Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/15/2003
Publication Date: 11/12/2003
Citation: Willett, J.L., Finkenstadt, V.L. 2003. Preparation of starch graft copolymers using reactive extrusion. 1st IUPAC International Conference on Bio-based Polymers. p. L41.
Technical Abstract: Graft copolymers of starch and polyacrylamide (PAAm) have been prepared by reactive extrusion using a 30 mm co-rotating twin screw extruder. Among the variables studied are acrylamide content, moisture content, and initiator type and amount. Typical residence times in the extruder were four minutes or less. For acrylamide: starch ratios less than 1, conversion of monomer to polymer typically exceeds 90 per cent when ammonium (APS) is used as the initiator. Grafting efficiencies of 70 per cent or greater were obtained with APS. PAAm molecular weights of several hundred thousand are typical. Ceric ammonium nitrate (CAN), commonly used as an initiator with starch, gave low conversions and grafting efficiencies. The redox initiator ferrous ammonium sulphate-hydrogen peroxide gave conversions and grafting efficiencies somewhat less than those with APS, but significantly greater than those with CAN. Monomer conversion and grafting efficiency were not significantly impacted as the anhydroglucose unit/initiator ratio increased from 70 to 280. At constant starch-acrylamide ratio, monomer conversion and grafting efficiency increased with decreasing moisture content. Monomer conversion and grafting efficiencies did not vary greatly when various starches were used as substrates for grafting. These results demonstrate that continuous reactive extrusion can be used to prepare starch graft copolymers with high reaction and grafting efficiencies.