Ionic liquid modified lignin-phenol-glyoxal resin: a green alternative resin for production of particleboards

The aim of this research was to evaluate the properties of particleboard panels bonded with ionic liquid treated lignin- phenol- glyoxal (LPG) resin. For this purpose, soda bagasse lignin was modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid and then various contents of virgin and modified lignin (20, 30 and 40 wt% based on weight of phenol), phenol and glyoxal were used for synthesis of LPG resins. After resin synthesis, thermal and physicochemical properties of the synthesized resins such as curing behavior, gelation time, viscosity, solid content and density were measured. Finally, the resins so prepared were used for laboratory particleboard manufacturing. The panels physical (water absorption, thickness swelling) as well as mechanical (MOE, MOR and internal bond strength) properties were measured according to standard methods. The resins tests indicated that modification of lignin with ionic liquid not only can accelerate the gelation time and increase viscosity, density and solid content of LPG resins but also decrease the temperature required for curing the LPG resins. Based on the results of this work, the mechanical strength and dimensional stability of the particleboards bonded with a LPG resin can be improved by using modified lignin. The particleboards prepared with the LPG resin, using either modified or virgin lignin, presented higher water absorption as well as weaker mechanical strength than those prepared with the control PF resin. However, there does not appear to be any statistically significant difference between the some properties of the panels bonded with the control PF resin and those bonded with the LPG resin containing modified lignin.