One of the more common materials that go into adhesives that are getting quite a bit of scrutiny lately is formaldehyde. Formaldehyde is "probably" a human carcinogen according to some agencies and a "known" carcinogen by others. It appears that new and more restrictive formaldehyde regulations are appearing especially in the construction and wood working sectors. These regulations could prescribe the use of products with reduced formaldehyde levels that are even more restrictive than the regulations in effect today.

Formaldehyde is widely used in adhesives and it is used as a preservative in paints and finishes. Thus, it can be found in many manufactured goods such as wood composite building materials, insulation fibers, wood furniture, cabinets, and other products that are commonly found in the home. One should also note that formaldehyde naturally occurs in some wood fiber and that is why there are often claims of "no-added formaldehyde" as no wood product is truly "formaldehyde-free".

In the US, a new law came into effect in July of 2010 that limits the formaldehyde levels in wood. The law will be phased-out overtime, but there is a clear trend to limit and eventually eliminate formaldehyde in building products. This new federal Formaldehyde Standards for Composite Wood Act effectively sets national standards at 0.09 parts per million by 2013.

Sometimes these regulations are at odds with true environmental benefits. For example, urea formaldehyde resins may appear to be at odds with any "green" initiative due to formaldehyde emissions. But if one takes into consideration all possible costs and performance requirements, it may be the better choice over greener alternatives in certain applications.

An example of one growing area of green chemistry research in the late 1990s is soy-based adhesives, particularly for wood bonding applications. Researchers found that adhesive made from soy hydrolyzate created a waterproof bond that exceeded industry standards for strength. The United Soybeans Board began development of adhesives to replace both urea formaldehyde and phenol formaldehyde in wood products. Such adhesives also have reduced VOC content.

The development of lignin and tannin adhesives to reduce formaldehyde levels may also lead to less formaldehyde emissions. Methylolated nitroparaffins and hexamine hardeners, belonging to the first class of adhesives above, represent the least expensive and simplest route to adhesive formulation. In panel products, this adhesive also eliminates the formaldehyde emissions to bonded panels strictly to that coming from the wood composite itself. ² The hardeners can also be mixed with any proportion of formaldehyde based hardeners for tannin adhesives.

The performance of adhesives based on tannin extract is similar to exterior or marine grade types. Typical laboratory particleboard and full industrial scale plant trials yielded panel strength results as indicated in Table 1. Generally, steam injection presses are better suited to give high performance results for the exterior grade boards. Accelerators, such as zinc salt, have also been found to provide faster press times.