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Study on Synthesis of Poly(L-lactic Acid) Via Direct Melt Polycondesation

Author: WangMeiLing
Tutor: LiFuSheng
School: Tianjin University
Course: Chemical processes
Keywords: Lactic acid Polylactic acid Biodegradable materials Direct condensation polymerization Prepolymer Melt polycondensation SnCl2 · 2H2O Sulfosalicylic acid
CLC: TQ323.4
Type: Master's thesis
Year: 2009
Downloads: 44
Quote: 0
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Abstract


Universal application of plastic on the environment caused serious pollution problems , and non-renewable petroleum resources . In this situation , the polylactic acid has aroused widespread concern . Polylactic acid (PLLA) is a completely degraded , the aliphatic polyester-based polymer material that is environmentally friendly , it is obtained from renewable raw material preparation , having a biodegradability and excellent mechanical properties . Polylactic acid can be used to replace now use some common plastics prepared by petrochemical products , reduce dependence on oil resources , but also reduce the pollution problems caused by waste plastic . There are two main ways polylactic acid by lactic acid synthesis : ring-opening polymerization and direct polycondensation method . Ring-opening polymerization route is long and complex process , leading to the high price of polylactic acid , it is difficult to compete General Plastics . The direct polycondensation law monomer conversion rate, the process is simple , low production cost , but the lower the molecular weight of the resulting polymer , how to increase the molecular weight of the polymer product is the key to the process . This paper studies the direct melt polymerization of polylactic acid synthesis process . Prepolymerization using lactic acid is dehydrated , the melt polycondensation of the two-step method to prepare polylactic acid . The operating conditions and the oligomers of lactic acid is dehydrated prepolymerized further melt polymerization process conditions . The study determined the lactic acid is dehydrated prepolymerized to give a degree of polymerization of the oligomer reaction conditions of about 8 : 2h before the reaction temperature was 150 ° C , the pressure was gradually reduced from atmospheric to 30mmHg , and then at 150 ℃, 30mmHg kept 4h , then the temperature was raised to 160 ℃, the pressure was lowered to 20mmHg, maintaining 2H . The oligomer obtained in melt polymerization, investigated the influence of a variety of catalytic systems on the polymer molecular weight , and the effects of various process conditions for the polycondensation reaction . Found that stannous chloride dihydrate ( SnCl2 · 2H2O ) / acid catalytic effect better optimum amount of 0.3 mol% (1:1 ) , the optimal reaction conditions : polymerization temperature of 180 ° C , the final pressure 1mmHg The polymerization time was 15h. And by differential scanning calorimetry Yee ( DSC ) , Fourier transform infrared spectroscopy ( FT - TR) , gel permeation chromatography (GPC) product characterization .

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CLC: > Industrial Technology > Chemical Industry > Synthetic resins and plastics industry > Polycondensation resin and plastic > Polyester resins and plastic materials
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