Thermal Behavior Of Wood Research Articles

Brushite mineralised Scots pine (Pinus sylvestris L.) sapwood - revealing mineral crystallization within a wood matrix by in situ XRD.

Dicalcium phosphate dihydrate (CaHPO4·2H2O, DCPD, brushite) crystals were synthesised within Scots pine sapwood via a wet-chemistry route from aqueous solutions of Ca(CH3COO)2 and NH4H2PO4 salts. SEM/EDS analysis was used to assess the saturation of the wood cell lumina and cell wall as well as morphological features and elemental composition of the co-precipitated mineral. Brushite mineral crystallization and crystallite growth within the wood matrix was studied by in situ XRD. The chemical composition of the mineral before and after the dissolution was evaluated using FTIR spectroscopy. The overall impact of brushite on the thermal behaviour of wood was studied by TGA/DSC and TGA/DTA/MS analysis under oxidative and pyrolytic conditions. Bending and compression strength perpendicular and parallel to the fibre directions as well as bending strengths in longitudinal and transverse directions of the mineralised wood were also evaluated. Results indicate the viability of the wet-chemistry processing route for wood reinforcement with crystalline calcium phosphate (CaP)-based minerals, and imply a potential in producing hybrid bio-based materials that could be attractive in the construction sector as an environmentally friendly building material.

Physiochemical characterization and thermal behaviour of transparent wood composite

This paper describes the fabrication of large size transparent wood composite (TWC) from longitudinal veneers of three hardwood wood species viz., Populus deltoides (Poplar), Grevillea robusta (Silver oak) and Melia dubia (Melia) based on two-step lignin modification bleaching process and polymer (epoxy resin) infiltration. High optical transmittance of ~83.5%, ~76.7% and ~72.8% was obtained at 550 nm wavelength for TWC prepared using 2 mm thick veneers of Poplar, Melia and Silver oak, respectively. Fourier transform infrared spectroscopy and scanning electron microscopy validate preservation of substantial lignin and successful inclusion of polymer in the wood micro-structure. X-Ray diffraction technique was used for analyzing crystallinity in wood and TWC material. Thermal behavior of wood and TWC was studied using thermogravimetric analysis and differential scanning calorimetry. TWC exhibited low density, good mechanical properties, low thermal conductivity (0.36 W/mK) and good thermal stability.

Possibility of using three invasive non-forest tree species as an alternative source for energy production

Non-woody biomass species have high-energy potentials, which could be used for bioenergy production. Invasive species are species spreading into areas, where they are not native, consequently causing environmental and economic problems. Therefore, the present study evaluated the proximate, ultimate, chemical, and fuel characteristics of wood and charcoal of three invasive non-forest tree species in Saudi Arabia: Calotropis procera, Rhazya stricta, and Phragmites australis, which were compared with the wood of Acacia tortilis, a preferable local fuelwood. All these data were discussed to investigate the possibility of using the invasive plants for energy production. The thermal behavior of wood was analyzed using thermo-gravimetric and derivative thermo-gravimetric methods. Overall, compared with the wood of A. tortilis, the woods of R. stricta and P. australis are suitable for energy production. The charcoal produced from P. australis emitted less nitrogen (N) oxide than that of R. stricta.

Predicting the Thermal Behaviour of Wood During Linear Welding Using the Finite Element Method

A numerical model to simulate the temperature behaviour of wood welding samples during the welding process was developed to understand the influence of material parameters on the welding temperature. A finite element method and the CAST3M software were used to simulate and model the temperature changes during welding of beech wood. This model takes into account the different properties of the wood welded bondline, the geometry of the sample and the external conditions. The energy produced by the friction welding of the wood samples was determined from infrared thermography measurements for the welding process and inputted into the model. The comparison between the predicted and experimental results shows that the model is reliable. The applied pressure, the vibration, the extrusion of material and the chemical reactions, particularly exothermic reactions, are not taken into account in this model and thus probably explain the differences existing between actual and simulated values. However, this numerical simulation gives information on the distribution of the temperature in the sample. The model predicted that the temperature difference between the centre and the side of the sample is not higher than 4°C. This means that the border effects are negligible. The model was tested for different welding times. According to the model a heat flow about 70 kW/m2 is necessary at the welding line to ensure a satisfactory bonding for the chosen sample geometry. Welding of large wood pieces has also been simulated in this study.

