Thermal Properties Of Wood Research Articles

The impact of density, temperature, moisture, and test direction on the thermal conductivity coefficient in pine wood

The article focuses on the study of the thermal properties of pine wood, a material traditionally used in construction, especially in Poland. The trend towards sustainable construction necessitates a deeper analysis of its properties. Due to the insufficient amount of data in the literature on the thermal conductivity of pine wood, detailed studies were conducted taking into account different wood densities. Seasoned wood samples were subjected to various processes and tests, measuring the heat conduction coefficient under different conditions. These results are relevant in the context of sustainable construction and will assist in further research on wood as a building material. The studies also took into account the effects of temperature and humidity on the thermal properties of wood, which is crucial for its application in various environmental conditions.

Thermal properties of wood flour reinforced polyamide 6 biocomposites by twin screw extrusion

Abstract The use of waste wood flour as polymer reinforcements has recently gained popularity because of its environmental benefits. The goal of this research is to determine the thermal properties of a waste wood flour/polyamide 6 composite made via extrusion. The fillers were melt compounded with polyamide 6 at filler concentrations of 5%, 10%, and 15% using a twin screw extruder, followed by compression molding. The processability of waste wood flour/polyamide 6 composite was evaluated using thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), and dynamic thermomechanical analysis (DMA). According to the TGA analysis, the thermal stability of the composites decreases as the natural fiber content increases. The onset temperature of rapid thermal deterioration was reduced somewhat from 425 °C (neat PA6) to 405 °C (15 wt% wood flour). According to the DSC results, the addition of natural fibers resulted in quantify changes in the glass transition (T g), melting (T m), and crystallization temperature (T c) of the PA6 composites. The storage modulus from the DMA study increased from 1177 MPa (neat PA6) to 1531 MPa due to the reinforcing effects of wood flour (15 wt%). Waste wood flour/polyamide 6 composites offer advantageous thermal properties, enabling us to profit from the strengthening potential of such cellulosic reinforcements while remaining recyclable and generally renewable.

Thermal properties of wood: measurements by transient plane source method in dry and wet conditions

Increasing use of wooden material in new constructions and retrofit activities push to a deeper comprehension of properties and specifically thermal properties of different wood species. On one side wooden products on the market are accompanied by few and generic information on the other side analysis of literature confirms a lack of experimental data on thermal conductivity of wood species grown in Italy. In this paper some species of softwood like spruce and larch, and hardwood, like elm, oak and ash are analysed and their thermal conductivities as a function of the equilibrium water content are evaluated by the use of a transient plane source. Results are in line with literature values and, in general, conductivity augments with water content increasing. The relationship between water content and conductivity exploited a linear behaviour for all species.

Physical, and Thermal Properties of Wood Impregnated with a Mixture of Furfuryl Alcohol, Styrene, and Nanoclay

In this study, raw wood (RW) samples were impregnated with a mixture of furfural alcohol (FA), styrene (ST), and nanoclay of varying concentration of FA and ST. These impregnated wood and RWsamples were then subjected to FTIR, water uptake (WU), and thermal studies. The FT-IR results at 1600-1800 cm-1showed that the ST/FA/clay-WPNCs had different peak numbers with different positions compared with the RW. So, there was an interaction between RW, FA, ST and clay. The WU of ST/FA/clayimpregnated wood is lower than RW. In thermo gravematric result, below 100 °C the impregnated wood samples had less weight lost compared to RW.

Uticaj različitog sadržaja vlage na termalna svojstva drva

Moisture content is one of the most important properties of wood. The primary purpose of this paper is to examine the dependence between thermal properties and different moisture contents of softwood, hardwood and medium hardwood samples with dimensions of 100 x 100 mm and a thickness of 10 mm (measured using the transient method). Different moisture contents of the wood samples under consideration were achieved by a gradual drying treatment in the laboratory setting. The final results obtained represent the arithmetic means computed from ten sets of measurements. The measured relationship between the thermal conductivity and the mass specific heat of the wood samples was found to indicate an increasing trend, whereas the relationship between the thermal diffusivity and the moisture content of the wood samples showed a non-linear decreasing trend. On the basis of the results obtained, it can be concluded that the thermal properties of wood are greatly affected by the type of wood and changes in the wood moisture content, which mainly depend on wood structure and water conduction in wood.

