Wood Moisture Content Research Papers (original) (raw)

This book is written in Polish language.
This book contains two parts: a theoretical description and tasks. The theoretical part presents knowledge of wood physics, especially: hygroscopicity in wood (e.g. adsorption, wood moisture content, fiber saturation point, equilibrium and maximum moisture content), dimensional changes (e.g. swelling and shrinking), density (e.g. porosity, specific gravity), electrical properties (e.g. electric resistance, electric capacity), heating properties (e.g. thermal conductivity, specific heat, heat of combustion) and acoustic properties of wood. There are a lot of calculation tasks (examples of application) in practical part.

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- Wood Science, Physical properties of wood, Wood Density, Wood Moisture Content

The aim of this research is to evaluate the influence of the moisture content of wood on stress wave velocity, as a nondestructive technique for estimating the mechanical properties of gross cross-section Spanish Scots pine (Pinus sylvestris) lumber for structural use. 26 100 x 150 x 3000 mm pieces from Segovia, Spain, were tested with different moisture content values, from 35,5 to 9%. Measurements of longitudinal stress wave velocity were carried out during the natural drying process by using three commercial portable devices based on ultrasonic, acoustic and vibrational techniques. The results can be summarized as three percentage points of decreasing velocity per percentage point of increased wood moisture content in the range from 11,8 to 21,4%: 0,48% for ultrasonic, 0,50% for acoustic wave and 0,65% for longitudinal vibration.

- by Maderas. Ciencia y Tecnologia
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- Wood Science, Timber, Wood Engineering, Lumber industry

Heat treatment improves some wood properties namely: equilibrium moisture, dimensional stability and durability and mechanical properties. In this study, the heat treatment was applied to woods of three natural species from Brazil: Aspidosperma populifolium (peroba mica), Dipteryx odorata (cumaru) and Mimosa scabrella (bracatinga). The woods were heated in an oven under vacuum and under nitrogen, at 180, 200, and 220°C for one hour. The untreated and heat-treated woods were characterized in relation to equilibrium moisture content, basic density, shrinkage, Janka hardness, and bending MOR and MOE according to NBR 7190 standards. All the thermal rectified woods showed a reduction in the hygroscopic equilibrium content, especially when the heating was under vacuum from 13-15% in the untreated woods to 1-3% for vacuum treatment at 220 °C. The dimensional stability was improved to only a small extent e.g. volumetric shrinkage tended to decrease with increasing temperature. The mechanical properties were affected differently for the three wood species. Heat-treated cumarushowed increased Janka hardness, MOR and MOE; and peroba mica increased MOR and MOE but not Janka hardness; while bracatinga was less influenced by the heat treatment.

- by Maderas. Ciencia y Tecnologia
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- Wood Science, Timber, Wood Engineering, Uso de la Madera

Freshly-felled Chinese fir (Cunninghamia lanceolate), Masson Pine (Pinus massoniana) and Camphor Tree (Cinnamomum camphora) logs were reconstituted to form laminated lumber with moisture content above fiber saturation point by slicing, finger-jointing, gluing, and cold-pressing processes. The laminated lumber was then sliced into wood veneers, which were air-dried to about 15% moisture content. The surface roughness of the veneer was tested in comparison with two commercial engineered wood veneers using a stylus tracing method. The influence of the wood surface roughness was relatively small for the wood species chosen due to their similar densities. All roughness parameter values were consistently larger along the transverse direction compared with these along longitudinal direction. The values of surface roughness at the finger-joint region were higher than these that at the non-finger-joint region along both longitudinal direction and transverse direction. The two engineered wood veneers had surface roughness values noticeably smaller in the longitudinal direction, but their values in transverse direction were comparable and even larger compared with these of the prepared wood veneers including both non-finger-joint and finger-joint regions. Overall, the process of laminating finger-jointed green wood planks and subsequently slicing can be used to yield acceptable wood veneers with sufficient surface quality.