Thermogravimetry/mass spectrometry study of woody residues and an herbaceous biomass crop using PCA techniques

The devolatilization behaviour of pine and beech wood from carpentry residuals and an herbaceous product from an energy plantation (artichoke thistle) was investigated by thermogravimetry/mass spectrometry (TG/MS). The effect of three pre-treatments, hot-water washing, ethanol extraction and their combination, was also studied. Principal component analysis (PCA) was employed to help in the evaluation of the large data set of results. The characteristics of the thermal decomposition of the herbaceous crop are considerably different from that of the woody biomass samples. The evolution profiles of some characteristic pyrolysis products revealed that the thermal behaviour of wood and thistle is still considerably different after the elimination of some of the inorganic ions and extractive compounds, although the macromolecular components of the samples decompose at similar temperatures. With the help of the PCA calculations, the effect of the different pre-treatments on the production of the main pyrolysis products was evidenced.

Chemical investigations on the thermal behaviour of wood during friction welding

Friction welding is a new technology in the course of which wood pieces are subjected to circular or linear movements in a welding machine. The wood in the contact zone is heated and melted. Aiming at a better understanding of the thermal alteration of wood and the formation of a viscous layer acting as adhesive, the thermally changed material was taken to be analysed by chemical and spectroscopic methods. As a manifestation of thermally splitting of wood, the total amount of extractable compounds within the joint material (JM) is higher than that of unaltered spruce. Cellulose was found less altered than the other essential wood components. Polyoses, on the other hand, are less stable under the conditions of friction welding; they are detectable only in small amounts in the altered zone. Lignin also suffers distinct changes as demonstrated by the increase of free phenolic groups and the decrease of the typical bonds between the phenolpropane units. Furan derivatives were detected within the volatiles of the smoke gas, arising mainly from the polyoses. It is obvious that reactions between furfural and other furan derivatives with lignin belong to the main reactions in the friction zone leading to cross-linking of the JM.

PREDICTING THE TEMPERATURE DISTRIBUTION OF WOOD EXPOSED TO A VARIABLE HEAT FLUX

Modeling and experimental work on the auto-ignition of wood exposed to variable heat fluxes are presented. A one-dimensional model that describes the pyrolysis of wood subject to a linearly increasing heat flux was developed. Experiments were conducted for three species of wood subject to three levels of heat flux increasing rate. Reasonable comparative results are shown for in-depth temperature distribution. The thermal behavior of wood expose to variable heat fluxes is similar to that under low constant heat fluxes to some extent.

Thermal degradation of wood treated with creosote

The results of investigations on the thermal behaviour of wood, wood treated with creosote, and of creosote are reported. Thermal analysis coupled with ion impact mass spectrometry as well as thermolysis in the modified Bayer-ICI-Shell combustion apparatus (BIS) were applied. The emission products from the BIS-apparatus were analysed qualitatively and quantitatively by gas chromatography coupled with a mass selective detector (GC/MSD). It is shown, that the degradation of creosote and wood treated with creosote is starting with a drying process of the wood around 75°C, followed by evaporation of the creosote compounds between 180 and 400°C. Wood itself is decomposed in an anaerobic process between 300 and 340°C, followed by an oxidative process around 400°C. The oxidative decomposition and mineralisation of creosote takes place between 400 and 600°C with a maximum at 540°C.

Thermal Degradation of Painted Wood. an Experimental Study

A comparative study of thermal degradation of painted and unpainted parti cle board specimens has been carried out. Experiments based mainly on the measurements of piloted ignition delay, mass loss rate and temperature profile have been performed using a radiative heat flux equal to 2.4 W/cm2. Thermo gravimetric analysis has complemented these measurements. It has been shown that thermal degradation of paints produces a solid residue which strongly affects exchange phenomena at the wood surface and consequently the thermal behavior of wood.