Objective The traditional adhesive application process for wood scrimber is labor-intensive, energy-consuming in drying, and difficult to scale up for continuous production. To address these issues, this paper innovatively employs a roller-pressing resin impregnation method to directly apply resin to units with high moisture content. The paper systematically investigates the impact of this method on the physical and mechanical properties of wood scrimber, providing theoretical support for optimizing the production process.
Method Using roller-pressing resin impregnation technology, phenol-formaldehyde (PF) resin was directly applied to poplar units with 30% moisture content. The PF resin application process was optimized by adjusting the compression ratio and the number of roller-pressing. The distribution of resin and microstructure was characterized using micro-computed tomography, scanning electron microscopy, and transmission electron microscopy. The chemical interactions between resin and wood were analyzed using Fourier-transform infrared spectroscopy and X-ray diffraction. Additionally, the water resistance of wood scrimber was evaluated using a boiling-drying-boiling cycle test, and its mechanical properties were assessed using a three-point bending test.
Result Increasing roller pressure and the number of presses significantly enhanced resin application in high-moisture-content units. Compared with wood scrimber produced by traditional cage-type impregnation method, the wood scrimber produced by roller-pressing impregnation method exhibited 41.12% and 21.04% reductions in thickness swelling rate and width swelling rate, respectively, along with a 10.57% increase in modulus of elasticity (MOE). The roller pressure caused further damage to the cells within the units, and the expansion of pre-existing cracks, allowing resin to penetrate into the cell cavities and cell walls under negative pressure, forming cross-links with cellulose. Chemical analysis further confirmed that PF resin filled intercellular spaces and established a three-dimensional network structure, which inhibited hygroscopic swelling and enhanced its density and crystallinity. Consequently, this technology achieved more uniform resin distribution within units, substantially improving the water resistance of wood scrimber, and inhibited cell wall spring-back upon water absorption, reduced surface bulging (jump fibers), and enhanced overall board homogeneity. Moreover, the phenolic resin that penetrated the cell walls enhanced the MOE of reconstituted wood.
Conclusion The roller-pressing resin impregnation technology for high-moisture-content units significantly enhances the water resistance and modulus of elasticity (MOE) of wood scrimber by optimizing resin distribution and interfacial bonding. Simultaneously, this technology also reduces energy consumption by eliminating conventional drying process before gluing process. This technological breakthrough enables continuous fiber separation-impregnation-drying production workflows, providing novel approaches for optimizing manufacturing processes and promoting the sustainable development in wood scrimber.
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