Impact of cationic polyvinyl alcohol on properties of papers made from two different pulps

Abstract

In this study, the effect of cationic polyvinyl alcohol (CPVA), with charge density of 0.4 meq/g, on the properties of papers made from a bleached softwood sulfite pulp and from an unbleached straw pulp was systematically investigated. The CPVA adsorbed more on the unbleached straw pulp than on the bleached sulfite pulp. Increasing the dosage of CP VA significantly increased the strength properties of the papers made from the unrefined bleached sulfite pulp, but produced only a limited increase in the strength properties of the papers made from the unrefined unbleached straw pulp. Refining was more effective at changing the characteristics of fibres and papers made from the bleached sulfite pulp than those from the unbleached straw pulp, regardless of the CPVA application. At the same sheet density, applying CPVA increased the tensile index of papers made from the unbleached straw pulp more significantly than that of papers made from the bleached sulfite pulp. Over the CPVA dosage range investigated, applying CPVA was more effective than refining at enhancing the strength properties of the papers made from the unbleached straw pulp. In contrast, refining was more effective than applying CPVA at enhancing the strength properties of the papers made from the bleached sulfite pulp. The effect of CPVA on the structural and optical properties of the papers was comprehensively assessed.