Abstract: Water-in-water type cationic polyacrylamide (CPAA) emulsion was synthesized through free-radical copolymerization of acrylamide and dimethyl diallyammonium chloride (DDAC).The impacts of application conditions,such as dosage of CPAA emulsion, reaction time, amount of aluminum sulfate, pH value of wood pulp and stirring speed on its reinforcing effect toward bleached wood-pulp were explored. As a result, compared to paper characteristics without CPAA emulsion, breaking length and tearing index of paper sheets of wood pulp were increased respectively by 28.7% and 12.4% at charge of CPAA emulsion 0.8% (on oven dry pulp), reaction time 10 min, pH value 7.0, dosage of aluminum sulfate 0.5% (on oven dry pulp) and stirring speed 150 r/min. The expected molecular structure of CPAA made in our lab was identified from its infrared spectrum. Its reinforcing mechanism toward bleached wood pulp was also explored elementarily by comparing photographs from environmental scanning electron microscopy (ESEM) between paper sheets with and without CPAA emulsion treatments.

Key words: cationic polyacrylamide emulsion, strengthening agent, wood pulp, ESEM