Study On Grafted Starch With Anionic Hydrophilic Monomers

Starch is one of the most natural polysaccharides in nature.It has many kinds,abundant resources,good compatibility with environment and low price.Graft modified starch has both characteristics of natural polymer and synthetic polymer,and is widely used as high water absorption resin,water treatment agents,daily chemicals and other functional materials.The grafted copolymerization of cassava starch with acrylic acid?st-g-AA??cassava starch grafted acrylic acid/2-acrylanmido-2-methylpropanesulfonic acid?st-g-AA/AMPS?and cassava starch grafted acrylic acid/?-methacrylic acid?st-g-AA/MAA?were prepared by using N,N-methylene-bis-acrylamide?MBA?,tripropylene glycol diacrylate?TPGDA?and sodium silicate?Na₂SiO₃?as crosslinking agent,respectively,acrylic acid?AA?,2-acrylanmido-2-methylpropanesulfonic acid?AMPS?and?-methacrylic acid?MAA?as grafted monomers,potassium persulfate as initiator in an aqueous solution.The influence factors of grafting reaction were discussed and the properties of solution were analyzed.The st-g-AA was prepared.The effects of reaction time,reaction temperature,the ratio of monomer to starch,the amount of initiator,the type and amount of crosslinking agent on the graft copolymerization and the properties of the product were discussed,and the better formula and process conditions were shown as following:Starch content was8.1g,reaction time was 3h,reaction temperature was 45⁴7.5?,the molar ratio of monomer to starch was 7 or 8,initiator amount was 17×10^-4mol,crosslinking agent amount were MBA 3.0×10^-44 mol,TPGDA 3.0×10^-44 mol and Na₂SiO₃ 2.5×10^-43.0×10^-4mol,respectively.The viscosity and light transmittance of solution were better,the grafting percent?GP?and grafting efficiency?GE?were 79.19%and 80.81%.The solution viscosity of st-g-AA was stable at pH6¹0,but the salt tolerance was poor,the solution viscosity retention value was low when the salts containing Na⁺?K⁺?Ca²⁺?Mg²⁺were added.Keeping the ratio of monomer to starch at 7,a series of st-g-AA/AMPS was prepared by adding different amounts of AMPS strong acid-type anionic monomers,and the effects of the amount of AMPS on the graft copolymerization and the properties of the products were discussed.The experimental results showed that GP and GE were better when the dosage of AMPS was 30%of the total monomer molar,but the viscosity was better when the dosage of AMPS was 10%.The addition of AMPS improved the salt tolerance of the st-g-AA significantly,and the solution viscosity retention value was increased with the amount of AMPS increase when the salts containing Na⁺?K⁺?Ca²⁺?Mg²⁺were added.The retention value of the grafted products with TPGDA as crosslinking agent was markedly higher than those of MBA and Na₂SiO₃ as crosslinking agent.The st-g-AA/AMPS solution was stable and viscosity kept a high value at pH 7⁹.Keeping the molar ratio of monomer to starch at 7,a series of st-g-AA/MAA were prepared by adding different amounts of MAA.The experimental results showed that GP and GE were better when the content of MAA was 10%of the total monomer molar and the solution viscosity was better.The light transmittance of st-g-AA/MAA was higher than that of st-g-AA and st-g-AA/AMPS.The structure and properties were studied by ¹³C-NMR,FTIR,SEM,TGA and DSC.¹³C-NMR and FTIR showed that the graft copolymerization carried out successfully between cassava starch and monomers.The SEM showed that the surface morphologies of the grafted products had changed obviously.TGA and DSC showed better thermal property than that of cassava starch.