Submitted to: Journal of Applied Polymer Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/15/2004
Publication Date: 6/15/2004
Citation: Willett, J.L., Finkenstadt, V.L. 2004. Reactive extrusion of starch-polyacrylamide graft copolymers. Journal of Applied Polymer Science. p.336-339. Interpretive Summary: The production of new biobased materials from starch, a renewable resource derived from corn and other grains, often requires chemical modification to provide specific properties desired for end-use applications. New processes with reduced environmental impact are needed to modify starch. Reactive extrusion is a continuous process using equipment similar to that used for production of puffed food products. Chemical compounds known are initiators are needed for some types of starch modifications. We have demonstrated the effects of three different initiators on the properties of modified starches produced by reactive extrusion. Properties of the modified starches can be controlled by the choice of initiator and the amount used. Application of this technology may lead to new materials based on starch, with applications such as absorbent materials.
Technical Abstract: Starch-polyacrylamide graft copolymers were prepared by reactive extrusion using ammonium persulfate (APS), ceric ammonium nitrate (CAN), or ferrous ammonium sulfate-hydrogen peroxide (FAS/H2O2) as initiator. Initiator contents, measured as anhydroglucose units per initiator radical (AGU/I) ranged from 70 to 280 AGU/I for CAN and FAS, and 70 to 1140 for APS. CAN was not an effective initiator, giving low conversions, low graft content, low grafting efficiencies, and no detectable high molecular weight polyacrylamide (PAAm). FAS/H2O2 gave conversions of approximately 80%, graft efficiencies of approximately 50%, and PAAm molecular weights from 75,000 to 357,000 depending on initiator content and starch/acrylamide ratio. APS gave conversions exceeding 90% with graft efficiencies of approximately 75%. PAAm molecular weights with APS were 575,000 and greater. As the AGU/I ratio increased above 280 for APS, conversion and graft content decreased, while graft efficiency was essentially constant. Initiation with APS gave fewer PAAm grafts of higher molecular weight compared to FAS/H2O2.