusion ΔHm was 69.57 J/g,the crystallinitie Xc were 63.07%and the Tm was 116.32℃ respectively.The characteristic results of DSC on product PBS with Mw 1.71×105 Da syntheized by MP-SSP showed that the Tc was 94.79℃ theΔHm was 68.31 J/g,Xc was 61.93%and the Tm was 115.54℃ respectively.The analysis of TGA showed that the thermal weight loss of the product PBS started at 379.7℃,completelly thermally-decomposed at 428.8 ℃ and thermally-decomposed with maximum rate at 422.1 ℃(-20.82%/min).(2)Different BA/BT compositions of PBAT with high molecular weight and narrow polydispersity were successfully synthesized using biogenic guanidines as combined catalysts(BG1-BG2)via MP-SSP.While BA/BT=30/70,Mw 2.04×105 Da,PDI 1.83;BA/BT=40/60 Mw 1.57×105Da,PDI 1.93;BA/BT=45/55,Mw 1.03×105Da,PDI 1.69;BA/BT=50/50,Mw0.93×105 Da,PDI 1.92。The characterization of the polymer structure by 1H-NMR indicated that the molar ratios of BA to BT commoner in PBAT copolyester were about 45/55,40/60 or 30/70.The characteristic results of DSC showed that glass transition temperature Tg improves with the increasing of aromatic compositon,as well as the thermal stability.While BA/BT=45/55,the Tm was 168.3℃.BA/BT=40/60,the Tm was 190.1℃.BA/BT=30/70,the Tm was 204.5℃.The analysis of TGA showed that if BA/BT=45/55,the thermal weight loss of the product PBS started at 323℃,completelly thermally-decomposed at 454℃ and thermally-decomposed with maximum rate at 432℃.If BA/BT=40/60,the thermal weight loss of the product PBS started at 342℃,completelly thermally-decomposed at 452℃ and thermally-decomposed with maximum rate at 431℃.If BA/BT=30/70,the thermal weight loss of the product PBS started at 348℃,completelly thermally-decomposed at 451 ℃ and thermally-decomposed with maximum rate at 432℃.Compared with the traditional MP,MP-SSP emplied in this thesis has such advantages:lower reaction temperature,short reaction time,white snow product polymer and simlpe to be produced in factories,et al.