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Thermally modified wood is becoming an increasingly popular material for different applications in buildings. Laboratory tests indicated a positive effect of thermal modification on durability, dimensional stability and thermal conductivity of wood. Therefore, windows and facade elements made of thermally modified Norway spruce and non-modified Norway spruce were tested in the field and installed in different test objects which were exposed at five locations in Europe (Slovenia, Germany, Sweden, and Spain). Results from monitoring showed that elements and windows made of thermally modified spruce (TMS) had considerably lower wood moisture content compared to the ones made of non-modified spruce and that wax further positively influenced moisture performance. Colour changes of TMS were more intensive compared to non-modified spruce but were successfully retarded by adding pigments to the wax. Mould and stain growth was largely dependent on the location, amount of precipitation and relative humidity. [ABSTRACT FROM AUTHOR]

The load-carrying capacity of a timber structure is highly dependent on the strength of its connections. Very limited information exists on the thermal degradation, or the properties at elevated temperatures, of such connections. This insufficient information is one of the major impediments for modeling elevated temperature performance for wood-frame structures. The objective of this study was to characterize thermal degradation of yield load capacity of single-shear nailed connections between wood and oriented strand board (OSB) as a function of time and temperature. The mechanism of degradation was explained using first order kinetics. Using the principles of time–temperature superposition (TTS), predictive models for connection capacity degradation were developed. A total of 450 wood-to-OSB connections were tested laterally after exposure to nine different elevated temperature regimes. The degradation of yield load strength over time occurred at a constant linear rate. Temperature dependence of this rate was modeled using the Arrhenius activation energy theory. Using Arrhenius activation energy theory and principles of TTS, a master curve was developed to predict the performance of connections after exposure to a temperature of 150°C. The predictions matched well with independent experimental observations. The master curve developed using TTS provides predictive estimates of residual capacity in a connection as well as its failure times. [ABSTRACT FROM PUBLISHER]

Insulation materials have the potential to alter the fire resistance of timber frame assemblies. At present. Eurocode 5 Part 1-2 provides a model for the fire design of the load-bearing function of timber frame assemblies with cavities that are completely filled with stone wool. An extension of this model for glass wool in a post-protection phase has been published in the European Technical Guideline for Fire Safety in Timber Buildings. However, very little is known about the protection afforded by other insulation materials. This paper provides an overview of a study whereby model scale tests were performed with nine different insulation materials. The results of model scale furnace tests showed that the development of a 300° C isotherm on wood-insulation interfaces could be an indicator of the fire protection given by these insulations. Based on these findings, three different levels of fire protection with batt-type insulation materials are proposed. In this paper the most sensitive parameters that describe the protection against charring given by different insulations are analysed. The study offers some important insights into the concept of a new design model for the fire resistance of timber frame assemblies. [ABSTRACT FROM AUTHOR]

The major aim of this study was to create a numerical model of thermal bridges in a wooden structure and to discover differences between factual values of linear thermal transmittance utilized in the finite-element (FE) modelling and values given by the European normative method (EN ISO 14683). Thermal bridges of wooden structures were detected using thermocamera FLIR S65 for infrared detection. These measurements allow displaying the temperature distribution of the thermal scan and proving the positive correlation between heat flux and change in the evaluated temperatures of a thermal bridge. A three-dimensional FE model of the structure was prepared for the thermal analysis using the engineering software ANSYS Workbench 13. The transmission heat loss coefficients of a prefabricated wooden house were established based on the Czech normative method (ČSN 730540-4). Linear thermal transmittance values calculated from the thermal analysis and the normative method given by EN ISO 10211 were compared. The results show that even if the transmission heat loss coefficients meet the requirements designated by standards, the real heat losses are increased by thermal bridges involved in the construction. Their influence is determined by the linear transmittance value which is usually not exactly established. [ABSTRACT FROM PUBLISHER]

High-temperature heat treatment (HTHT) is an effective method for improving the wood dimensional stability and biological durability at present. However, the quantitative control of the wood color during the HTHT has been a more difficult problem for a long time. To solve the problem of quantitative control of wood color under the thermo-vacuum treatment (TVT) process, the mathematical model of heat and moisture transfer in alder birch wood (Betula alnoides) during the TVT process was built, and its application in the quantitative control of the wood color was also studied. (1) The experimental values and the model values of heat and moisture transfer in wood were found to be in good agreement. (2) The changes of wood temperature and moisture content (MC) were influenced obviously by the heat treatment temperature, the initial MC, and the thickness of specimen as well. The higher the heat treatment temperature was, the more rapid was the rise in the wood temperature and the drop in MC. The higher the initial MC of the wood was and the thicker the wood got, the slower the rise in wood temperature and the drop in MC. (3) Based on the mathematical model of heat and moisture transfer during the TVT process and the wood color index difference regression equations in the function of the temperature and time, the quantitative control of alder birch wood color during the TVT process was achieved. Therefore, it is feasible that heat and mass transfer principle applied during the TVT process guided the wood color quantitative control. [ABSTRACT FROM PUBLISHER]

This article reports a study of flame retardancy and thermal and mechanical properties of wood-plastic composites (WPCs) based on high-density polyethylene and pine flour. The study shows that sample composition plays an important role in WPCs' properties. The influence of additives like fillers (SiO2or CaCO3) and flame retardants ammonium polyphosphate (APP) and pentaerythritol (PER) on WPCs' properties has been considered. The best properties are shown in samples using SiO2as filler and treated with the intumescent fire retardant APP/PER. Such samples have excellent fire retardancy with V-0 rating (UL-94 test) and imply that APP/PER fire retardant ensures effective fire retardancy for WPCs. [ABSTRACT FROM AUTHOR]

Information about several papers discussed at the 10th annual Wood Science & Engineering (WSE) network meeting held in Edinburgh, Scotland on October 13-14, 2014 is presented. Topics include timber engineering, wood technology, and thermal and chemical modification of wood. The meeting featured several speakers including Peter Wilson, Callum Hill, and Peter Wilson.

