This report examines various aspects of the formaldehyde emission issue facing the wood composite panel industry in order to help Forintek member companies best navigate this extremely important but increasingly complex problem. It is a state-of-the-art review of fundamentals associated with the formaldehyde emission problem, various standards and regulations, and known technologies for the reduction of formaldehyde emissions. It has distilled and concentrated a vast amount of information based on the literature review, international conferences, known industrial practices and experiences of the authors.
Due to its hydrolytic instability, urea-formaldehyde (UF) adhesive is the main source of formaldehyde emissions from UF-bonded particleboard, medium density fiberboard (MDF), high density fiberboard (HDF) and hardwood plywood through out their service life. There are various technologies available to reduce formaldehyde emission. These are:
1. Chemical modifications of UF resin (lower formaldehyde/urea (F/U) molar ratios, improved resin synthesis procedures, condensed with small amounts of melamine, use of formaldehyde scavengers, use of catalysts/hardeners, cross-linked with methylene diphenyl diisocyanate (MDI) or various combinations of these);
2. Panel post-treatments (anhydrous ammonia treatment, panel overlay, coating, etc.);
3. Manipulation of production process conditions;
4. Using alternative adhesives to replace UF resin;
5. Making binderless panel products.
Some of these technologies can meet the challenges of the most stringent regulations, but likely at higher cost or lower productivity. The most promising options are using commercially available alternative wood adhesives (phenol-formaldehyde (PF), MDI, melamine-formaldehyde (MF), polyvinyl acetate (PVA) or soy) to replace UF. Depending on end use and target market, using ultra-low formaldehyde emitting UF or urea-melamine-formaldehyde/melamine-urea-formaldehyde (UMF/MUF) in combination with an effective catalyst/hardener and/or formaldehyde scavenger can also be a practical option.