Synthesis、Structure And Performance Of Polylactic Acid And Polylactic Acid Alloy

In this work, using the bulk polymerization to prepare biodegradable material polylactic acid, meanwhile synthesis of high molecular weight polylactic acid and polylacticacid alloy by chain extension and reaction with the second component polymer blending, designed to improve the mechanical properties of polylactic acid, and to improve its brittleness and a hydrophilic, high molecular weight polylactic acid and polylactic acid copolymers were successfully prepared to base on the research of the synthesis process.Poly (L-lactic acide) of high molecular weight was synthesized by using lactide ring-opening method with stannous octoate as catalyst. The influence of the reaction temperature, reaction time and amount of catalyst on the molecular weight of the synthesized polylactic acid investigated. The weight-average molecular weight of poly(lactic acide) could reach up to21.9X104g/mol by GPC measurement Both FT-IR and optical rotation verified that the PLA synthesized was Poly(L-lactic acid)(PLLA). DSC and XRD tests proved that the PLLA was a crystalline material with melting-point at170℃and mixed α’-and α-crystal phases. The tensile test showed that PLLA with high molecular weight had improved mechanical properties.Higher molecular weight of polylactic acide was prepared by using HDI chain extending method with the low molecular weight as prepolymer. The influence of the HDI amount、time of the chain extender and the different molecular weight of prepolymer on production. The weight-average molecular weight could reach up to20.3X104g/mol by GPC measurement. Both FT-IR and1H-NMR tests showed that the production still was poly(lactic acid), and the optically active characterized that the product was PLLA. DSC test showed that the Tg、Tm and the degree crystallinity of productions decreased. The XRD result indicated that the crystalline of product changed from mixed α’-and α-crystal phases to α-crystal phases. L-lactide was initiated by PEO as initiator and the stannous octoate as catalyst. The influence of feed ratio(the mass ratio of PEO and L-LA) on the PLLA/PEO copolymer. The weight-average molecular weight of PLLA/PEO copolymer could reach up to11.3X104g/mol by GPC. FT-IR and XRD tests proved successful synthesis of PLLA/PEO copolymer, optically active characterization of the copolymer still had the optically active. DSC test displayed that copolymers still had crystalline properties, Tm of PLLA and PEO segments of copolymer all decreased. The hydrophilicity test results showed that copolymerization with PEO improved the hydrophilicity of PLLA. The tensile property results showed copolymerization with PEO didn’t improve the brittleness of PLLA.The PLLA/IR alloy was successfully synthesed by L-lactide ring-opening with stannous octoate as catalyst in toluene solution of IR. The weight-average molecular weight of PLLA was4.9X104g/mol and weght-average molecular weight was183.9X104g/mol by GPC. BothFT-IR and’H-NMR tests showed that with the increase of the feed ratio, alloy appeared cis1,4structure absorption peaks of IR, and gradually increase. DSC result illustrated the PLLA/IR alloy still had crystallinity, with increasing content of IR, PLLA/IR alloy crystallization performance decreased.The PLLA/POE alloy was synthesed by L-lactide ring-opening with stannous octoate as catalyst in toluene solution of POE. Both GPC and FT-IR tests showed the products didn’t contain the POE component.