ARS | Publication request: Reactive Extrusion of Starch Polyacrylamide Graft Copolymers

Submitted to: Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: March 8, 2004
Publication Date: June 1, 2004
Citation: Willett, J.L., Finkenstadt, V.L. 2004. Reactive extrusion of starch polyacrylamide graft copolymers. {abstract} p. 44.

Technical Abstract: Starch-polyacrylamide graft copolymers were prepared using a corotating twin screw extruder. Three free radical initiators were investigated: ammonium persulfate (APS), ceric ammonium nitrate (CAN), and ferrous ammonium sulfate-dydrogen peroxide (FAS). Polyacrylamide (PAAm) homopolymer was extracted with an ethanol/water solvent. PAAm molecular weights were measured using gel permeation chromatography after removal of starch by enzyme hydrolysis. APS was an effective initiator, with conversions of monomer to polymer of 90% or greater. Conversions with FAS were slightly lower, between 80% and 90% in most cases. CAN gave little polymer with conversion of 15% or less. PAAm molecular weights of 500,000 and greater were obtained with APS, while FAS gave molecular weights in the range 75,000 to 350,000. CAN was not effective, as no significant amounts of high molecular weight PAAm were detected. Grafting efficiencies followed the trend in conversion, with APS giving the highest efficiencies (approximately 75%), followed by FAS (approximately 50%) and CAN (20%). The average number of anhydroglucose units between grafts increased as the initiator concentration decreased for APS and FAS, and decreased slightly as the monomer/starch feed ratio increased. APS gave fewer PAAm grafts of higher molecular weight than FAS. Water absorbencies at pH 7.5 were measured after saponification of approximately 45% of the PAAm to carboxylate ions. Absorbencies were in the range of 100 g/g to 250 g/g depending on starch type and graft content.