Lignin-Phenol co-Polymers as Adhesives
In the last five years a number of researchers have looked at the potential applications of cellulosic ethanol plant lignin residues in preparation of lignin-phenol co-polymers as wood adhesives [70-74]. Zhang and coworkers have recently reported the preparation of lignocellulosic ethanol residue-based lignin-phenol-formaldehyde resin adhesive and its application in bonding plywood. In their experiments, cellulosic ethanol plant residue obtained after the enzymatic saccharification process was used directly as crude lignin for the preparation of lignin phenol co-polymer adhesives. A comparison of the composition of cellulosic ethanol plant residue with the composition of Kraft lignin is shown in Table 10.6.
|
Table 10.6 A comparison of composition of cellulosic ethanol plant residue with the composition of Kraft lignin [71].
NA: not analyzed |
In Zhang and coworkers experiments, cellulosic ethanol plant residue lignin was used to partially replace phenol in the 10-70% range to prepare lignin-phenol-formaldehyde (LPF) adhesive. The result revealed that cellulosic ethanol plant residue lignin with rich hydroxyl group, and less methoxyl groups as well, at lower molecular weight is suitable for synthesis of lignin-phenol-formaldehyde (LPF) adhesive. Furthermore, they reported excellent bonding characteristics of this adhesive in the manufacture of plywood boards. Adhesive properties of ethanol plant residue lignin (ER) replaced phenol-formaldehyde resins are shown in Table 10.7. Performance of plywood boards prepared by using ethanol plant residue lignin (ER) replaced phenol-formaldehyde resins as adhesives are also included in Table 10.7.