Influence of temperature of thermal treatment on surface densification of spruce

Spruce (Picea abies L. Karst) wood lamellae, thermally treated at 170, 190, 210 and 230 °C were surface densified by compression at a temperature of 150 °C to three degrees of compression. Immediate springback, set recovery, mechanical properties in 3-point flexure, Brinell hardness and density profiles measurements were used to determine the effect of thermal treatment on the properties of surface densified wood. The highest immediate springback occurred in wood specimens thermally treated at the highest temperature (230 °C) and decreased with decreasing thermal treatment temperature. The untreated samples had the highest set recovery, which decreased with the temperature of thermal treatment. The surface densification increased hardness and bending strength. The highest increase was in the case of untreated wood and decreased with the temperature of thermal treatment. The modulus of elasticity (MOE) and modulus of rupture (MOR) of surface densified wood decreased with increasing thermal treatment temperature. The trend was similar for specimens which were thermally treated but not surface densified. Surface densification increased the density of the specimens in the first few millimetres below the surface. The highest density was achieved in untreated specimens and the lowest in specimens thermally treated at the highest temperature.     

Effect of grain orientation and surface wetting on vertical density profiles of thermally compressed fir and spruce

The effects of grain orientation and surface wetting on wood densification by compression in a hot press were evaluated for two commercial Canadian wood species, balsam fir (Abies balsamea) and black spruce Picea mariana. The vertical density profiles (VDP) of wood densified at 180 °C could be engineered to achieve different properties depending on press closing rate, wood permeability and annual ring orientation. The lower permeability of spruce caused it to split frequently during hot pressing. For balsam fir, at a press closing time of 2 min, the compressed wood with an original grain angle of 0° (radial compression) shows widened high density bands due to collapse of low density earlywood adjacent to the dense latewood. All grain orientations show higher density areas close to the wood surfaces similar to those of wood-based composites. However, when wood was preheated without pressure for 5 min followed by a press closing time of 2 min, water migrated to and plasticized the board centre causing it to be densified while the surface density remained low. Wood surface plasticizing with water or urea solution causes some localized surface densification, but the effect was not great.     

Measurement of wood grain angle, moisture content and density using microwaves

In many wood products manufacturing processes, it is important to ensure that the physical properties of the raw material lie within acceptable ranges and are measured reliably. It is also important for practical use that the measurement process is robust, low-maintenance, fast and preferably non-contacting. This paper describes the development and demonstration of a microwave system for simultaneously identifying wood grain angle, moisture and density. The method involves propagating a microwave beam through the wood and measuring the resulting depolarization, attenuation and phase shift. The wood physical properties can then be identified from these measurements. In a series of measurements, the prototype microwave system successfully identified wood grain angles for hemlock and Douglas fir respectively with standard errors of 0.9° and 2.5° (measured range = -90° to +90°), moisture content 1.2% and 1.9% (measured range = 7–28%), moisture density 3.7 kg/m³ and 7.9 kg/m³ (measured range = 40–150 kg/m³, and dry density 16 kg/m³ and 30 kg/m³ (measured range = 325–625 kg/m³).     

Thermal properties of wood-gypsum boards

Transient simultaneous measurements of thermal conductivity, volume heat capacity and thermal diffusivity of laboratory wood-gypsum boards have been performed with ISOMET 2104 at room temperature. The influences of wood particle content, density and moisture content on thermal properties were investigated. The measurements were performed in a direction perpendicular to the board plane. The effect of density and wood particle content on the thermal properties may be related to the presence of voids both between and inside particles. It seems, that the dominant mechanism of heat transfer across the board is the heat conduction through the voids. Wood-gypsum boards with a density of 850–1300 kg/m³, a moisture content of 2–11% and a wood particle content of 0–35% have the following thermal conductivity of 0.189–0.753 W m^-1 K^-1, volume heat capacity of 0.683–1.43×10⁶ J m^-3 K^-1 and thermal diffusivity of 0.171–0.367×10^-6 m² s^-1; their magnitudes are higher than those ones of OSB, MDF, particleboard and plywood.     

