How Species and Board Densities Affect Properties of Exotic Hardwood Particleboards

Four exotic hardwood species, kiri (Paulownia tomentosa), virola (Virola spp.), limba (Terminalia superba) and afrormosia (Pericopsis elata), were used to make three-layer particleboards with one species and in combinations of equal parts of two, three, and four species. Mechanical properties were determined by static bending and IB tests. Dimensional stability properties were measured after exposure to 30 to 90 percent and 50 to 90 percent RH and by a 24-hour water-soak test. MOR and MOE increased linearly with increase in wood density and particleboard density. IB increased as board and species density increased, but also was affected to some extent by inherent characteristics of each species. MOR and MOE of mixed species were equal to the weighted mean of the properties of boards made of single species at the same board density. No linear relation was found between dimensional stability and board density, but water absorption was inversely proportional to board density. Thickness swelling was inversely proportional to board density and directly proportional to solid wood volumetric change and in multiple regression was directly proportional to water absorption and solid wood volumetric change. Within the species, an increase in board density generally resulted in a decrease in thickness swelling and an increase in linear expansion.

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