Study On The Synthesis Of Ultrahigh Molecular Weight And Low Molecular Weight Polyvinyl Alcohol

In this paper,ethylene acetate(VAc)was used as raw material and water as solvent to prepare ultra-high molecular weight polyvinyl acetate.The effects of different initiator types,initiator concentration,monomer concentration,temperature and time on the degree of polymerization of polyvinyl acetate were studied.The results showed that the optimum conditions were as follows:the temperature was 25 ?,the molar ratio of initiator to monomer was 1:3000,the mass fraction of monomer was 25%with potassium persulfate-sodium bisulfite as initiator,The reaction time was 8 hours to obtain polyvinyl acetate having a molecular weight of at most 786700.And further,we eluted it with methanol and sodium hydroxide to obtain polyvinyl alcohol.The polyvinyl alcohol was characterized by infrared spectroscopy(IR),nuclear magnetic resonance(NMR),gel permeation chromatography(GPC),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA),mechanical properties.The results show that the thermal stability of the obtained polyvinyl alcohol is better,about 3%weight loss at 200 ?,meet the heat treatment requirements,crystal melting temperature of 206 ?,high hardness,less prone to deformation.The synthesis of low degree of polyvinyl acetate was studied by using vinyl acetate as raw material,azobisisobutyronitrile(AIBN)as initiator and methanol as solvent.The effects of different initiator concentration,monomer concentration,time and temperature on the polymerization degree were investigated.The results showed that the optimum conditions were as follows:the molar ratio of initiator to monomer was 1:50,the volume ratio of monomer and solvent was 1:1,the reaction temperature was 65 ?,the reaction time was 3h,the lowest molecular weight was 21200 Polyvinyl acetate.And the alcohol is subjected to alcoholysis to obtain polyvinyl alcohol.The structural characterization and performance analysis were carried out by the above test method:the weight loss was 2.8%under 200 ?,the thermal stability was better;the elongation at break was much higher than that on the market,and its toughness was very good.