Thermal transition and thermo-physical properties of potato (<Emphasis Type="Italic">Solanum tuberosum L</Emphasis>.) var. Russet brown

Potatoes are an important food in many regions of the world and are commonly used in a variety of food products. Thermal transition and thermo-physical properties of potatoes are important in order to design efficient food processes and select appropriate storage conditions. In this study, we determined the thermal transitions and thermophysical properties of raw and blanched/par-fried potato for a temperature range of ??32 to 21.1 °C. Using differential scanning calorimetry, we found an initial freezing point (T_f) at ??1.8?±?0.1 °C, an onset of melting (T_m^′) at ??9.9?±?0.2 °C and an unfreezable water content (X^′_w) for maximally freeze-concentrated raw potato at 0.21 kg water/kg potato. Corresponding values for blanched/par-fried potatoes were ??0.9?±?0.1 °C, ??11.0?±?0.2 °C and 0.18 kg water/kg potato. Results show that an increase in solids content decreased T_f of both raw and blanched potatoes. We modelled the relationship between them using the Chen model. The apparent specific heat (C_app) increased around T_f to 31.7?±?1.13 kJ/kg K for raw potato and 26.7?±?0.62 kJ/kg K for blanched/par-fried potato. For frozen raw potato at ??32 °C, thermal diffusivity (α) was 0.89?±?0.01?×?10?^?6 m²/s and thermal conductivity (k), 1.82?±?0.14 W/m K, respectively. These values were higher for frozen raw potato than for the unfrozen raw potato (0.15?±?0.01?×?10?^?6 m²/s and 0.56?±?0.08 W/m K, respectively at 21.1 °C). The apparent density (ρ) of frozen raw potato (992?±?4.00 kg/m³ at ??32 °C) was less than that for unfrozen raw potato (1053?±?4.00 kg/m³ at 21.1 °C), and a similar trend was obtained for blanched/par-fried potato (993?±?2.00 kg/m³ at ??32 °C and 1188?±?7.00 kg/m³ at 21.1 °C, respectively). This study established a correlation between thermo-physical properties and temperature. Findings may be used to inform the design and optimization of freezing processes and frozen storage for potato products.     

Influence of temperature on the embedding strength

In order to determine the influence of the temperature on the embedding strength at the yield threshold, 150 tests were carried out using 8 mm dowels. The tests were performed on samples of Pinus sylvestris L. with density in the range between 489 kg/m³ and 679 kg/m³ with an initial moisture content of about 11%. The tests were carried out in the longitudinal and transversal directions to the wood grains, with the temperature varying from 20°C to 240°C. The tests and the specimen dimensions follow the standard NF-EN 383.     

Proposal for visual grading criteria of structural timber of sweet chestnut from Spain

Bending strength, modulus of elasticity and density were obtained for 981 specimens of Spanish Sweet Chestnut (Castanea sativa Mill.) sawn timber from five provenances. Four-point bending tests were made with three sizes (40 × 100 × 2,500, 40 × 150 × 3,500 and 70 × 150 × 3,500 mm) according to EN 408 (CEN EN 408:2011). Visual grading criteria were established, resulting in 82 % of the samples being classified as one structural quality, namely MEF. Characteristic values of the density and the mechanical properties were determined according to EN 384 (CEN EN 384:2010a): E _0,mean  = 12.3 kN mm^?2; f _m,k  = 28 N mm^?2 and ρ _k  = 510 kg m^?3. Therefore, a strength class D24 was assigned according to EN 338 (CEN EN 338:2010b). The relationship between the modulus of elasticity and bending strength was lower (R² = 0.26) than for Spanish coniferous species.     

Wood–water relations of chestnut wood used for structural purposes

Hygroscopic properties and water vapour permeability of chestnut (Castanea sativa Mill.) wood were studied using saturated salt solutions, and the results were analyzed using the Hailwood–Horrobin model. At 20 °C/65 % the equilibrium moisture content (MC _eq ) and density were 11.5 ± 0.1 % and 576.6 ± 10.2 kg m^?3, respectively, and the fiber saturation point was 20.83 %. The average water vapour permeability was 0.320 kg m^?1 s^?1 Pa^?110⁸, lower than that of Radiata pine (0.726 kg m^?1 s^?1 Pa^?110⁸). Furthermore, there was no difference in permeability between tangential and radial cuts. This low permeability is explained by the scant development of the multilayer of the Hailwood–Horrobin model. This is attributed to the wood extractives, which reduce the void space and hindered condensation. Chestnut wood has different vapour sorption and vapour permeability than conifers normally used in construction.     