- by Maderas. Ciencia y Tecnologia
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- Wood Science, Timber, Wood Technology, Industrias de la Madera
- by Hamdan Husain
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- Wood Science, Timber, Wood Engineering, Lumber industry
- by Olubukola Oyerinde
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- Wood Science, Timber, Wood Engineering, Lumber industry

Juvenile Neolamarckia cadamba or kelempayan tree has been harvested from forest plantation and converted into sawn timber. Some basic properties of timber such as physical and mechanical were determined from different parts of the tree namely lower, center and upper. The physical properties were evaluated. The mechanical properties were conducted using small test clear specimens. The results indicated that the physical and mechanical properties of the lower portion of the trunk were significantly superior compared to the upper portion of the trunk. The investigation revealed that the wood be able to use as a substitute material of the furniture components after some modification undertaken on its properties.

- by Maderas. Ciencia y Tecnologia
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- Wood Science, Timber, Wood Engineering, Lumber industry

The moisture sorption behaviour of three coating thicknesses of shellac and polyurethane films on Dalbergia sissoo substrate is studied in this paper. The thin films of either coat failed to reduce the water vapour transmission significantly. However, the thick coats were able to reduce this rate illustrating the importance film thickness of coating used on surfaces of wood products. The increment in Moisture Content over the conditioned MC showed a clear film thickness effect in the case of PU with the increments reducing with increasing thickness. The Moisture Exclusion Effectiveness of PU coating showed better values than shellac coating with both the finishes showing a thickness effect. More importantly, the study illustrated the effect of coating thickness even when the differences are small.

- by Maderas. Ciencia y Tecnologia and +1
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- Wood Science, Timber, Lumber industry, Uso de la Madera

Sorption behavior of four tropical woods coming from Cameroon is studied using a Dynamic Vapor Sorption-Intrinsic apparatus. Sorption isotherms at 20°C and 40°C of Triplochiton scleroxylon (obeche), Entandrophragma cylindricum (sapele), Sterculia rhinopetala (lotofa) and Terminalia superba (frake also called limba) are compared to those in the literature with methods using saturated salts for lotofa and frake with satisfactory results. Experimental values are fitted using two sorption isotherm models. Sorption hysteresis is greatest in sapele and least in frake. When temperature increases, differences in the hysteresis of sorption among the woods decreases. Hystereses of all studied woods ranged from 0,5 to 3%. Our studied woods have lower equilibrium moisture content probably caused by the higher values of extractives content. The water sorbed molecules on multilayer during both adsorption and desorption at 20°C and 40°C is greater in the case of frake and lower in the case of lotofa. The water sorbed molecules on multilayer of sapele is greater than those of obeche. The predominance of multilayer over monolayer of our woods is from 0,2 to 0,4 relative humidity in adsorption phase, and from 0,3 to 0,4 relative humidity in desorption phase.

- by Maderas. Ciencia y Tecnologia and +2
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- Wood Science, Timber, Wood Products, Wood science and technology

Drying stress is the main cause for the generation of drying cracks in wood disks during drying, which limits the processing and utilization of this valuable material. For this study, white birch disks with one trunk and a thickness of 30 mm were dried under three different drying conditions: 1) a very slow drying process preventing the generation of a radial moisture content (MC) gradient, 2) a drying process with slowly increasing temperature leading to a radial MC gradient, with a higher MC in the heartwood, and 3) the same heat drying process but the wood disks were partly covered with a thin plastic film prior to the drying process leading to a reversed radial MC gradient, i.e., a higher MC in the sapwood. For each drying condition, the tangential elastic strain in the wood disks was investigated for a mean MC of 26%, 18% and 10%, respectively, as a function of the radial distance from the pith in order to predict the drying stress. Furthermore, the stress characteristics and stress reversal mechanisms in wood disks are discussed in this paper with the help of stress analysis sketches.

