Development of poplar Kraft pulp strengths with cellulose nano fiber of rice straw

This study was carried out to make cellulose nanofiber reinforced Kraft liner paper from rice straw. In this regard, P.deltoides clone 69-55 as a fast growth and high yield biomass species was selected for pulp production. Variable factors of Kraft pulping process including sulfidity, active alkali, temperature and time were applied in three levels and liquor to wood ratio of 4:1. Optimum conditions of Kraft cooking were found as 23% sulfidity, 18% active alkali, 170 °C, and 180 min. cooking temperature and time, respectively. The pulping yield and kappa number of control pulp were measured as 53.94% and 17.2, respectively. Then, the pulp was refined to achieve freeness degree of 333 ml.CSF. Nano-cellulose fiber of rice straw was added to improve the strength of control kraft pulp. The nanofibers at 5, 10 and 15% loadings were mixed with pulp suspension and 60 g/m2 handsheets were manufactured by means of a laboratory handsheet maker. It was found that all the strength characteristics of prepared papers were improved by addition of nanofibers in different levels. Tensile, burst, and tear indices increased up to 26.31%, 20.08%, and 10.07%, respectively by addition of 15% cellulose nanofibers to the control pulp suspension. Moreover, bending stiffness and RCT improved to 24.48%, and 52.38%, respectively. The overall results indicated that incorporation of cellulose nanofibers had a positive effect on kraft liner pulp produced from P.deltoides.