Response surface methodology study of VOCs in plywood press emissions.

Press emissions as a function of plywood panel processing parameters were evaluated by means of a laboratory caul plate press stack collection system. The panel pressing conditions were set at 140°, 150°, and 160°C for the pressing temperature. The pressing time was set at 7,9, and 11 minutes. Resin solids content was set at 0.033, 0.040, and 0.046 psf (161.46, 193.75, and 226.04 g/m 2 , respectively). The response surface methodology (RSM) with the Box and Behnken (2) 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 center points were determined, leading to an incomplete 3 3 factorial design. Results indicated that plywood press emissions are affected by processing parameters in different ways depending on the type of volatile organic compound (VOC) of interest. The quadratic RSM models in terms ofthe coded factors showed that press formaldehyde emissions were more sensitive to pressing time while methanol and total VOC (TVOC) emissions were more sensitive to resin content. However, an increase in processing conditions resulted in an overall increase of press emissions. On the other hand, formaldehyde and TVOC post-pressing emissions were more sensitive to resin solids content than to pressing temperature and time, and decreased with the increase of the resin content. 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 situation being 1.0.