Development of selectively densified surface laminated wood based composites

An attempt was made to develop selectively densified surface laminated wood based composites. Two types of wood composites were produced (veneer laminated Medium Density Fiberboard, MDF and wafer overlaid particleboard, PB) in this study. Veneer or wafer plasticized by NaClO₂ treatment and PF resin impregnated were laminated on both sides of the MDF or PB and compressed at ordinary pressure. The main observation was that overlaying plasticized veneer on MDF before hot pressing is a promising method for improving mechanical properties and dimensional stability of commercial MDF. The MOR and MOE of surface laminated MDF attained 177 MPa and 18 GPa, respectively. The water absorption percentage of laminated MDF decreased from 160.7 to 7.2%. Furthermore, it is interesting to note that NaClO₂ treated and resin impregnated wafer or powder laminated particleboards showed excellent performance especially in stiffness. The MOR and MOE reached 40 MPa and 7 GPa which is more than two times higher compared to untreated wafer laminated board and three times higher than particleboard. This value is comparable to commercial lauan plywood having a density of 0.78 g/cm³. The processing technique of the composite is simple and can be easily applied by the industry.     

Fungal and termite resistance of wood treated with 4-methoxytrityl tetrafluoroborate

This study evaluates the decay and termite resistance of Scots pine (Pinus sylvestris L.) treated with 4-methoxytrityl tetrafluoroborate (MTFB). Decay resistance tests of unleached samples showed that 2%, 1.5% and 1% concentrations of MTFB (15.4 kg/m³, 11.1 kg/m³, and 7.4 kg/m³, retention levels, respectively) gave less than 2% decay of Postia placenta and concentrations of 2% and 1.5% less than 2% decay of Coniophora puteana. Wood specimens treated with 4-methoxytrityl tetrafluoroborate solutions were not protected against the brown rot fungi after a 14-day severe leaching process, suggesting excessive leaching of the chemical from wood. Treatment with 2% concentration protected against subterranean termites, Coptotermes formosanus Shiraki based on mass losses in both leached and unleached wood specimens in comparison with lower concentration levels. These results suggest that 4-methoxytrityl tetrafluoroborate might be promising to protect wood being used outdoors against termite attack. However, 4-methoxytrityl tetrafluoroborate did not protect wood against fungal decay. Field tests are needed to observe the performance of 4-methoxytrityl tetrafluoroborate treated wood in ground contact.     

In situ density estimation of timber pieces by drilling residue analysis

Density values are essential for the characterization of wood elements in existing structures. A new method for the in-situ density estimation of timber pieces is proposed based on weighting the residue generated by conventional drilling. This research includes the design and development of a residue collector device coupled to a conventional drill and testing on four Spanish coniferous species: Laricio pine, Scots pine, Radiata pine and Maritime pine (Pinus nigra Arn., Pinus sylvestris L., Pinus radiata D. Don. and Pinus pinaster Ait., respectively). For each species, 44 specimens (except Scots pine, with 42) 60?×?90 mm cross-section and 150 mm length (half radial and half tangential orientation) were tested. Specimen density was obtained by mass/volume ratio. Three 8 mm diameter 46.5 mm deep holes were drilled in each specimen using a brad point bit. The drilling residue was weighed and density was calculated as a ratio to bore volume. Although only slightly smaller, residue density statistically differs from average specimen density. But the specimen density can be inferred by the correlation, statistically significant, with residuals drilling density (R²?=?80.7%) and even better with residual drilling mass (R²?=?84.4%).     

Wood density and annual growth variability of <Emphasis Type="Italic">Picea abies</Emphasis> (L.) Karst. growing in the Ukrainian Carpathians

The purpose of this study was to increase knowledge of the variability of wood density and annual growth of Norway spruce growing in the Ukrainian Carpathians. The material consisted of 21 trees which were cut between 600 m and 1200 m asl from south-west and north-east expositions of the mountain Dovshka. The ovendry and relative wood density increased from the bottom (630 m asl) to the top (1190 m asl) of the mountain and was related to increasing number of tree rings in 1 cm, whereas the width of annual rings decreased expressively. Three significant categories of altitude (forest types) of Norway spruce timbers were estimated for the mountain forest stands. The highest average ovendry wood density (413 kg m^?3) and number of tree rings in 1 cm (17.1) were characterized by spruce trees growing at the wet rocky bilberry spruce forest (above 1000 m asl). Wood density and annual growth are two variables which were significantly correlated with each other and the altitude (R = 0.5–0.6).     

Moisture movement in wood polypropylene composites

Moisture movement in an extruded wood polypropylene composite was evaluated by exposure to high humidity and immersion of the material in both fresh and seawater. The saturation moisture content was approximately 20 and 19% when exposed to distilled water and seawater, respectively. The moisture diffusion coefficient (D _m) of thin specimens exposed to high humidity was 3.4?×?10^?8?cm² $ / $ s. The D _m of small cubic specimens with extruded surfaces removed submerged in distilled water and seawater were estimated to be 3.1 and 2.3?×?10^?8?cm² $ / $ s, respectively. Use of these diffusion coefficients overestimates the rate of moisture movement in larger extrusion profiles indicating the role of transport phenomenon other than diffusion.     

