A Study On The Poly(Butylene Adipate-co-butylene Terephthalate) Copolyester

Poly (butylene adipate-co-butylene terephthalate) copolyester (PBAT) as a newbiodegradable copolyester has the advantages of both aromatic polyester and aliphaticpolyester, with good thermal properties, mechanical properties, biodegradability andmachinability. Therefore, PBAT has become the research hotspot of domestic and foreignindustry and academia. In this paper, using dimethyl terephthalate(DMT),1,4-butanediol(BD), adipic acid(AA) as raw materials and tetrabutylorthotitanate(TBOT), stannousoctoate(Sn(Oct)2) as composite catalyst, PBAT was synthesized via melt polycondensationmethod. Influence factor of the synthesis process condition was studied. Their intrinsicviscosity, chemical structure, crystal structure and thermal properties were investigated bymeans of Ubbelohde viscometer, FT-IR,1H NMR, XRD, DSC and TGA, and theirmechanical properties and hydrophily were measured through tensile test and contactangle measurement.Firstly, a series of PBAT copolyesters were synthesized under differentpolycondensation time. Studies of PBAT copolyesters with different polycondensation timeshowed that the maximum intrinsic viscosity of PBAT copolyester was0.1011dL/g underthe condition that n (DMT+AA): n (BD)=1.0:1.3, n (DMT): n (AA)=5:5and thepolycondensation time was65min. The DSC and TGA showed that the crystallizationtemperature, melt temperature and thermal weight loss were the highest respectively107.25℃，136.24℃and314.22℃. The tensile strength and elongation at break were13.4MPa and876%, and the contact angle was68.8°.Secondly, the influence on PBAT copolyesters from different adding ways of catalystTBOT was studied. The results showed that the intrinsic viscosity of PBAT obtained fromadding TBOT in phases was0.0075dL/g higher than which was obtained from addingpolymerization system by one time, and its thermal properties and mechanical propertieswere better.Finally, a series of PBAT copolyesters were synthesized with different n (DMT): n(AA). The analysis of FT-IR and1H NMR showed that the synthesized PBAT was randomstructure. The XRD tests showed that the PBAT coplyesters of different molar ratios hadthe same crystal structure which is the same as PBT homopolymer. The DSC showed thatwith increasing of BT contents, the crystallization temperature, crystallinity and melting temperature got higher, and appeared apparent double melting peak when the BT contentreach to80%. The TGA showed that the heat weight loss temperature of PBAT enhancedwith the increasing of the n (DMT): n (AA). The mechanical properties test indicated thatthe tensile strength was increased and the elongation at break was obviously decreased withincreasing of DMT content. The test of a series of contact angles on the surface of PBATcopolyesters showed that contact angle of PBAT copolyesters increased and its hydrophilydecreased slowly with the increasing of DMT.