Response surface methodology study of VOCs in plywood press emissions

Press emissions as a function of plywood panel processing parameters were e valuated by means of a laboratory caul plate press stack collection system. The panel pressing conditions were set at 140 degrees, 150 degrees, and 16 0 degreesC 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 ps f (161.46, 193.75, and 226.04 g/m(2), respectively). The response surface m ethodology (RSM) with the Box and Behnken (2) design was used to define the minimum number of experimental points needed to fully represent a quadrati c regression model. A total of 15 experimental points and 3 extra center po ints were determined, leading to an incomplete 3(3) factorial, design. Resu lts indicated that plywood press emissions are affected by processing param eters in different ways depending on the type of volatile organic compound (VOC) of interest. The quadratic RSM models in terms of the coded factors s howed that press formaldehyde emissions were more sensitive to pressing tim e while methanol and total VOC (TVOC) emissions were more sensitive to resi n content. However, an increase in processing conditions resulted in an ove rall 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 resi n content. The use of an optimization procedure based on the geometric mean of each response desirability function allowed multiple solutions with min imum 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.