Technologic Research Of Synthesize Biodegradable Material Polylactic Acid And Modification

Polylactic acid(PLA)is a new polymer material for the synthesis of natural materials,and also a new form of plastic.Because of its complete degradation, therefore,the PLA is widely used in medical,packaging,fiber,and other fields.The focus of application is medical areas,involving drug microspheres carrier, anti-mucosa,biological catheter,orthopaedic implants,bone surgery devices,drug compound polymer stent,artificial bone materials and so on.The paper's contents mainly focus on the research of synthesis technology of traditional polylactic acid and microwave radiation synthesis method.And modify the character of polylactic acid in the further process,improving its hydrophilic performance through introducing polyethylene glycol(PEG)in the polylactic acid chain.The main research results are as follows:Synthesize intermediate product-lactide,using lactic acid as raw material.The effects of temperature,time,and catalyst were discussed by orthogonal experimentation and the optimum condition is as follow:the mass ratio of SnCl₂·2H₂O and lactic acid is 0.25;p-toluenesulfonic acid and lactic acid is 0.75,the reaction time is four hours under 150℃.In the late of the reaction process,adding 30ml n-octanol,the lactide yields reach 43.3%.Lactide which was made in our lab is as materials to synthesize polylactic acid through conventional methods of synthesis.The effects of temperature,time, catalyst were discussed by orthogonal experimentation and the optimum condition is: the mass ratio of SnCl₂·2H₂O and lactide is 0.001,reaction time is 20 hours under 180℃.The molecular weight of the polylactic acid products was 14.1×10⁴ which was determined by viscosimetry.Lactide which was made in our lab is as materials to synthesize polylactic acid through microwave synthesis.The effects of temperature,time,catalyst and microwave power were discussed by orthogonal experimentation and the optimum condition is:the mass ratio of SnCl₂·2H₂O and lactide is 0.001,the reaction time is 60 minutes under 180℃,microwave power is 500W.The molecular weight of the polylactic acid products was 4.5×10⁴ which was determined by viscosimetry.Synthesize the co-polymer-PLA-PEG,using the lactide and PEG as monomer and SnCl₂·2H₂O as catalyst.Research the effects of reaction time,temperature, molecular weight of PEG and the ratio of lactide and PEG to the molecular of co-polymer.The results show:we can get higher molecular weight co-polymer-PLA-PEG,adding 1‰catalyst-SnCl₂·2H₂O,reaction time 10h,temperature 180℃in the reaction process of lactide and PEG.If cutting down the content of PEG and increasing the length of PEG segmer,we could manufacture higher molecular weight co-polymer.We found that the hydrophilic performance of the polymer was obviously improved and the Tg was reduced through introducing polyethylene glycol(PEG)in the polylactic acid chain through contact angle and DSC analysis.