Wood Adhesives Science and Technology
FS-FPL-4703

Wood Adhesives and Adhesion FAQs

Veneer and Panel Problems

1. Why do we get failures (blisters or splits) in veneers (or their finishes)in cabinetry or furniture, especially after a delayed time?

A: Look answers in the diagnostic guide .

2. Why does a certain veneer or laminate not stick to a composite panel product (particleboard, MDF)? One or the other may be treated with chemicals.

A: The problem could be, for example, moisture expansion incompatibilities, insufficiently strong adhesive, complications of the treatment chemical (for example, pH or accumulations of treatment chemical at the surface that defeat bonding)

3. Will this “substance” that appears on the surface of the wall panel or veneer affect its bond to other wood?

A: It is probably best to talk to a scientist, either in the Adhesives unit or perhaps in the Center for Wood Anatomy Research unit. Please feel free to contact us at (608) 231- 9200.

Questions on Adhesives, or Glues

4. We’re having problems with (dark) glue bleedthrough, or with gluelines reacting with wood to color the wood (dark or pink).

A: The bleedthrough problem in wood veneers relates to a number of factors, including darkness of the resin or colored hardener, wood species, veneer thickness, grain orientation, moisture content, pressure, and other factors.
The problem of pink stains shows up on the outer sides of veneer as a consequence of effects from bond lines below. Usually the pink color comes from interactions of components in certain wood species that react to acidic components in certain adhesives [particularly urea-formaldehyde resins and acidic (pH 3-4) PVA - type resins]. Casein and starch glues, because they are alkaline, cause stains on woods high in tannins, including oak, mahogany, chestnut, walnut, beech, cherry, and maple.Casein can affect redwood. If iron fasteners are used on a wood rich in tannins, the wood can become colored dark in those areas. It is probably best to talk to a scientist, either in the Adhesives unit or perhaps in the Center for Wood Anatomy Research unit. Please feel free to contact us at (608) 231- 9200.

5. Is this adhesive toxic or unsafe or a pollutant?

strong>A: Some adhesives have components that should not be inhaled or allowed to stay in contact with the skin/eyes for any significant length of time. Check the container or any materials information sheets that come with an adhesive or are available from the manufacture's web site, call the manufacturer to talk to a representative or ask for a Materials Safety Data Sheet (MSDS). Some adhesives, such as common white or yellow polyvinyl acetate glue, are relatively safe. Some other adhesives will bond to skin and not let go if they cure, which sometimes can be within a matter of minutes.

6. Is there a substitute (maybe “greener”) adhesive that would perform well for the use I have in mind?

A: Browsing our adhesive selection chart is a good first step. If you need more specific advice, consult woodworking books or sales people, or try looking on the web for adhesive manufacturers that carry a range of adhesive products and can advise you on an appropriate choice.

7. What adhesive can I use to bond wood together for a personally built, wooden sport airplane?

A: There are no standards for this application, but phenol-resorcinol-formaldehyde (PRF) adhesive is considered the most conservative choice. However, it results in a dark bond line and requires good clamping to get a good joint. At least one epoxy has been used in some sport aviation planes. We have developed a primer that allows epoxy and polyurethane to have durability much closer to PRF resins, based on accelerated tests, but at this point we do not have long-term, actual use data to confirm its success. For primer information, see the publications search function and searchfor HMR.

Wood Species Effects

8. Why is this wood species hard to bond well (durably)?

A: The problem could be associated with: dense species of wood; problematic wood extractives accumulating at the surface to prevent good bonding; or, large shrinkage or swelling dimensional changes that overstress bonds (for example, some types of adhesives cannot accommodate significant long-term stresses without creeping or even separating from wood).

9. Can I use this wood species (and some adhesive) for a particular application?

A: The answer is often highly specific to the application, and it’s best to talk with one of the scientists.

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