The Study Of The Graft Copolymerization Of Starch And AM In The Carbon Dioxide Medium

The copolymer of starch graft acrylamide （AM） is a class of commonly used polymerflocculant, there are many methods for the polymerization of these copolymers, but eachmethod has its shortcomings, so it is necessary to find a new method for high solid contentand green polymerization. This thesis studies the graft copolymerization of starch and AM inthe CO₂and super critical CO₂（SC-CO₂）, to provide a new way for the graft copolymerizationof starch and AM.Firstly, the polymerization of starch and AM in the CO₂is studied. Under the protectionof CO₂, the graft copolymer of starch and AM was prepared by solution polymerizationreaction with initiator system （ammonium persulfate/urea）. The effect of the reactiontemperature、reaction time、the mass ratio of materials and initiator content on graftingefficiency、grafting ratio、monomer conversion and characteristic viscosity is determined. Itcan be concluded when the mass ratio of starch and AM is1:1.5, initiator content is0.4%ofmonomer quality, reaction temperature is60℃and reaction time is4h; the grafting efficiencyand grafting ratio reach to the highest value, which is94.3%å’Œ135.8%, respectively.Meanwhile the monomer conversion is99.9%, and characteristic viscosity is951.0mL/g.Under optimized conditions, the solid content of graft copolymer is14.6%.Based on the studies of graft copolymerization of starch and AM in CO₂, thecopolymerization in SC-CO₂has been studied. In SC-CO₂, the copolymer reaction processused starch as substrate, AM as monomer, ammonium persulfate/urea as the initiator system,SC-CO₂as reaction medium has been carried out, and starch graft AM polymer flocculantwith high solid content is obtained. The effect of the reaction pressure、reaction time、reactiontemperature、the mass ratio of materials and initiator content on grafting ratio、graftingefficiency and monomer conversion is studied, and the following conclusions can be obtained:the best reaction condition is that the mass ratio of starch and AM is1:1.5, initiator content is0.4%of monomer quality, reaction pressure is20MPa, reaction temperature is60℃andreaction time is3h. Under these conditions the grafting ratio and grafting efficiency reach to the highest value,134.0%and93.7%, respectively, and monomer conversion is97.6%. Underoptimized conditions, the solid content of graft copolymer is40.0%. IR spectra also show thatthe products of starch and AM copolymers have been obtained. Compared with thepolymerization of starch and AM in the CO₂, the polymerization in SC-CO₂can obtain highersolid content graft copolymers, and shorten the reaction time.