DETERMINATION OF SORPTION ISOTHERMS OF SCOTS PINE (PINUS SYLVESTRIS L.) WOOD STRANDS LOADED WITH MELAMINE-UREA-PHENOL-FORMALDEHYDE (MUPF) RESIN

The purpose of this study was to determine the sorption isotherms of Scots pine (Pinus sylvestris L.) wood strands, taken from a previously prepared strand-adhesive mass, used for the production of a three-layer oriented strand boards (OSB). The study investigated three loading levels of Melamine-Urea-Phenol-Formaldehyde (MUPF) resin used for gluing the OSB, constituting 5, 10, and 15 % of the wood strands dry weight. The obtained experimental sorption data were approximated using a two-parameter Nelson's sorption model and a three-parameter Guggenheim-Anderson-deBoer (GAB) model. It was shown that gluing the strands with 5, 10, and 15 % MUPF resulted in the reduction of equilibrium moisture content (EMC) by about 2 % for the adsorption phase, and about 1 % for the desorption phase, as well as a significant increase in sorption hysteresis, as compared to resinless strands. No proportional relationship was found between the gluing degree and equilibrium moisture content reduction. This indicates that MUPF resin applied on the wood strand surface had little effect on reducing hygroscopicity and increasing dimensional stability of OSB.