Effects of sodium hydroxide concentration on properties of pulp and paper derived from Sesbania grandiflora

Chlorine based bleaching is a treatment to brighten the pulp but it has adverse effects to the environment. In this research, sodium hydroxide acts as total chlorine free bleaching agent to bleach the pulp derived from Sesbania grandiflora, Turi. Turi is a straight log species and it is fast growing. These characteristics are needed in pulp and paper industry to meet the increasing demand of the paper. However, the research on Turi as a pulpwood is limited. This research aims to provide information of the effects of sodium hydroxide treatment on pulp and paper properties derived from Turi. The sodium hydroxide concentration used to bleach the kraft pulp derived from Turi was 0%, 3%, 6% and 9%. The physical, optical and mechanical properties of hansheets formed were tested according to TAPPI standard. The kappa number, brightness and mechanical properties were significantly affected by sodium hydroxide except the physical properties and opacity. The improved of brightness of handsheets was obtained with the increasing sodium hydroxide concentration. Folding endurance of handsheets was decreased with the increasing sodium hydroxide concentration. Both tensile index and tearing index were increased at 3% sodium hydroxide but decreased after 3% sodium hydroxide. In conclusion, 3% sodium hydroxide is the most optimum to bleach the pulp derived from Turi as it improves brightness and mechanical properties. Excessive usage of sodium hydroxide weakens mechanical properties of paper made from Turi pulp.