Cocuring of Epoxidized Soybean Oil-Based Wood Adhesives and the Enhanced Bonding Performance by Plasma Treatment of Wood Surfaces

Abstract

Application of epoxidized soybean oil (ESO) in the wood industry as an adhesive has been limited due to the difficulty in fast curing ESO. Due to the advantages of the ureaformaldehyde (UF) resin, like low cost, high molecular weight, rich functional groups, as well as fast self-curing property, fast cocuring ESO-UF adhesives were prepared by mixing UF with ESO in different ratios (15−50%). Bonding performance tests indicated that the ESO-UF adhesives well balanced bonding strengths and the formaldehyde emission level; especially, the adhesives provided satisfactory water resistance. Structural characterization of cured ESO-UF adhesives showed that a copolymerization reaction occurred between epoxy groups of ESO and the hydroxyl groups of UF. Combined with gliding arc discharge (GAD) plasma treatment of the veneer surface, better bonding performances were achieved. X-ray photoelectron spectroscopy (XPS) analysis on the wood surfaces showed that the GAD treatment significantly increased the content of oxygencontaining groups like −OH and −COOH through oxidation and degradation of the chemical components on the wood surface. The generated reactive groups on the wood surface participated in the curing reaction of ESO-UF adhesives and led to improved bonding performances. Thus, the ESO-UF-activated wood surface (ESO-UF-AWS) system was developed in this study. The results of this study have demonstrated that the combination of seeking an efficient cocuring agent along with activating the wood surface is a valid strategy for realizing applications of ESO in the wood product industry.

Preparation of Environmentally Friendly Glueless Boxwood Timber by Acidic Environmental Treatment and High-Temperature Pressing

“…The relative content of lignin on the wood surface increases and the content of polysaccharides (cellulose and hemicellulose) decreases after treatment [ 23 ]. The decrease in the O1 peak area and the increase in the O2 peak area of DW compared to the RWP fraction indicate that the percentage of oxygen atoms with high binding energy on the surface of wood fibers increases after acid treatment [ 24 ].…”

Layer-by-layer assembling redox wood electrodes for efficient energy storage

“…New bands (1,743 and 1,625 cm -1 ) observed for CNTs@TrW are attributed to C=C stretching from functionalized CNTs [31] . The band at 1,592 cm -1 in TrW related to C=O stretching of lignin shifts to 1,576 cm -1 in CNTs@TrW, which is attributed to π-π and hydrogen bonding between CNTs and TrW surface [32,33] . The absorbance at 2,890 cm -1 is separated into two different peaks at 2,850 and 2,927 cm -1 due to the chemical interaction between CNTs and TrW in CNTs@TrW composites.…”

Recent progress of biomass in conventional wood adhesives: a review

“…52 Protein is usually used to blend with UF resin to improve the bonding strength and water resistance of the adhesive, and reduce the formaldehyde emission of the adhesive during use. Duan et al 18 prepared a fast-curing ESO–UF adhesive by mixing UF resin and epoxidized soybean oil (ESO) in different proportions (15–50%). This ESO–UF adhesive has a good bonding strength and formaldehyde release balance; in particular, the adhesive provides satisfactory water resistance.…”

“…16 The conventional production process for “trialdehyde adhesive” involves the release of formaldehyde gas, precipitating both environmental contamination and health hazards. Substituting biomass for the requisite formaldehyde in the production process, 17 or blending biomass with formaldehyde adhesives, 18 offers an avenue for diminishing formaldehyde emissions during application. Furthermore, natural components like soy protein, lignin, and tannic acid confer distinct advantages as adhesive raw materials, characterized by reduced material costs, diminished carcinogenic volatile emissions, and potential for sustainable development.…”