- by Yingchun Cai and +1
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- Drying Technology, Wood Science, Timber, Wood Engineering
- by Benedito Vital
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- Materials Science, Wood Science, Timber, Wood Engineering
- by Eva Hermoso
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- Wood Science, Timber, Mechanical properties, Wood Engineering

A method to estimate the surface moisture content below the fibre saturation point that is a function of the surface temperature, wet-and dry bulb temperatures, equilibrium moisture content, and fibre saturation point was evaluated. The method is based on the premise that the surface temperature is solely influenced by the surface moisture content and the climate that the surface is exposed to. The prediction model contends that the surface moisture content is equal to the fibre saturation point when the surface temperature is equal to the wet bulb temperature, and equal to the equilibrium moisture content when the surface temperature is equal to the dry bulb temperature, with a linear interpolation between those two points. The model thus predicts that the average moisture content of a thin piece of veneer can be predicted with fairly good accuracy. Also, when drying boards in a fast changing climate, e.g. fan reversals in industrial kilns, the surface temperature and surface moisture content should change as abruptly as the climate does. Additionally, the surface moisture content should correlate to the known drying phases, with a consistently high surface moisture content during the capillary phase when the wet line is close to the surface, and a quickly decreasing surface moisture content when the wet line moves into the wood during the transition to the diffusion phase. The prediction model was tested in these three scenarios and the results suggest that the basic premise is reasonable, and that the method is useful for surface moisture content estimation.

- by Maderas. Ciencia y Tecnologia
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- Wood Science, Timber, Wood Engineering, Lumber industry

The moisture sorption isotherms of Algerian bay leaves (Laurus nobilis) were determined experimentally in this work. The equilibrium moisture contents of the leaves were measured at 40, 50, and 60 °C using static gravimetric method. Six mathematical models were tested to fit the experimental data of sorption isotherms and predict the hygroscopic behavior during storage or drying. Peleg model was found to be the best fitting model for describing the sorption curves. The net isosteric heat of sorption was computed from the equilibrium data at different temperatures by applying the integrated form of the Clausius-Clapeyron equation. The net isosteric heat of sorption is inversely proportional to the equilibrium moisture content and is found to be an exponential function of moisture content.

- by Maderas. Ciencia y Tecnologia
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- Wood Science, Timber, Wood Engineering, Lumber industry
- by Benedito Vital
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- Wood Science, Timber, Wood Engineering, Lumber industry

Juvenile Neolamarckia cadamba or kelempayan tree has been harvested from forest plantation and converted into sawn timber. Some basic properties of timber such as physical and mechanical were determined from different parts of the tree namely lower, center and upper. The physical properties were evaluated based on MS 837:2006, BS EN 13183-1:2002 and ISO 3131:1975 (E). The mechanical properties were conducted using small test clear specimens following BS 373:1957. The results indicated that the physical and mechanical properties of the lower portion of the trunk were significantly superior compared to the upper portion of the trunk. The investigation revealed that the wood be able to use as a substitute material of the furniture components after some modification undertaken on its properties.

- by Benedito Vital
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- Wood Science, Timber, Wood Engineering, Lumber industry
- by Khairul Masseat
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- Wood Science, Timber, Wood Engineering, Lumber industry

Turkish hazel (Corylus colurna) lumber with a nominal thickness of 5 cm from the Kastamonu region, Turkey, was dried through conventional kiln drying using two different programs, a non-protective drying schedule and a protective drying schedule. The goal of the study was to obtain a kiln schedule that would maintain wood quality and also save drying time until a final moisture content of 8 ± 2% was reached. The intensity of warping (twisting, bowing, cupping, crooking), superficial, internal, and end checks, residual stresses, drying rate, and moisture gradient of the dried woods were measured, and the results were evaluated according to the classification of the European Drying Group. The results showed a more homogeneous moisture profile, fewer occurrences of superficial checks, and an absence of internal checks when using the protective drying schedule due to low warping values compared with those for the non-protective drying schedule. From the point of view of energy efficiency, by saving 60 h of drying time, the non-protective schedule reduced electricity by 960 KWh and was therefore more profitable by $105.60 in this trial. Therefore, it seems that the protective drying schedule should be recommended as the optimum program for drying Turkish hazel lumber from the Kastamonu region at the commercial scale.

- by Maderas. Ciencia y Tecnologia
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- Wood Science, Timber, Wood Engineering, Wood drying