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- Water-related properties of Pinus pinaster wood treated by different methodsPublication . Domingos, Idalina; Ferreira, José; Cruz-Lopes, Luísa; Esteves, BrunoA study was made of water-related properties of Pinus pinaster wood impregnated with paraffin or modified by heat treatment or furfurylation. Treated woods were submerged in water for periods ranging from 2 to 1680 hours. Water absorption, swelling, and dimensional stability in the radial and tangential directions – expressed as Anti-Shrinking Efficiency (ASE) – were determined. Water absorption increased with time, reaching approximately 140% after 1680 h for untreated and heat-treated wood, and 60% for paraffinated and furfurylated wood. The rate of swelling differed between the first hours of soaking and after prolonged immersion. The final swelling was approximately 9% and 6% for untreated pine, 8% and 4% for paraffinated pine, 5.5% and 3% for heat-treated pine and 2.5% and 1% for furfurylated pine (in the tangential and radial directions respectively). At the end of the soaking test, furfurylated pine had the best ASE of approximately 80% and 70% in the tangential and radial directions respectively, followed by heat-treated pine with 44% and 34%, and paraffinated wood with 35% and 13%. [
- Densification and heat treatment of maritime pine woodPublication . Esteves, Bruno; Ribeiro, Fábio; Cruz-Lopes, Luísa; Ferreira, José; Domingos, Idalina; Duarte, Marta; Duarte, Sónia; Nunes, LinaPine (Pinus pinaster Ait.) wood samples were subjected to a combined treatment by densification and heat treatment. Samples were densified before and after heat treatment. The heat treatment was made inside an oven at 190ºC during 2 to 6 h and wood densification was made in a hot press at around 48 bar pressure and temperatures between 160ºC and 200ºC for 30 min. Compression-set, compression-set recovery after three cycles of water soaking followed by oven drying, density, hardness, bending strength and stiffness and durability against subterranean termites were determined after the treatment. Results show that densification increases density, hardness, bending strength, stiffness and durability against termites. Heat treatment applied after the densification is more effective in reducing compression-set recovery than if applied before.
- Changes in the content and composition of the extractives in thermally modified tropical hardwoodsPublication . Esteves, Bruno; Ayata, Umit; Cruz-Lopes, Luísa; Brás, Isabel; Ferreira, José; Domingos, IdalinaChemical composition of wood is known to change during thermal treatments. Two species grown in Turkey, afrormosia (Pericopsis elata) and duka (Tapirira guianensis) were heat treated according to Thermowood® method. Lignin, cellulose, hemicelluloses and extractives in dichloromethane, ethanol and water were determined. Wood extracts were analysed by gas chromatography with mass detection and existing compounds were identified by NIST17 database. Results show that hemicelluloses and cellulose content decreased for both heat-treated woods along the treatment while lignin percentage increased. The analysis of extractives has shown several compounds normally associated to lignin thermal degradation that increased along the treatment. At the same time several compounds associated to carbohydrate thermal degradation were found in all the extracts for both heat-treated woods. These founding have allowed the understanding of the degradation pattern of wood during thermal modification. There was not much difference between afrormosia and duka woods structural compounds behaviour along thermal modification. However, the variation of the amount of extractives along the treatment depended on the species.
- Termite resistance, chemical and mechanical characterization of paulownia tomentosa wood before and after heat treatmentPublication . Esteves, Bruno; Ferreira, Helena; Viana, Helder Filipe dos Santos; Ferreira, José; Domingos, Idalina; Cruz-Lopes, Luísa; Jones, D.; Nunes, L.The introduction of new species in forest management must be undertaken with a degree of care, to help prevent the spread of invasive species. However, new species with higher profitability are needed to increase forest products value and the resilience of rural populations. Paulownia tomentosa has an extremely fast growth. The objective and novelty of this work was to study the potential use of young Paulownia trees grown in Portugal by using heat treatment to improve its properties, thereby allowing higher value applications of the wood. The average chemical composition of untreated and heat-treated wood was determined. The extractive content was determined by successive Soxhlet extraction with dichloromethane (DCM), ethanol and water as solvents. The composition of lipophilic extracts was performed by injection in GC-MS with mass detection. Insoluble and soluble lignin, holocellulose and α-cellulose were also determined. Physical (density and water absorption and dimensional stability) and mechanical properties (bending strength and bending stiffness) and termite resistance was also determined. Results showed that extractive content increased in all solvents, lignin and α-cellulose also increased and hemicelluloses decreased. Compounds derived from the thermal degradation of lignin were found in heat-treated wood extractions. Dimensional stability improved but there was a decrease in mechanical properties. Resistance against termites was better for untreated wood than for heat-treated wood, possibly due to the thermal degradation of some toxic extractives.
- Calorific Power Improvement of Wood by Heat Treatment and Its Relation to Chemical CompositionPublication . Domingos, Idalina; Ayata, Umit; Ferreira, José; Cruz-Lopes, Luísa; Sen, Ali; Sahin, Sirri; Esteves, BrunoChemical composition influences the calorific power of wood, mainly due to the calorific power of structural compounds and extractives. Heat treatment changes the chemical composition of treated wood. This work studies the relationship between chemical composition and calorific power improvement by heat treatment. Samples were heat-treated by the ThermoWood process ® for 1 h and 2 h. High heating value (HHV) and chemical composition; lignin, cellulose, hemicelluloses and extractives in dichloromethane, ethanol, and water were determined. The HHV of untreated wood ranged between 18.54–19.92 MJ/kg and increased with heat treatment for all the tested species. A positive linear correlation was found between HHV and Klason lignin (R2 = 0.60). A negative trend was observed for holocellulose, cellulose, and hemicelluloses content against HHV, but with low determination coefficients for linear regression. The best adjust for polysaccharides was found for hemicelluloses content. A positive correlation could be found for dichloromethane extractives (R2 = 0.04). The same was obtained in relation to ethanol extractives with R2 = 0.20. For water and total extractives, no clear positive or negative trends could be achieved. The results showed that the HHV of wood increased with heat treatment and that this increase was mainly due to the increase in lignin content.