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Gonçalves Oliveira Valente da Cruz-Lopes, Luísa Paula
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- 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.
- Liquefied wood as a partial substitute of melamine-urea-formaldehyde and urea-formaldehyde resinsPublication . Esteves, Bruno; Martins, João; Martins, Jorge; Cruz-Lopes, Luísa; Vicente, José; Domingos, IdalinaMaritime pine (Pinus pinaster) sawdust was used to produce liquefied wood by the polyhydric method with acid catalysis. The process was optimized to produce the highest amount of liquefied wood. Wood liquefied at 160ºC for 90 min was used in the adhesion tests. The bond strength of veneer glued with urea-formaldehyde and melamine-urea-formaldehyde resins and several mixtures of liquefied wood with urea- formaldehyde and melamine-urea-formaldehyde wasevaluated by automated bonding evaluation system. With the increase in liquefied wood content the bond strength decreased. Nevertheless for 20% liquefied wood the reduction of internal bond strength is relatively small and still within the minimum standards required. When 70% of liquefied wood is employed there is a significant decrease in bond strength. In conclusion it is possible to use a small amount of maritime pine sawdust liquefied wood as a partial substitute of urea-formaldehyde and melamine-urea-formaldehyde resins in the particleboard production, thus decreasing the formaldehyde content.
- Artificial Weathering of Heat-treated Pines from the Iberian PeninsulaPublication . Esteves, Bruno; Herrera, René; Santos, Jorge; Carvalho, Luisa; Nunes, Lina; Ferreira, José; Domingos, Idalina; Cruz-Lopes, LuísaSamples from the two most common pines grown in Portugal (Pinus pinaster Ait) and Spain (Pinus radiata, D. Don) were heat-treated in industrial facilities in accordance with ThermoWood ® class D. For both species, the variation in surface properties, of untreated and heat-treated wood after artificial weathering from 75 to 750 h, is presented. The analysis included the determination of color, roughness, gloss, and wettability before exposure and after each artificial weathering period. Untreated woods became darker faster, while in heat-treated woods, lightness remained approximately constant until 750 h of artificial weathering. Both untreated and heat-treated wood became more reddish in the beginning of the weathering process, turning greener for longer exposure times. Untreated woods became yellower in the beginning, turning into blueish tones later. Heat-treated wood turned slightly yellower until 750 h of weathering. Gloss decreased for untreated wood with no significant changes in heat-treated wood. Despite the changes, the gloss of both untreated and heat-treated wood converged to similar values. Roughness increased for both untreated and heat-treated woods. Artificial weathering increased the wettability of heat-treated wood.
- Increase of calorific value of two important feedstocks by mild torrefactionPublication . Domingos, Idalina; Ferreira, José; Cruz-Lopes, Luísa; Esteves, BrunoIn the last decades efforts have been made to replace fossil fuels by more sustainable feedstocks for the production of energy. A way to increase the travelable distance of this feedstock is to increase its energy content. The objective of this work was to study the increase in the calorific value of two of the most important wood species in the central region of Portugal, a softwood, (Pinus pinaster Ait) and a hardwood (Eucalyptus globulus Labill.), by mild torrefaction. The treatment was made in an oven during 2 -24 hours and temperatures from 170ºC to 190ºC. Calorific value and insoluble lignin were determined. Results show that there is an increase in the HHV (High Heating Value) of both pine and eucalypt samples (higher in eucalypt) and that the increase is higher for higher treatment times. A good correlation between the amount of lignin and the HHV was found.