The Use of Kraft Lignin in Fiberboard Production

In this research, the effect of kraft lignin content, temperature and time of hot press on some physical and mechanical properties of wet process hardboard (S IS) made from mixed fibers of various species of Iran Fiber Company was studied. The values of 1) Kraft lignin, .precipitated from Kraft black liquor, at three levels of 0, 5 and 10 percent (based on ovendried weight), 2) press temperature at two levels of 190 and 200 degrees centigrade and 3) press time at two levels of 8 and 10 minutes were selected. Measurements of physical and mechanical properties of produced boards, including density , water absorption and thickness swelling after 24 hours of soaking, modulus of rupture, internal bond and tensile strength parallel to the surface of boards were made according to ASTM D1037, and then the results were analyzed statistically. The results in this research have indicated that the best treatment for increasing dimensional stability is using kraft lignin content of 10%, press temperature of 200 degrees centigrade and a press time of 10 minutes. 'As concerns mechanical properties, the use of Kraft lignin content of 10% without increasing temperature and press time resulted in desired bending properties, whereas use of Kraft lignin content of5% along with increasing temperature and press time resulted in improvements in internal bond and tensile strength parallel to surface of boards.