APPLICATION OF AMPHOTERIC POLYACRYLAMIDE IN STRENGTH IMPROVEMENT OF PAPER SHEETS AND THE MECHANISM REVEALED BY QCM-D TECHNIQUE

摘要

Water-soluble amphoteric polyacrylamide(AmPAM)has been widely used in papermaking as an agent for flocculation,retention,filtration,and dry-strength improvement.In this investigation,an AmPAM sample with MW of 712k was used solely or combined with cationic starch in the strength improvement of paper sheets made from kraft hardwood fiber or recycled old corrugated container(OCC)fiber.The results showed that AmPAM was better than cationic starch as dry strength additive of paper,especially used for recycled fibers.When dosage at 1％(wt％to mass of oven dried pulp),AmPAM sample improved the breaking length of virgin hardwood kraft pulp by 25％,and improved that of OCC by 80％.And along with strength improvement,additional benefits,e.g.decreased conductivity of slurry,increased retention and decreased beating degree were obtained as well.In the adsorption part,its adsorption behaviors on silica but with varying medium pH were monitored by quartz crystal microbalance with dissipation(QCM-D)technique.The results revealed that the maximum adsorption of AmPAM occurs at medium pH close to its IEP.In sum,AmPAM is an efficient,multi-beneficial dry strength agent for paper making process,especially for low quality fibers,such as recycled fiber.