Adhesive related VOC- and formaldehyde-emissions from wood products
Tests, regulations, standards, future developments
The requirements on the environmental and health compatibility of materials for interiors increase more and more within the last few years. Formaldehyde, volatile organic compounds (VOC), easy volatile and heavy volatile compounds (VOC and SVOC) respectively are part of the most significant pollutions of the indoor air of buildings. Certain VOC cause smell nuisances. Wood-based panels are important materials for the manufacture of buildings, furniture and other products. All wood products emit small amounts of formaldehyde. The formaldehyde release caused by formaldehyde-based adhesives, paints and coatings is of much more significance. The quantity of formaldehyde released from wood-based panels depends on a number of exogenous (e.g. atmospheric moisture, temperature, number of air exchanges) and endogenous factors (e.g. wood species, waste material, type of resin, conditions of manufacture, post-treatment of the board). The formaldehyde emissions of wood-based panels vary between very small values just above the values of untreated wood particles, if bonded with diisocyanate adhesives or phenolformaldehyde resins, and values in the range of emission class E1 and above, if bonded with urea-formaldehyde resins. The formaldehyde emissions by UF-resins can be reduced e.g. by formaldehyde-binding agents (scavengers) such as urea, ammonium compounds, melamine or resorcinol. Challenges for the wood-based industries are the reclassification of formaldehyde by the World Health Organisation advisory board IARC as carcinogenic to humans and the trials of different European state, to regulate the emissions of building products. There has been much progress in reduction of formaldehyde emissions of wood-based panels and other wood products during recent years. The release of volatile organic compounds (VOC) concerns especially wood-based panels and other wood products. The VOC emission of wood-based panels is infuenced in particular by the wood (e.g. monoterpenes from softwood), by the type of resin (e.g. acetic acid release in alkaline medium), board manufacture (pressing conditions), post-treatment of board and utilization conditions. Different national and international commitees entered into the question of the evaluation of VOC emissions of building products. In Germany the Committee for Health-related Evaluation of Building Products (Ausschuss für die gesundheitliche Bewertung von Bauprodukten - AgBB) has elaborated test criteria and as a result develops an assessment scheme for VOC and SVOC emissions from floor coverings and from adhesives for same. The scheme sets healts-related quality standards for the future manufacture of building products for interiors and it shall support the development of particularly low-emission products. As for the homologation of floor coverings, which have to fulfil the requirements on the low-flammability, in view of the building supervision the emission tests for formaldehyde, VOC and SVOC are compulsory now. It hs to e expected that the assessment scheme elaborated by the AgBB will be expanded on other building pruducts in the near future. The release of formaldehyde and VOC from wood flakes and wood-based panels, most important test methods regarding the formaldehye and VOC emissions of wood-based panels, the VOC and formaldehyde regulations in Europe are presented in the paper. The implementation of fair regulations taking into consideration the natural origin and composition of wood is a question needing the full commitment of the forest and wood chain.