Three layer particleboards were manufactured using hygrothermally treated and untreated Laureliopsis philippiana (tepa) particles with urea-formaldehyde (UF) resin. Hygrothermal treatment consisted of autoclaving particles at 150 °C for 90 min (430 kPa) in a steam saturated atmosphere. Density, moisture content, swelling and water absorption were determined. Equilibrium moisture, dimensional variation in length and thickness, as well as length and thickness coefficients per every 1 % change in board equilibrium moisture were also determined after acclimatization at different relative air humidity conditions (20 °C; 40, 50, 60, 70, 80 and 90 % RAH). There were significant differences between particleboards made from control and treated particles. Boards manufactured with treated particles showed a reduction in moisture content, swelling and water absorption. Dimensional stability analysis in response to relative air humidity (RAH) showed that the hygrothermal treatment causes a reduction in equilibrium moisture, a decrease in length and thickness dimensional variation, likewise a reduction in length and thickness swelling coefficients.
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