The Basic Technology of Steaming and Drying of Wood

Drying is a complex heat and mass transfer process which is affected by operating parameters environment and thermophysical properties of wood. Basis for classification of methods of drying is a method of transmission of heat to material. The basic method of drying is convective, but it is accompanied by a conductivity of wood (from the material surface to its center) and thermal radiation. The research investigates the processes of initial heating and steaming of beech wood in the form of profile pieces, which describes the dynamics of change in temperature of wood in general and particularly of surface and inner layers of wood, as well as changing the thermal properties (coefficients of heat-conducting, diffusivity and specific heat capacity) of wood. The change of thermal properties of wood causes the change of heat-exchange criteria of Fourier and Nusselt. So the use of differential equalization of heat-conducting of Fourier is possible only for the certain period of process of heating. Firstly, experimental studies of process of drying of profile workpiece (firewoods) are undertaken with a previous steaming and without a previous steaming; the corresponding sizes of speed of drying, coefficients of moisture conductivity and output of moisture are found. Consequently, taking into account the criterion of Reynolds the coefficient of drying and mass transfer coefficient of Fourier and Nusselt it is possible to synthesize the physical-mathematical model of process of drying. In the course of the study we have elaborated the structure of technological process of drying of firewoods. It is proved to include such successive technological operations as the initial heating, steaming, drying, that allows considerably to intensify mass transfer processes and, to the eventual result, shorten duration of process of drying on 25 % and accordingly to economize the charges of thermal energy. As a conclusion the author proposes structure of the technological process of drying wood that involves the use of environmentally-friendly drying agent for heating and steaming, and drying process steam-air mixture received from the combustion of waste wood. In general, the structure provides an energy saving of realization of technological process and reduces its overall duration.

Synergistic effect of silica sol and K2CO3 on flame-retardant and thermal properties of wood

In this study, silica sol (SiO2 sol) and K2CO3 were used as flame retardants for wood. The synergistic effect of SiO2 sol and K2CO3 on the flame retardancy, leaching resistance, and thermal properties of wood was investigated. The limiting oxygen index results revealed a significant improvement in the flame retardancy and leaching resistance of the wood sample treated with K2CO3 and SiO2 sol using the double bath technique. The thermal analysis results showed that the synergistic effect of K2CO3 and the SiO2 sol effectively prolonged the degradation of the wood sample during the charring stage and improved the stability of the char residue. The thermogravimetry–mass spectrometry analysis and scanning electron microscopy results showed that K2CO3 catalyzed the degradation reaction of the wood sample at lower temperatures resulting in an increase in the water and carbon dioxide output, and the SiO2 sol formed a compact and melted barrier on the surface of the char residue, which hindered the transfer of heat and combustible gases in the condensed phase. Thus, the combination of K2CO3 and SiO2 sol proves to be a promising flame-retardant system for wood.

An Investigation of the Kinetics and Oxidative Thermodegradation Properties of Waste Telephone Pole Samples Treated with Metal Salts

In the present study, combustion mechanisms, activation energy, and exponential constants were investigated for natural pine and acid copper chromate impregnated telephone pole. Oxidative thermodegradation was carried out in air environment at different heating rates by using thermogravimetric analysis. In order to calculate thermal kinetics, the Coats Redfern method was used. There were less flammable products, lower weight losses in the main oxidation region, a decrease in the maximum weight loss temperatures, and more char formation for treated samples as compared to untreated samples. In other words, due to treatment of wood with acid copper chromate, thermal properties of wood changed.

Quasi-Stationary Measurements of Lignamon Thermal Properties

Thermal properties of wood and modified wood-based materials are important parameters that influence the manufacturing process and final industrial utilization. The aim of this work was to investigate three main thermal properties (thermal conductivity, thermal diffusivity, and specific heat capacity) of ammonia-treated compressed beech wood (Lignamon material) and natural beech wood (Fagus sylvatica).These properties were measured based on the quasi-stationary method developed at the Department of Wood Science at the Technical University in Zvolen. The influence of increased density (caused by ammonium treatment and compression) of four different types of Lignamon material on the thermal properties was discovered, and the results were compared with those from untreated beech wood. The results confirmed a dependency on the density of the material. With increasing Lignamon compression extent (increasing density value), the thermal conductivity increased and the thermal diffusivity decreased. The maximum value of thermal conductivity reached (0.26 W.m-1.K-1 at 1070 kg.m-3) in the case of Lignamon 6k and (0.26 W.m-1.K-1 at 950 kg.m-3) in the case of Lignamon 7n.

Thermal and decay-resistance properties of tropical wood–plastic composites

This investigation concerns about the thermal and decay resistance properties of tropical wood polymer composites. Wood polymer composites were prepared from several types of tropical wood species by impregnating the woods with ethyl methacrylate that was combined with a cross-linker, hexamethylene diisocyanate. Thermal properties of wood polymer composites in terms of thermogravimetric analysis and differential scanning calorimetry were evaluated, and an improvement in thermal stability was found on ethyl methacrylate and ethyl methacrylate–hexamethylene diisocyanate treatment. A significant improvement in decay resistance was also identified in wood polymer composites that were treated with ethyl methacrylate, and also, with ethyl methacrylate–hexamethylene diisocyanate. The improvement in properties was observed as more potential with ethyl methacrylate–hexamethylene diisocyanate combination rather than ethyl methacrylate.

