| In this work, the thermomechanical pulp of hardwood was pretreated with a NaOH/urea aqueous solution to increase paper strength. The effects of pulp concentration, alkali dosage, soaking time, and freezing time were evaluated through single factor experiments. The optimum conditions were found as the follows: pulp consistency of 15%, alkali dosage of 8%, soaking time of 15 min, and freezing time of 60 min (-10℃). Under these conditions, the paper tensile and burst index of treated pulp increased nearly 60%, and the bulk decreased, however, there was no significant effect on folding strength． |
