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- Particleboard Production from Paulownia tomentosa (Thunb.) Steud. Grown in PortugalPublication . Esteves, Bruno; Aires, Pedro; Sen, Umut; Gomes, Maria da Glória; Guiné, Raquel P. F.; Domingos, Idalina; Ferreira, José; Viana, Helder Filipe dos Santos; Lopes, Luísa P. CruzPaulownia wood has raised high attention due to its rapid growth and fire resistance. The number of plantations in Portugal has been growing, and new exploitation methods are needed. This study intends to determine the properties of particleboards made with very young Paulownia trees from Portuguese plantations. Single layer particleboards were produced with 3-year-old Paulownia trees using different processing parameters and different board composition in order to determine the best properties for use in dry environments. The standard particleboard was produced at 180 °C and a 36.3 kg/cm2 pressure for 6 min using 40 g of raw material with 10% urea-formaldehyde resin. Higher particle size lead to lower-density particleboards, while higher resin contents lead to higher density of the boards. Density has a major effect on board properties with higher densities improving mechanical properties such as bending strength, modulus of elasticity (MOE) and internal bond, lower water absorption but higher thickness swelling and thermal conductivity. Particleboards meeting the requirements for dry environment according to NP EN 312 standard, could be produced with young Paulownia wood with acceptable mechanical and thermal conductivity properties with density around 0.65 g/cm3 and a thermal conductivity of 0.115 W/mK.
- The Influence of Age on the Wood Properties of Paulownia tomentosa (Thunb.) Steud.Publication . Esteves, Bruno; Cruz-Lopes, Luísa; Viana, Helder Filipe dos Santos; Ferreira, José; Domingos, Idalina; Nunes, Leonel J. R.Forests in Portugal are highly dependent on a short number of wood species, and new species with higher profitability are needed. The Paulownia species has generated great interest due to its fast-growing and relatively good wood properties. However, environmental factors have shown that Paulownia grows differently in each case. This study intends to determine the properties of young Paulownia trees from Portuguese plantations to determine the best age to cut the trees according to their use. The chemical composition (extractives in dichloromethane, ethanol and water, lignin, α-cellulose, and hemicelluloses), heating value, elemental analysis (CHNO), inorganic elements and thermogravimetric analyses (TGA), and the most important mechanical and physical properties (density, MOE, bending strength, water absorption equilibrium, moisture content, and dimensional changes) were determined for 1-, 3-, and 5-year-old trees. The results show that, chemically, the extractives increased while hemicelluloses decreased with age, and no trend was found for lignin and α-cellulose. The physical and mechanical properties increased with age, except for the MOE and bending strength. The 5-year-old samples presented the best features for pellet production, namely, calorific power, elemental composition CHNO and sulfur, and inorganic elements.