Thermal behaviors and transitions of wood detected by temperature-modulated differential scanning calorimetry

The thermal properties and transitions of solid and ground wood samples conditioned at different humidity conditions were investigated by temperature-modulated differential scanning calorimetry. A time-dependent transition was detected as an endothermic peak in the total and non-reversing heat flows and as a step change in the reversing heat flow during the first heating run of samples with moisture contents above 5 %, but it disappeared in the second heating run. These different thermal behaviors indicate that the effect of heat and moisture on the thermal properties of wood is history dependent. This step change in the reversing heat flow is considered to be a glass transition of moist wood. Other relaxation processes (e.g., enthalpy relaxation) occur simultaneously with this glass transition. The temperature ranges of the transition and the relaxation decreased drastically as the moisture content increased up to 11 %, while they remained almost constant at higher moisture contents. In addition, the transitions of the ground wood occurred at lower temperatures than those of the solid wood at similar moisture contents. Kissinger plots revealed that the apparent activation energy for the glass transition of the solid wood with a moisture content of 11 % was about 600 kJ/mol, whereas that of the ground wood was 220 kJ/mol.

Effects of nanoclay and coupling agent on the physico‐mechanical, morphological, and thermal properties of wood flour/polypropylene composites

AbstractThis article presents the effects of coupling agent and nanoclay (NC) on some properties of wood flour/polypropylene composites. The composites with different NC and maleic anhydride grafted polypropylene (MAPP) contents were fabricated by melt compounding in a twin‐screw extruder and then by injection molding. The mass ratio of the wood flour to polymer was 40/60 (w/w). Results showed that applying MAPP on the surface of the wood flour can promote filler polymer interaction, which, in turn, would improve mechanical properties of the composite as well as its water uptake and thermal stability. Composite voids and the lumens of the fibers were filled with NC, which prevented the penetration of water by the capillary action into the deeper parts of composite. Therefore, the water absorption in composites fabricated using NC was significantly reduced. Scanning electron microscopy has shown that the treatment of composites with 5 wt% MAPP, promotes better fiber–matrix interaction, resulting in a few numbers of pull‐out traces. In all cases, the degradation temperatures shifted to higher values after using MAPP. The largest improvement on the thermal stability of composites was achieved when NC was added. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Thermochemical modeling of isothermal carbonization of thick wood particle – Effect of reactor temperature and wood particle size

A numerical study of isothermal carbonization of thick wood particles has been developed. The proposed model takes into account the heat and mass transfer and chemical kinetics simultaneously. The thermal properties of wood are considered to be linear functions of the local temperature and have been estimated from literature data or by fitting the model with experimental data. The carbonization process has been described by a kinetic scheme based on a two stage semi-global kinetic model developed in a previous work of the authors. The mathematical formulation leads to a coupled nonlinear partial differential equations system, which has been solved iteratively by an implicit finite differences method. The residual mass as well as the temperature profile inside the thick particle are predicted numerically. The obtained results are in good agreement with the available experimental data. Then, the model is used to study the effect of reactor temperature and particle size on the evolution of the local temperature and mass loss inside the wood particle.

Full scale experiments for evaluating theoretical fire wall models

AbstractThe aim of the research described in this paper was to provide experimental results for the evaluation of theoretical models for predicting the behaviour and time‐to‐failure of loadbearing and non‐loadbearing wood framed walls in fire. References for thermal and mechanical properties of wood and gypsum board are given to provide comprehensive input for the evaluation of theoretical wall models. The scope of the research involved full‐scale uninsulated cavity walls with well‐controlled clearly known conditions including initial ambient vertical load capacity for benchmarking the reduction in capacity and stiffness, rotational stiffness of supports, eccentricity of vertical load, elastic moduli of wood and gypsum board in compression, stiffness of slip between gypsum board and studs and end stud effects. The experiments were repeated and they demonstrated that the controls led to high consistency in the results despite the inherent large variability of the mechanical properties of wood. The results include temperature distributions, initial vertical load capacity, load‐deflection plots and times‐to‐failure. The results show that the temperatures in the studs are approximately uniform until all the moisture is vaporized. Thermal properties of wood will not vary significantly for consistent density, moisture content and species of wood. The main structural actions that should be modelled for different loading regimes are deduced. Copyright © 2004 John Wiley & Sons, Ltd.

A Parametric Study on the Time-to-Failure of Wood Framed Walls in Fire

A model has been developed for predicting the time-to-failure of gypsum board clad wood framed walls exposed to fire. This model was developed for designing wood framed walls in accordance with new performance-based building fire codes being introduced around the world. The model has been used to undertake a parametric study of the effects of a wide range of variables on the time-to-failure due to structural collapse. The study found that the most dominant variables in building construction in descending order of importance are depth and breadth of stud sections, fire temperature, thickness of gypsum board, elastic modulus of wood in compression, enthalpy of gypsum board (that is the product density and specific heat) and vertical load. Variations in the thermal properties of wood do not dominate the influences affecting the time-to-failure. The study supports the component additive method for estimating the fire resistance of walls.