Synthesis, characterization and properties of polyacrylamide-starch composites

Polyacrylamide-starch composite was prepared by polymerization of maize or rice starch with acrylamide (Aam) using potassium permangante/citric acid initiation system. Major factors affecting the polymerization reaction were studied with a view to discover appropriate conditions for preparation of the composite. Results obtained imply that the total conversion (monomer converted to homopolymer and graft) increases by increasing concentrations of potassium permanganate from 0.5-0.20%, citric acid from 0.1-0.15 and acrylamide from 10-30% ows. Polymerization can easily be carried out at 40 degrees C for 6 min at pH 4 using a material to liquor ratio 1:25 under a stirring rate of 350 rpm. The results further imply (a) that the apparent viscosity of the composite increases by increasing Aam concentration irrespective of the rate of shear, (b) that for 30% Aam concentration the composite consists of 77.7% starch and 22.3% polyacrylamide of which 10.4% are grafted, (c) that the sizeability of polyacrylamide-starch composites is much better than that of native starches, and (d) that the kind of starch not only determines the total conversion but also the composition of the composite.