Evaluation of parameters influencing the VOC emissions from plywood
Emissions from building products are a matter of concern due to upcoming regulations with regard to the European building construction directive. Consequently, it is essential to understand the emission potential of wood products and the sources of those emissions. Since the evaporation and formation of volatiles from wood products are related to the temperature the material is exposed to during manufacture, the process parameters may have a major impact on their emission characteristics. In this paper the influence of selected plywood process parameters are evaluated with respect to the emission of formaldehyde and volatile organic compounds (VOC). Plywood was manufactured with varying soaking, drying, and pressing temperatures. Emissions from the manufactured plywood were tested according to EN 717-2 and ISO 16000-9. An increase in the log soaking temperature resulted in an increase in formaldehyde release from panels made of birch, pine sapwood and spruce. Higher drying and pressing temperatures also resulted in increased formaldehyde release from samples made from birch and pine heartwood. Wood species had a major impact on the VOC emissions from plywood. Pine heartwood exhibited the highest level of total VOC emissions, followed by pine sapwood, spruce and then birch. The most relevant substances were found to be terpenes, aldehydes and organic acids. An increase in log soaking temperature led to a reduction in emissions from pine and spruce, but to a minor increase from birch. With higher drying and pressing temperatures, the emissions were lower from pine and birch after 28 days testing.