Adhesives for Wood

Many of the factors discussed in connection with the durability of aluminum joints are applicable to wood bonds. However, there are a number of differences. Wood is porous and able to absorb a large quantity of water. This can produce dimensional changes, which in turn cause changes of the stress distribution in the joint. Wood substrates are usually preconditioned to a known moisture content before bonding. Many applications involve exposure to changing environmental conditions, so that cyclic variations of stress in the joint need to be considered when designing for long-term durability. 

The results of natural and accelerated aging have shown that moisture and heat are the most important factors in determining loss of joint strength. 

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Both the wood-based panel industry and the adhesive industry show a high commitment to and great capability towards innovation. The best evidence for this is the considerable diversity of types of adhesives used for the production of wood-based panels. Well-known basic chemicals have been used for a long time for the production of the adhesives and their resins, the most important ones being formaldehyde, urea, melamine, phenol, resorcinol and isocyanate. The greater portion of the currently used adhesive resins and adhesives for wood-based panels is produced with these few raw materials. The how to cook the resins and the how to formulate the adhesive become more and more complicated and sophisticated and are key factors to meet today s requirements of the wood-based panel industry. 

Adhesives based on isocyanate (especially PMDl, polymethylene diisocyanate, more exactly polymeric 4,4 -diphenylmethane diisocyanate) have been used for more than 25 years in the wood-based panel industry [88], but still have a low market value in the wood-working industry compared to systems based on UF-, MUF- or PF-resins. The main application is the production of waterproof panels, but also the production of panels from raw materials that are difficult to glue, like straw, bagasse, rice shells or sugar cane bagasse. They can be used as adhesives for wood-based products like particleboard, oriented strandboard (OSB), laminated strand lumber (LSL), medium-density fiberboard (MDF) or... 

Specification for synthetic resin adhesives for wood. Part 2 Close contact joints. British Standard BS 1204-1965, 1965. 

Urea- and melamine-formaldehyde resins are used as moldings, lacquers, and adhesives (for wood), also as textile additives (increased crease resistance) and paper additives (improved wet strength). 

The objective of this work was to demonstrate the utility of organosolv red oak lignin (a projected cheaper polyphenol than phenol) in phenolic adhesives for wood composites. This work involved three stages ... 

All these syntheses produce interesting products in terms of thermal stability. It must be noted that this muconic acid has been used by the same authors [198] to participate to the hardening of epoxy resins where it is soluble above 120 °C. These resins are mainly used as adhesives for wood. 

The largest and oldest chemical intermediate use for methanol is formaldehyde. Over half of the methanol currently consumed in the world goes into formaldehyde production. Formaldehyde is produced by the catalytic oxidation or the oxidative dehydrogenation of methanol The major outlet for formaldehyde is amino and phenolic resins. These resins are in turn used in the manufacture of adhesives for wood products, molding compounds, binders for thermal insulation and foundry resins. Formaldehyde is also consumed in the production of acetal resins, pentaerythritol, neopentyl glycol, trimethylolpropane, methylenediphenyldiisocyanate (MDI), and textile treating resins. 

D 3930 Specification for Adhesives for Wood Based Materials for Construction of... 

The fourth research category mentioned in the NFPA review relates to enhancing the performance of established natural adhesives for wood bonding to provide durability equivalent to that of the synthetics. This is especially desirable where natural adhesives presently offer significant performance advantages over synthetics in terms of fast hot-press times, short-cycle cold cure, or improved gap-filling properties. Specific examples would include ... 

In this respect, the most important future application of lignin will be as a natural plastic in the field of general polymer applications, especially as adhesives for wood composites. 

Of course, an enzyme applied to a technical process in such a dimension as adhesives for wood materials has to have certain properties. It must be ... 

Kreibich, R. E., Use of Bark Tannins in End-Joint Adhesives for Wood. Final Report-Phase I to the USDA Small Business Innovation Research Program on grant 86-SBIR-8-0126, R. E. Kreibich, Auburn WA., 1987. 

Johns, W. E. Jahan-Latibari, A. In Adhesives for Wood Research, Applications, and Needs Gillespie, R. H., Ed. Noyes Publications Park Ridge, NJ, 1984. 

Phenol-formaldehyde type polymers had been the only exterior-durable adhesives for wood bonding, until the recent limited use of isocyanates. Both systems are petrochemical-based. Several researchers substituted carbohydrates for part of phenolic adhesives (1-4) > producing solid, fusible novolak resins. Recently, reaction of carbohydrate acid-degradation products with phenol and formaldehyde has produced liquid resols (5). Gibbons and Wondolowski (6,7) replaced a considerable amount of phenol with carbohydrate and urea to pro-... 

JIS K 6806 1985 Water-based polymer-isocyanate adhesives for wood. JIS K 6860 1974 General recommended practices for atmospheric exposure of adhesive bonds. 

Starch xanthates have been suggested for use as adhesives for wood veneers, and as textile sizes. "... 

Use Resorcinol-formaldehyde resins, dyes, pharmaceuticals, cross-linking agent for neoprene, rubber tackifier, adhesives for wood veneers and rubber-to-textile composites, manufacture of styphnic acid, cosmetics. 

A major use of phenol is in phenol-formaldehyde adhesives for wood. Tannins are polyphenols from plants, as in bark,46 that may be able to replace phenol in such adhesives. A typical repeating unit is shown in (12.18). 

When chloroprene was grafted onto cationic aminated starch, a latex was obtained that imparted wet strength to paper and also served as a pressureless adhesive for wood 2951 Starch dialdehyde when grafted with acrylonitrile, methyl methacrylate, or both, produced a biodegradable filler for poly (vinyl chloride) plastics.2942 Starch xanthates grafted with vinyl monomers were also used to produce additives for reinforced foamed rubber.2944,2945... 

Lambuth, A.L. Protein adhesives for wood. Advanced Wood Adhesive Technology A. Pizzi, K.L. Mittal, Eds. Marcel Dekker Inc. New York, 1994 pp. 259-281. 

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