Thermal Degradation and Thermal Conductivity of Gypsum-Cement Particleboard

Thermal degradation of boards made from wood particles mixed with gypsum and gypsum-cement was determined in air and nitrogen by thermogravimetric analysis. The pure constituents of the boards (wood particles, gypsum, and Portland cement) were characterized separately. The thermal conductivity of the boards was determined using a heat flowmeter apparatus. Commercial gypsum board was used as a control for all the tests performed. Commercial gypsum board, pure gypsum, pure Portland cement, and gypsum-cement mixture showed mass losses between 18 and 22% at 800°C. Conversely, the wood particles were very sensitive to heat in the presence of air. In general, gypsum-cement particleboard exhibited better resistance to thermal degradation than gypsum particleboard, but it has the highest thermal conductivity as a result of its higher density. Thermal conductivity was shown to be strongly dependent on board density

Moisture Content-Water Potential Relationship of Sugar Maple and White Spruce Wood From Green to Dry Conditions

The moisture content-water potential relationship was determined at 40°C and 60°C for sugar maple (Acer saccharum Marsh.) sapwood and at 60°C for white spruce (Picea glauca (Moench.) Voss.) heartwood from green to dry conditions. The pressure membrane technique was used for high moisture contents and equilibration over salt solutions for low moisture contents. The results show that at high moisture contents, the equilibrium moisture contents obtained from the green condition are lower than those obtained from full saturation (boundary desorption). It is recommended that the sorption history must be taken into account when modeling wood drying. Water potential at a given moisture content increases with temperature. There is a characteristic plateau in the green moisture content-water potential relationship obtained for sugar maple at water potentials between -2,000 and -6,000 J kg-1, which can be attributed to its heterogeneous capillary structure. The maximum concentration of effective pore radius occurs at 0.02 μm in the case of sugar maple, corresponding to the size of the pit membrane openings

Experimental Determination Of The Ratio Of Vapor Diffusion To The Total Water Movement In Wood During Drying

The knowledge of the ratio ϵ of vapor diffusion to the total water movement in wood during drying is necessary when phase change is considered in the heat transfer equation of a wood-drying model based on water potential. An original experimental method was developed to determine the ratio ϵ. The method is based on the measurement of temperature and moisture content profiles in wood during drying and the calculation of total enthalpy profiles.ϵ was determined from drying experiments of red pine sapwood (Pinus resinosa Ait.) in the radial direction at 18, 56, and 85°C. The experimental results show that ϵ increases from 0.15 to 0.5 as moisture content decreases from values close to saturation (160%) to about 15%. ϵ reaches a plateau at about 0.33 for intermediate moisture contents (35 to 120%)

Low velocity impact behaviour of asymmetric three-layer sandwich composite structures with and without foam core

This paper presents an experimental investigation of the impact behaviour of three layer sandwich structures made of high density polyethylene (HDPE) and hemp, with and without a foam core. Low-velocity falling weight and Charpy impact tests were performed to investigate the influence of hemp content, skin thickness and core density. The strength, load, absorbed energy, and deflection histories were recorded and analysed and the damaged specimens were inspected to determine the failure patterns. Based on the Charpy impact results, the structures with foam core had higher energy absorption capabilities compared to their counterparts without foam core. In addition, based on the falling weight impact results the energy dissipation properties of sandwich structures without foam core were superior to the structures with foam core. This property was also greatly influenced by skin fibre content, skin thickness and structure configuration

Physical and mechanical properties of oriented strand board made from Eastern Canadian softwood species

This study aims to investigate the feasibility of producing OSB from softwood species used in the Eastern Canadian softwood lumber industry in the context of the overcapacity of softwood chips traditionally produced for the pulp and paper industry. Balsam fir, black spruce, and jack pine logs were used to make 15 mm thick OSB panels with a target density of 600 kg/m3. The panels were manufactured at a temperature of 210 ◦C during a pressing cycle of 300 s. Strands with different thicknesses were used to obtain a constant specific surface of 6.7 m2/kg for the three species. The bending modulus of the rupture and modulus of elasticity, internal bond, and thickness swelling of the OSB panels were determined and compared to the CSA standard requirements. The species significantly affected the physical and mechanical properties of OSB. The bending properties of OSB decreased with an increase in the species wood density. The internal bond strength of OSB increased with the increase in species wood density. The panels made from softwood species showed physical and mechanical properties exceeding the standard requirements, except for high thickness swelling. The combination of softwood and aspen strands significantly improved the thickness swelling of softwood-based OSB. The reduction in the surface layer density could also be explored to reduce the thickness swelling of the OSB made from the softwoods considered in this study

Determination of Physical and Mechanical Properties of Finishing Papers Used for Wood-Based Composite Products

There has been a noticeable trend in the furniture and flooring industries in using finishing products (decorative paper, foil, wood veneer, and so on) of different quality on both surfaces of raw engineered wood-based panels. Under variable temperature and RH conditions, this practice can result in dimensional instability. The objective of this study was to determine the key properties of five finishing papers affecting the hygromechanical behavior of wood-based composite panels. The diffusion coefficients, swelling properties, and tensile modulus of elasticity (MOE) of the finishing papers were determined. The results show that the finishing papers studied are anisotropic in terms of their physicomechanical properties. For papers impregnated with melamine-formaldehyde resin, the tensile MOE decreases with an increase in resin content. Swelling is the most significant dimensional change. The range of variation of the linear expansion coefficients is between 0.03 and 0.17 in the fiber direction and between 0.08 and 0.28 in the transverse direction for raw papers. The linear contraction coefficients vary between 0.05 and 0.31 in the fiber direction and between 0.07 and 0.28 in the transverse direction. The behavior is different during adsorption and desorption. Effective diffusion coefficients of the papers tested vary between 4.5 × 10-12 and 8 × 10-11 m2s-1

Longitudinal and Transverse Permeability of Balsam Fir Wetwood and Normal Heartwood

The occurrence of wetwood in balsam fir is a problem in the drying of sawn lumber: drying time increases and moisture content of dried lumber is heterogeneous. Permeability may be used as an indicator of drying rates. Longitudinal, radial, and tangential intrinsic permeability of balsam fir wet-wood and normal heartwood was measured in this study. The longitudinal intrinsic permeability was about 2,000 times and 9,000 times higher than the tangential and the radial intrinsic permeability, respectively. Wetwood had a higher longitudinal permeability than normal heartwood, but no significant difference was found between the radial and tangential directions. Sampling height in the tree, basic density, and growth ring width had no effect on the intrinsic permeability. An increase of latewood percentage in the growth rings resulted in an increase in longitudinal intrinsic permeability and a decrease in tangential intrinsic permeability. Radial flow seemed to be controlled by ray blockage in wetwood and normal heartwood, which may result in radial impermeability of wood. A poorly drained stand seemed to favor wetwood formation