Chitosan as a dry strength agent for paper

The effect of chitosan on properties of handsheets made from bleached eucalypt pulp has been quantified. The conditions in this study covered acidic, neutral and alkaline. The chitosan dosages tested were 0%, 0.25%, 0.5% and 1% based on the mass of oven dry pulp. The results showed that chitosan addition up to 1 improved the mechanical properties of paper, but the rate of increase in strength properties was higher from 0 to 0.5% compared to 0.5 to 1% regardless of the furnish pH. Chitosan is a superior dry strength additive either in acidic or neutral condition, but it is less effective under alkaline conditions. The possible explanation of this observation is discussed. In general, it is concluded that chitosan has potential to be used as a dry strength additive in neutral, acidic or alkaline conditions depending on process requirements.