Synthesis And Characterization Of Polylactide/Silica Nano Composites

In this paper, polylactide/SiO2 composites was synthesized by indirect method. It included the synthesis of lactide, the purification of lactide, the polymerization of lactide and the composites's analysis and so on.First, D, L-lactide was prepared from D,L-lactic acid with zinc acetate as catalyst, crude yield was 86.6%. Effects of dehydration time and temperature of lactic acid, type and amount of catalysts on crude yield of lactide were studied. The samples were characterized by means of FT-IR and DSC. The results showded that the optimal conditions were as follows: atmospheric dehydration temperature was 125.0℃, amount of zinc acetate was1.7%, vacuum dehydration temperature was 150.0℃, depolymerizing temperature was 232.0℃. Ethanol was an appropriate solvent for recrystallization, with which the melting range of D,L-lactide was 125.8~127.4℃and the total yield of purified lactide increased to 55.1% after three recrystallizations.Then, hydroxyl groups were introduced on the silica nanoparticles by the complete hydrolysis of coupling agentγ-glycidochloropropyl methyl trimetho- xy silane(KH-560). Ring-opening polymerization of lactide was induced on the silica nanoparticles surface using aluminum isopropoxide[Al(OiPr)3]as catalyst in the solution of dimethyl benzene, polylactide/silica nano-composites was prepared by this method and characterized by means of FT-IR, DSC and SEM. The results showded that silica was highly dispersed into the polymer and were linked together polyactide through the chemical bond due to coupling agent. The results showded that the optimal polymerisation conditions were as follows: amount of catalyst was n(I)/n(M)= 1/400, polymerization temperature was 120.0℃, polymerization time was 8h, monomer concentration was 4.6mol/L, amount of silica was under 5%.