engleski

Dimensional stability of particleboards

When exposed to water or moist environment particleboards tend to swell and expand in all directions. The most visible is swelling in thickness that is higher than horizontal expansion. Thickness swelling of particleboards is influenced by many factors. Among the most important are raw material used, type and share of adhesive used and density of the produced boards. The purpose of this paper is to present the impact of wood species used, share of adhesive and board density on thickness swelling after 24-hour immersion in water. Several three-layer and single-layer particleboards bonded with urea-formaldehyde adhesive were made in laboratory conditions where wood species (three-layer made from spruce, beech, oak and poplar particles), resin content (three-layer, core layer: 6 to 9% ; surface layer: 10 to 13%) and density of board (single-layer with density between 0.7 and 1.0 g/cm3) were altered. In boards where resin content and density was altered industry made particles were used. Thickness swelling was determined with 24-hour immersion test. It was determined that the highest swelling was determined when beech particles were used, and the lowest when oak and spruce particles were used. The biggest changes in swelling and pressure were observed when the resin content was changed in the core layer. The swelling was also influenced by the density of boards. It was determined that the highest swelling was observed in boards with the highest density.

particleboard; thickness swelling; wood species; resin content; density

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