Comparing lignin derived from black liquors of alkaline sulfite-AQ, soda-AQ and kraft processes as a filler-extender in the poplar plywood

According to the importance of urea formaldehyde resin in plywood industry and to replace a suitable filler for this resin with wheat flour (common filler), lignin drived from three black liquors including alkaline sulfite-AQ, soda-AQ and Kraft evaluated as filler-extender for urea formaldehyde resin in the plywood manufacture. For this reason any of the four types of lignins were used at 0, 10, 20 and 30% dry weight of resin.After that, the physical and mechanical properties of samples including thickness swelling after 2 and 24 hours immersion in water, flexural strength and modulus of elasticity parallel and perpendicular to fiber the surface layer and shear strength were measured.The results of this study showed that increasing thelignin of alkali sulfite-anthraquinone and then kraft lignin, flexural strength and modulus of elasticity parallel to the fiber surface layer increased.Also, the bonding shear strength of the samples using three types of lignins increased. On the other hand, the use of these three types of lignin, improved the dimensional stability of the boards.The results show the superiority of lignin from alkaline sulfite anthraquinone process compared to other lignins to improving the mechanical properties of plywood.