Dimensionally stable and UV-resistant wood composites fabricated based on waterborne epoxy resin using aminated lignin as curing agent

As an important thermosetting resin, epoxy resin can be impregnated into wood porous structures and cured upon heating to produce high-performance or functional wood composites. To obviate potential environmental hazards associated with volatile organic compound (VOC) emissions during processing, a waterborne epoxy resin (WEP) system containing lignin-based curing agent was designed in this work. The aminated lignin (AL) obtained via the Mannich reaction was well dispersed in the WEP matrix, forming stable waterborne epoxy emulsions. Following the curing reaction between WEP and AL, the resulting films exhibited good chemical stability, indicative of the formation of AL-WEP crosslinked network structures. Dimensionally stable and UV-resistant wood composites were achieved via the impregnation and in-situ curing reaction of AL-WEP emulsion. The anti-swelling efficiency of the wood composites reached 37.9%, and the flexural strength and modulus increased by 59.6% and 49%, respectively, relative to the unmodified wood sample. Furthermore, the wood composites demonstrated favorable UV blocking and resistance performance, attributable to the incorporation of lignin chains containing aromatic skeletons and phenolic hydroxyl groups into the epoxy network and wood structures. This work effectively integrated the respective merits of lignin and WEP into wood, thereby providing a new strategy for the preparation of wood composites with the ability to resist deformation and UV radiation.