基于预水解的木质素基胶黏剂制备及其胶合机理OA

Traditional aldehyde-based adhesives,particularly the widely used urea-formaldehyde resin,have long served as a cornerstone of the wood-based panel industry.However,these adhesives face major challenges due to formaldehyde emissions during both the curing process and long-term use.The persistent and unavoidable release of free formaldehyde not only severely deteriorates indoor air quality,posing potential health hazards to occupants—such as respiratory issues and allergic reactions—but also starkly contradicts the principles of green,low-carbon,and sustainable development fervently championed by today's wood-based panels sector.As environmental consciousness rises and regulatory standards become stricter,the demand for eco-friendly alternatives has become increasingly urgent.To tackle this critical technical challenge,this study pursued an innovative approach by utilizing Mason pine(Pinus massoniana Lamb.),poplar(Populus tomentosa Carr.),and wheat straw(Triticum aestivum L.)as raw materials.With an eco-friendly pre-hydrolysis process,milled wood lignin(MWL)was extracted from the production residues,providing a sustainable and low-impact source for adhesive components.The chemical structural changes of MWL were examined using a suite of advanced analytical techniques,including potentiometric titration,alkaline nitrobenzene oxidation,molecular gel chromatography,thermogravimetry,differential scanning calorimetry,and nuclear magnetic resonance spectroscopy.Subsequently,three-layer plywood samples were expertly fabricated using hot-pressing with varying MWL.Notably,MWL derived from Mason pine residues displayed higher phenolic hydroxyl content,which boosted its reactivity and bonding capabilities.By optimizing the hot-pressing parameters,the dry bonding strength achieved an impressive 4.34 MPa at 150℃for 4.17 min/mm with a MWL single-side application of 100 g/m2.The cross-linking mechanism was further clarified,revealing that,during hot-pressing,some lignin underwent depolymerization and recondensation.This process resulted in the formation of a uniform adhesive layer on the plywood surface and a strong cross-linked structure within the plywood,ensuring outstanding bonding strength and durability.Remarkably,the dry strength of MWL from Mason pine residues increased by an astonishing 214％after pre-hydrolysis at 160℃for 30 min.This groundbreaking discovery offers fresh insights into the design of high-performance lignin-based adhesives and is expected to accelerate the transformation and upgrading of the wood-based panel industry towards zero-formaldehyde formulations.