Part 1 : Plywood press emissions as a function of panel processing parameters were evaluated by means of a laboratory caul plate press stack collection system. Panel pressing temperatures were 140, 150 and 160°C and pressing times 7, 9 and 11 minutes. Glue spreads in terms of resin solids were 0.033, 0.040 and 0.046 lbs/ft² (161.46, 193.75, 226.04 g/m², respectively). Response surface methodology (RSM) with the Box and Behnken design was used to define the minimum number of experimental points needed to fully represent a quadratic regression model. A total of 15 experimental points and 3 extra centre points was determined leading to an incomplete 33 factorial design. Results indicated that plywood press emissions are affected by processing parameters in different ways depending on the type of the volatile organic compound of interest. The quadratic RSM models in terms of the coded factors showed that formaldehyde emissions were more sensitive to pressing time while methanol and total volatile organic chemical (TVOC) emissions were more sensitive to resin content. However, an increase in any processing parameter resulted in an overall increase in press emissions. On the other hand, the amounts of formaldehyde and TVOC emitted from the resulting plywood panels were more sensitive to resin solids content than to pressing temperature or time, showing decreases with increasing resin contents. The use of an optimization procedure based on the geometric mean of each response desirability function allowed multiple solutions with minimum press emission levels with a desirability value of up to 0.97 when the imposed limits during the optimization procedure were less stringent. The ideal desirability value is 1.0.
Part 2 : A laboratory method was developed to evaluate the effects of key wood particleboard processing parameters on hot-press emissions of volatile organic compounds (VOCs). The method was based on an enclosed caul plate system that trapped the gas stream containing the VOCs emitted during board pressing. The hot gases trapped in the caul plate were cleaned through cold traps containing distilled water or organic solvent for non-water-soluble chemicals, in order to condense and trap VOCs from the air stream. Formaldehyde was quantified by the chromotropic acid method (NIOSH* modified method), while methanol and phenol were quantified by gas chromatography/flame ionisation detection (GC/FID. Other VOCs were characterised and quantified by gas chromatography/mass spectroscopy (GC/MS). Formaldehyde emissions as well as methanol, phenol and total volatile organic compound (TVOC) emissions, which consisted mainly of terpenes, increased with platen temperature, pressing time and mat resin solids content conversely, subsequent emissions from the panels themselves decreased. Inversely, panels produced showed decreasing emission levels when processing parameters such as resin content, pressing time and pressing temperature were increased. Furnish composition significantly affected press emissions in terms of both nature and amount of chemicals emitted. The surface moisture content of the mat also seems to increase press emissions but further work needs to be conducted to support this observation. This includes works on the response surface methodology in the study of plywood press emissions of volatile organic compounds; Press volatile organic compound emissions as a function of wood particleboard processing parameters