Water vapor sorption isotherm modeling of commercial oriented strand panel based on species groups and resin type

The moisture sorption response of commercial OSB panels at room temperature were examined as a function of humidity. The OSB panels were pine OSB—southern pine (Pinus spp.) mixed with 10–20% of hardwood, usually maple (Acer spp.); aspen OSB—nearly 100% aspen (Populas tremuloides Michx.); and, poplar OSB—40% yellow-poplar (Liriodendron tulipifera L.), 20% maple (Acer spp.), 10% pine and 30% unknown mixture. Two panels from each species group of OSB were chosen based on resin of phenol formaldehyde (PF) face and methyl di-isocyanate core or PF face and PF core. The multi-step sorption isotherm was modeled with the GAB isotherm model and the A/D ratio was determined from the data. Using the model, it was found that the heats of sorption were 6–8 times increased in OSB compared to solid wood. Also, based on the model analysis, the unimolecular layer was smaller compared to solid wood. The average A/D ratio, which is related to the hysteresis, was smaller compared to solid wood.