Formaldehyde hardwood plywood constructions

The single largest end use for hardwood plywood is interior wall panels, generally 3-ply and 1/4 and thinner, and frequently machined with decorative v-grooves. Furniture, cabinets, door skins and a number of specialties complete an array of end use products. Many of the non wall panel products can be characterized as being industrial panels and are of 5 or more ply veneer core, 3-ply particleboard core, or 3-ply medium density fiberboard (MDF) core construction. Broad end use patterns indicate that interior wall panels represent approximately 55% of total hardwood plywood consumption. Furniture, cabinets, and fixtures represent about 30%, and door skins and specialty products about 15% (2), Potential sources of formaldehyde in two of the more typical hardwood plywood constructions are displayed in Figure 1. 

Figure 1. Potential sources of formaldehyde in two typical hardwood plywood constructions.

Reduction in the emission characteristics of unfinished hardwood plywood is currently being achieved primarily by the use of low formaldehyde to urea molar ratio formulations. For the manufacture of hardwood plywood and particleboard, formaldehyde to urea molar ratios have been reduced to a range of 1.15/1 to 1.3/1. An important caveat low F/U ratios perhaps should be considered a proxy for the potential to reduce emissions through improved urea-formaldehyde adhesive technology rather than the exclusive means for improvement. Reducing the F/U ratio is not always the most effective way of reducing emissions in consideration of the variety of hardwood plywood constructions, products, and thicknesses. ... 

Some report that over 50 percent of the urea-formaldehyde resins consumed went into particleboard. This is brought out because there may be a shift away from urea resin for certain types of oriented particleboard used in structural plywood constructions. Historically, particleboard has been used for inner plies as previously mentioned in some hardwood plywood. There is now one plant in production in Idaho which produces mechanically oriented strand particleboard for use specifically as core for softwood plywood production. It is anticipated that this trend to some degree will increase in the future, and phenolic resins appear to be the mechanism with which this particleboard will be bonded. 

The types of adhesives suitable for laminating beams are restricted by the conditions of application and by their end-use requirements. A wider choice of adhesives for plywood depends on whether softwoods or hardwoods are used, whether they are required for internal or external exposures, or whether they are to be used for ornamental or structural purposes. Thus phenol-formaldehyde types would be used for marine or exterior construction uses urea-formaldehyde types would be advantageous for cold pressing, or melamine-urea adhesives might be preferred for hardwood plywood, or lumber-core panels used in furniture production. 

Formaldehyde emission and/or formaldehyde space level potential can be related to both construction type and product end use. While the American National Standard for Hardwood and Decorative Plywood (1 ) references eight different types of construction, three are most important in the context of formaldehyde ... 

Columbia Forest Products applied the principle that imparts adhesive ability to the blue mussel, to design a soy-based formaldehyde-free technology in the construction of hardwood and plywood products. The WhalePower Company designed wind turbine blades using the Tubercle Technology to help them be quieter, more reliable when winds fail, and perform better in turbulent winds (WhalePower 2013). The technology is based on the idea that humpback whales are agile in spite of their size because of bumps on their fins. 

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