This study aimed to evaluate physical and mechanical properties and colour changes of fast-growing Gympie messmate wood subjected to two-step steam-heat treatments. To achieve this, Gympie messmate wood was thermally treated under different conditions. Combined steam (127°C and ∼0,1471 MPa) and heat treatments in an oven (180–240°C for 4 hours) were performed. Physical and mechanical properties were evaluated by weight loss, equilibrium moisture content, specific gravity, volumetric and linear swelling and static bending tests, while colour changes were studied using CIEL*a*b*technique. The main findings showed that the steam pre-treatment in autoclave influenced most of the technological properties evaluated, mainly for heat treatments performed in low temperatures (180–200°C). The most significant changes after thermal treatments were observed for dimensional stability, which increased as a function of temperature of treatment. On the other hand, mechanical strength of thermally modified wood was significantly affected, while stiffness did not change. Colour modifications due to the application of two-step steam-heat treatments confirm the possibility to using these samples for aesthetic purposes. [ABSTRACT FROM PUBLISHER]

Radio-frequency (RF) heating has been widely used in the wood industriesand it is essential to understand the factors affecting the heating rates. In this article, Chinese fir (Cunning hamialanceolata) was heated with RF energy intermittently at 2 min per cycle to study the effect of wood moisture content (MC), sample thickness, and RF power level on heating rates. The study revealed that wood MC significantly affected the RF heating rate (p < 0.01). The heating rate was the highest (5.0°C/cycle) at an MC around the wood fiber saturation point (FSP). The heating rates were lower with a lower MC of 15% (0.89°C/cycle) and a higher MC of 70% (1.2°C/cycle). Lumber thickness did not have a significant effect on the RF heating rate at the center of the lumber; however, the heating rates at various locations along the thickness direction were significantly different. The temperature at the lumber center was 20°C higher than the temperature at 10 mm below the surface during heating. The heating rate for lower RF power level was initially greater than the rate at higher power RF level and then rapidly decreased. However, the heating rate at the higher RF power level remained constant during the whole heating process. RF power levels had a significant effect on the internal heating rate of wood (p < 0.01). [ABSTRACT FROM AUTHOR]

The moisture content of wood is known to have a significant influence on the wood's mechanical properties. Using wood as an energy absorber in impact limiters of packages for the transport of radioactive material, it is of particular importance to ensure the moisture content and thus relevant mechanical properties to be in specified limits. The paper surveys the influence of wood moisture content on the mechanical properties of wood. Different measuring methods are discussed with respect to in situ applicability, accuracy and effort. The results of an experimental analysis of the accuracy of hand held moisture metres using the electrical resistance method are discussed. Conclusions are drawn regarding the measurement of moisture content of wood upon delivery as well as of complete impact limiter assemblies. Requirements for quality surveillance during manufacturing of wood filled impact limiters are derived and it is exemplified how to meet them. Construction, manufacturing and inspection of impact limiter encapsulation with regard to leak tightness are addressed. [ABSTRACT FROM AUTHOR]

Two Malaysian hardwoods, acacia (Acacia mangium) and sesendok (Endospermum malaccense), that had been subjected to oleo-thermal modification were studied to determine their sorption isotherm behaviour using a dynamic vapour sorption apparatus. All the specimens were thermally modified using palm oil at three different temperatures (180, 200 and 220°C) and three different times (1, 2 and 3 h). The results showed that there was a reduction in equilibrium moisture content at each target relative humidity due to the heat treatment, but that the two wood species showed different behaviour in this respect. The adsorption isotherms were analysed using the Hailwood and Horrobin model, with excellent fits to the experimental data. The monolayer water and polylayer water were both reduced at a range of relative humidity values of the treated samples, although behaviour between the two wood species differed. Heat treatment resulted in an increase in hysteresis ratio, which was probably due to the increase in matrix stiffness of the cell walls. [ABSTRACT FROM AUTHOR]

The thermal treatment of wood has many benefits such as better dimensional stability and attractive dark color and does not use toxic chemicals. The resistance against biological decay can be improved when wood is not in contact with ground. On the other hand, after thermal transformation, wood becomes more fragile. The changes of the wood properties are related to the modification of the wood composition. During the thermal treatment, the evaporation of the moisture content is not the only event. Volatile extractives are evacuated from the wood, while new products and by-products of different chemical reactions appear. The comparison of the extracts obtained from untreated and treated wood can help to identify thermo-chemical reactions, taking place during the heat treatment. This article presents the analysis by Gas Chromatography-Mass Spectroscopy (GC-MS), High Performance Liquid Chromatography (HPLC), and Thin Layer Chromatography (TLC) of polar and non-polar extracts of untreated and heat-treated North American Jack pine (Pinus banksiana). The study of the impact of maximum heat treatment temperature on the composition of the Jack pine extracts showed that the major part of extractives leaves the wood under 200°C whereas most of the new products appear only above 200°C. While the extractives of the untreated Jack pine are dominated by non-polar components, the thermo-transformation seems to generate mainly polar compounds. However, presence of water vapor increases the portion of polar extractives in wood. Interestingly, an important decrease of concentration of phenolic compounds (such as pinosylvin, pinosylvin monomethyl ether, and pinobanksin) in Jack pine wood was observed between 160-200°C. On the other hand, 4-hydroxy-methylfurfural and vanillin have been identified as compounds generated by the heat treatment above 200°C. The identification of other by-products will be presented in a later paper. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]