A study of selected features of Shan Tong variety of plantation paulownia and its wood properties

A study of selected features of Shan Tong variety of plantation paulownia and its wood properties. The study was conducted on three-year-old and representative paulownia tree of the Shan Tong variety, from a plantation in the Kujawsko-Pomorskie Voivodeship, Poland. The three-year-old paulownia tree was 4.2 m high and its diameter at butt level was of 11 cm. The tree provided material for the study from its three-year-old shoot, which was divided into three parts: leaves, branches and the main trunk. According to calculations, this typical paulownia tree (a three-year-old shoot) from a plantation accumulated 4.664 kg of carbon in the part above the ground level, which corresponds to the absorption of 17.101 kg of CO2 from the atmosphere. Taking into account the underground part of this plant, it can be estimated that it absorbed over 30 kg of CO2 (on average, ca. 10 kg CO2 per year). The density of paulownia wood in absolute dry state was ca. 250 kg/m3. The width of annual growth rings was ca. 1.5 cm. This kind of wood is highly porous, with porosity of about 85% (good thermal insulation), and at the same time it has favourable resistance properties characterized by the modulus of elasticity of 4.05 GPa.

Formosolv Pretreatment to Fractionate Paulownia Wood Following a Biorefinery Approach: Isolation and Characterization of the Lignin Fraction

Paulownia is a rapid-growth tree with a high biomass production rate per year and low demand of water, which make it very suitable for intercropping systems, as it protects the crops from adverse climatic conditions, benefiting the harvest yields. Moreover, these characteristics make Paulownia a suitable raw material able to be fractionated in an integrated biorefinery scheme to obtain multiple products using a cascade conversion approach. Different delignification pretreatments of biomass have been purposed as a first stage of a lignocellulosic biorefinery. In this study, the formosolv delignification of Paulownia wood was investigated using a second order face-centered factorial design to assess the effects of the independent variables (concentrations of formic and hydrochloric acids and reaction time) on the fractionation of Paulownia wood. The maximum delignification achieved in this study (78.5%) was obtained under following conditions: 60 min, and 95% and 0.05% formic and hydrochloric acid, respectively. In addition, the remained solid phases were analyzed to determine their cellulose content and cooking liquors were also chemically analyzed and characterized. Finally, the recovered lignin by precipitation from formosolv liquor and the pristine lignin (milled wood lignin) in Paulownia wood were characterized and compared by the following techniques FTIR, NMR, high-performance size-exclusion chromatography (HPSEC) and TGA. This complete characterization allowed verifying the capacity of the formosolv process to act on the lignin, causing changes in its structure, which included both phenomena of depolymerization and condensation.

Suitability of paulownia wood from Malaysia for furniture application

Imported wood resources, especially yellow poplar and Chinese poplar, are increasingly evident in the Malaysian furniture sector due to declining supply of domestic wood materials. In order to reverse this trend, paulownia, a fast-growing forest plantation tree species, is emerging as an alternative wood material source. This study evaluated the mechanical strength, including fatigue life, machining, adhesive bond, screw withdrawal, and finishing properties of paulownia against the imported wood of yellow poplar and Chinese poplar. The results revealed that paulownia has better properties than Chinese poplar, but it is inferior to yellow poplar due to its lower density. In terms of fatigue strength, all the wood species performed comparably equal, with the allowable design stress set at 40% of the wood species’ respective ultimate bending strength. Against these findings, paulownia is a promising alternative wood resource for furniture manufacturing in Malaysia, and it could possibly replace the imported yellow poplar and Chinese poplar. Nevertheless, the successful application of paulownia for furniture manufacturing will depend on its supply volume and economics in the future.

Durability of wood treated with propolis

Propolis is an important antifungal agent found naturally in beehives and used as a food supplement for many purposes. This study aimed to use methanolic propolis extract (MPE) as a treatment material as an antifungal agent for wood preservation. Scots pine and paulownia woods were exposed to Trametes versicolor and Neolentinus lepideus fungi for 12 weeks, and untreated woods were used as the controls. Compared with the control, paulownia wood exposed to N. lepideus had a 47.2% mean mass loss, while the treated wood with 7% MPE had an 11.6% mean mass loss. In addition, a 27.2% mass loss occurred with the control for Scots pine when exposed to N. lepideus, and a 2.5% mass loss occurred with the 7% propolis-treated specimens. Total phenolic content and the phenolic profile of the raw propolis samples were also analyzed. Scanning electron microscopy images showed that the propolis extracts still remained in the wood cells without being degraded after the fungal destruction and the propolis-treated specimens were more durable against fungal decay compared to the untreated control specimens. The results from this study indicated that propolis could be used as an environmentally compatible and natural wood preservative to protect wood against fungal attack.

The effect of heat treatment on thermal conductivity of paulownia wood

The thermal conductivity properties of wood of Paulownia Clones in Vitro 112 were investigated after heat treatment at temperatures of 180 °C, 200 °C and 220 °C. After the treatment, the density decreased by 5.6, 8.9, and 14.1% for the samples heat-treated at 180 °C, 200 °C and 220 °C, respectively. The decrease in the thermal conductivity was 0, 2.6 and 15.7%, respectively. The thermal conductivity of kiri wood after thermal treatment at 220 °C was 0.064 W/mK, which is almost the same as that of thermal insulation materials.