Optimizing the preparation conditions of amphoteric polyacrylamide as a strength additive for recycled paper

Abstract Acrylamide, itaconic acid and methacryloyloxyethyl trimethylammonium chloride were used to synthesize a series of amphoteric polyacrylamides (AmPAM) by aqueous solution polymerization through varying the pH, the reaction time, the temperature and the composition. The polymers were characterized by molecular weight and added in a recycled pulp furnish to make sheets. Paper strength was highest with the polymer made at pH 7 and 70 °C for 6 h with a monomer ratio of 2:0.3:0.3 (AM:IA:DMC) with 0.6 % initiator (based on the total mass of monomers). The optimized polymer was characterized by thermal gravity analysis, Fourier transform infrared spectroscopy and was then added at various pH and dosage level to the pulp alone or in combination with PAC, to determine the optimum addition conditions. Strength increased significantly with AmPAM addition level and PAC dosage but pH had little effect. The treated fibers were characterized by Zeta potential and drainage measurements. SEM showed the presence of a polymer film that is believed to reinforce inter-fiber bonds in the paper.