Sorption of ethyl acetate and d‐limonene in poly(lactide) polymers

Poly(lactide) (PLA) polymers have garnered increased attention in the last few years as food packaging materials because they are environmentally friendly polymers. As the production of PLA increases and price per pound drops, PLA is becoming a growing alternative as a green food packaging material. In this research, the organic vapor barrier properties of commercially available PLA polymers were studied. Gravimetric sorption tests in PLA films were carried out, and the diffusion (D), solubility (S) and permeability (P) coefficients for ethyl acetate and d‐limonene in PLA were determined. For ethyl acetate, values of P = 1.22 × 10^?17 kg m m^?2 s^?1 Pa^?1, D = 2.63 × 10^?15 m² s^?1, and S = 4.62 × 10^?3 kg m^?3 Pa^?1) at 45 °C and a partial pressure of 12 654 Pa were obtained. For d‐limonene, no trace was detected after 21 days of testing at 45 °C and 258 Pa, which indicates a permeability coefficient lower than 9.96 × 10^?21 kg m m^?2 s^?1 Pa^?1. Poly(lactide) polymers demonstrated good aroma barrier to ethyl acetate and d‐limonene, and will most likely be good aroma barriers. PLA is not likely to promote flavor loss by either permeation or scalping. Copyright © 2005 Society of Chemical Industry     

Fire-retarding properties of nanowollastonite in MDF

Effects of wollastonite nanofibers on fire-retarding properties of medium density fiberboard were studied. Nanowollastonite (NW) was applied at 5, 10, 15, and 20 g/kg dry weight basis of wood fibers and compared with reference specimens. Two application methods of NW were used: surface application (SA), and internal application. Density was kept constant at 670 kg/m³ for all treatments. Specimens of 150 × 130 × 9 mm³ were prepared and fire-retarding properties were measured using two devices: slide fire test device and fixed fire test device. The properties included: weight loss, ignition and glowing times, width and length of the burnt area, and fire endurance. The obtained results indicated that most fire-retarding properties were significantly improved with the increase in NW-content up-to 15 %, including weight loss, ignition and glowing times, and fire endurance. Higher amounts resulted in decreasing of the properties which was partly due to the less fiber-content, and partly due to the absorption of resin by the wollastonite nanofibers. It can be concluded that SA of NW is more effective in improving fire-retarding properties of medium density fiberboard. Furthermore, 10 % of NW is recommended as an optimum level of consumption.     

Comparison of the modeled potential yield versus the actual yield of maize in Northeast China and the implications for national food security

A precise spatial knowledge of potential yield and actual yield is crucial to assessing an increase in grain yield and is relevant to national food security. In this paper, the potential maize yields at the county level in 2013 in Northeast China were estimated using a Miami model in combination with an integrated fertility index and the effect of chemical fertilizers on yield increase. Then, the spatial characteristics of the climate, farmland and grain production potential were presented, and the potential yield increase and food security implications were analyzed. The estimated production potentials of the climate, farmland and grain in 2013 were approximately 4.65?×?10³–13.06?×?10³ kg/ha, 2.77?×?10³–9.38?×?10³ kg/ha, and 2.97?×?10³–12.1?×?10³ kg/ha, respectively, whereas the actual maize yield in 2013 was 1.50?×?10³–8.60?×?10³ kg/ha, accounting for 41.86–95.84 % of the grain production potential. The total average potential maize increase in Northeast China was 3.32?×?10³ kg/ha, measured from the difference between the climate production potential and the actual yield. Furthermore, the main regions with lower surplus production but a higher potential for increase were located in the eastern Liaoning, Jilin and Heilongjiang Provinces. In addition, the surplus production, which was 136.56 million tons, could feed 341.4 million people in other areas of China. In conclusion, we suggest that improving access to agronomic practices (such as fertilizer and high-yielding seed) and developing agricultural policies and strategies could increase the maize yield and further narrow the yield gap.     

Modeling engineering characteristics of hazelnut kernel during infrared fluidized bed drying

In this study, a laboratory scale infrared fluidized bed dryer was used to dry the hazelnut kernels. The drying experiments were performed under the following drying conditions: air temperatures of 45, 65 and 85?°C, air velocities of 1.30, 3.09 and 4.87 m/s and infrared powers of 500, 1000 and 1500 W. Maximum and minimum values of effective moisture diffusivity for hazelnut kernels were obtained 1.87?×?10^?9 and 1.75?×?10^?10 m²/s, respectively. Activation energy was obtained between 33.02 and 50.22 kJ/mol. Specific energy consumption of hazelnut kernels was obtained between 1.72?×?10³ and 2.23?×?10⁴ MJ/kg. Six mathematical models were used to predict the drying behavior of hazelnut samples. Among these models, the Midilli model sufficiently fitted the experimental drying data. The shrinkage values were obtained within the range of 0.10 and 0.24. The results obtained showed that the \({{L}^{*}},\) \({{a}^{*}},\) \({{b}^{*}}\) and \(\Delta E\) color values of the kernels were significantly affected (P?<?0.05) by air temperature. The highest color changes were related to the air temperature of 85?°C at all air velocities and infrared powers. Maximum values of energy (103.57 N mm) and force (129.84 N) at initial rupture point was related to air temperatures of 85?°C and infrared powers of 1500 W. Minimum values of energy (16.47 N mm) and force (31.74 N) at initial rupture point was related to air temperatures of 45?°C and infrared powers of 500 W.     

Softwood heating in radio frequency fields

The aim of this study was to investigate the heating rate of lodgepole pine (Pinus contorta) and western red cedar (Thuja plicata) during radio frequency (RF) heating. Wood specimens (40 × 150 × 1000 mm³) with various moisture content and power density were heated using a laboratory size RF dryer at a frequency of 40.7 MHz, until shell temperature reached 56?°C that is approved as a lethal temperature for phytosanitation. Heating rate was positively correlated with power density and negatively correlated with moisture content. The ratio of heating rate to power density had a negative correlation with moisture content and density in both pine and cedar. The regression lines for moisture content had good coefficient of determination (R ²) values of 0.63 and 0.61?°C?m³/min kW (pine), 0.50 and 0.55?°C?m³/min kW (red cedar) in both shell and core, respectively. The results demonstrate that the ratio of heating rate to power density is a useful parameter to estimate heating rate. The derived empirical equations made possible the calculation of the heating rate within test conditions applied to this study. The initial temperature rise in shell and core allowed a rather accurate determination of local power density. One dimensional mathematical model to describe the heating rate of wood during RF heating that was derived from the governing heat transfer equation combined with internal heat generation was developed and verified. The model using local power density had high R ² of 0.71 and 0.93 in both shell and core, respectively, indicating that the model was able to predict heating rate of wood with various moisture content under the known power density distribution.     

Influence of dipping time on uptake of preservative solution, adsorption, penetration and fixation of copper-ethanolamine based wood preservatives

Copper-ethanolamine based wood preservatives are the most important products for protection of wood in use class III and IV applications. These preservatives can be applied using different procedures. One of them is dipping, a method which is predominantly used in less industrialised countries. The most important parameter, that influences the quality of this treatment, is dipping time. Influence of various dipping times on copper retention, adsorption, penetration, colour of the specimens and copper fixation was examined. In this paper copper-ethanolamine solutions of two different concentrations were utilised (c_Cu=0.05% or 0.25%). The results showed that longer dipping treatments resulted in higher uptakes of preservative solution, better penetrations and lower leaching of copper-ethanolamine based wood preservatives from Norway spruce wood. After one week of dipping, samples retained on average 275 kg/m³ of preservative solution, copper active ingredients penetrated on average 3 mm into the specimens, and only 2.3% of copper was emitted from wood impregnated with aqueous solution of the higher concentration, when subjected to ENV 1250 leaching procedure.     

Development and Characterization of Biodegradable/Edible Wheat Protein Films

Biodegradable and edible films were prepared from three types of wheat flours: commercial bread, hard red winter, and soft white. Films were produced at two pH values (4 and 11) and tested for oxygen permeability as related to temperature. Films were also produced with a cross-linked agent and tested for tensile strengths. Oxygen permeability was 5.9 × 10^?20 to 18.5 × 10^?20 m³O₂ m m^?2 s^?1 Pa^?1 similar to values for commercial nylon. The oxygen permeability activation energy varied from 9.1 to 14.5 kcal mol^?1, depending on type of flour and pH did not affect oxygen permeability. Presence of the cross-linking agent increased the strength of films and elongation at break ranged from 490% to 640%, while tensile stress at break ranged from 25.8 × 10^?3 kg m^?2 to 44.1 × 10^?3 kg m^?2, lower than commercial nylon.