Dynamic water vapor sorption experiments were carried out using beech wood dust (from untreated and thermally modified wood) of two-particle sizes, (< 25 and 80–250 µm), obtained from abrasive ...sanding. Sorption isotherms were parameterized with the GAB and GDW models. Dust from thermally modified wood had significantly lower equilibrium moisture content compared to dust from untreated material, due to the reduction in primary sorption sites in treated material. The observed changes were quantified by the coefficients of the GAB and GDW models. Thermal modification and size of wood dust particles had no influence on binding energy of water molecules being linked to the secondary sorption sites. Water diffusivity decreased significantly with increasing moisture content, but only for monolayer sorption. For higher moisture content values, water diffusivity was practically independent of moisture content. These results were found for untreated and thermally modified material as well as for both dust size fractions. The influence of thermal modification on water diffusivity was unclear, which is attributed to the diffusion model, which represents dust particles as spheres and assumes instant hygroscopic equilibrium. Overall, this study indicates that the effectiveness of filtration processes likely depends strongly on sorption and diffusion properties of wood dust only at low moisture contents within the hygroscopic range.
Swelling and shrinkage anisotropy affect the susceptibility to an assembly of wooden elements by changing designed clearances or interference fits. This work described the new method to measure ...mounting holes' moisture-induced shape instability and its verification using three sets of twin samples made of Scots pinewood. Each set of samples contained a pair with different grain patterns. All samples were conditioned under reference conditions (relative air humidity-RH = 60% and temperature 20 °C), and their moisture content (MC) reached equilibrium (10.7 ± 0.1%). On the side of each sample, the seven mounting holes of 12 mm in diameter were drilled. Immediately after drilling, Set 1 was used to measure the effective hole diameter with 15 cylindrical plug-gauges with diameters of 0.05 mm step, while Set 2 and Set 3 were separately re-seasoned by six months in two extreme conditions. Set 2 was conditioned with air at 85% RH (reached an equilibrium MC of 16.6 ± 0.5%), while Set 3 was exposed to air at 35% RH (reached an equilibrium MC of 7.6 ± 0.1%). Results of the plug gauge tests highlighted that holes in the samples subjected to swelling (Set 2) increased an effective diameter in the range of 12.2-12.3 mm (1.7-2.5%), while samples subjected to shrinking (Set 3) reduced the effective diameter to 11.9-11.95 mm (0.8-0.4%). To accurately reproduce the complex shape of the deformation, gypsum casts of holes were made. The 3D optical scanning method was used to read the gypsum casts' shape and dimensions. The 3D surface map of deviations analysis provided more detailed information than the plug-gauge test results. Both the shrinking and swelling of the samples changed the shapes and sizes of the holes, but shrinking reduced the effective diameter of the hole more than swelling increased it. The moisture-induced changes in the shape of holes are complex: the holes ovalized with a different range, depending on the wood grain pattern and hole depth, and were slightly extended in diameter at the bottom. Our study provides a new way to measure 3D hole initial shape changes in wooden elements during desorption and absorption.
Mill. is a favourite tree used in urban spaces. For this reason, it is important to know its sensitivity to environmental stress, which is particularly burdensome for vegetation in urban spaces. The ...aim of the study was to investigate the properties necessary to control the growth of these trees and their subsequent use, i.e., chemical properties (percentage contents of cellulose, holocellulose, lignin, pentosans and substances soluble in NaOH and EtOH) as well as the chemical elements (K, Na, Mg, Ca and Fe, Zn, Cu, Pb, Cd, B, Ni, Cr, Al, As and Hg) and selected hygroscopic properties (hysteresis and sorption isotherms). Trees of
Mill. growing in environments exposed to environmental stress of varying severity were examined. Regardless of the growth conditions, in terms of its chemical composition, bark differs significantly from wood, showing twice the contents of soluble substances in NaOH and lignin and half the content of polysaccharides. Growth conditions clearly affect the range of selected chemical components in bark, e.g., substances soluble in ethanol, cellulose, or lignin. The main inorganic elements in bark and wood are Na, K, Ca, Mg and Zn. In bark, a relationship was found between the content of most chemical elements and differing environmental growth conditions. It was shown that environmental stress influenced the hygroscopic properties of wood and bark, which are a consequence of the percentage of chemical components.
Over the last decade, there has been increased interest in applying biomass as a raw material for producing biofuels used for thermochemical conversions. Extensive use of biomass could lead to ...controversial competition for arable land, water, and food; therefore, only waste materials and agricultural by-products and residues should be used to produce biofuels. One suitable by-product of agricultural production is crop residue from the harvest of maize for grain (corn stover). The harvest residues of corn stover consist of four fractions, i.e., husks, leaves, cobs, and stalks, which are structurally and morphologically distinct. The aim of the study was to determine the effect of selected maize cultivars with distinct FAO (Food and Agriculture Organization of the United Nations) earliness classifications on the chemical and energetic properties of their corn cob cores. We determined the chemical properties based on elemental analysis, and the energy properties based on the heat of combustion and calorific values. The content of ash and volatile compounds in the corn cobs were also determined. The results indicated that the heat of combustion of fresh and seasoned corn cob cores ranged from 7.62-10.79 MJ/kg and 16.19-16.53 MJ/kg, respectively. The heat of combustion and calorific value of corn cob cores in the fresh state differed significantly and were strongly correlated with maize cultivars with distinct FAO earliness.
European ash (
L.) is one of the species commonly used for wood thermal modification that improves its performance. The presented research aimed to investigate a moisture-dependent strength ...anisotropy of thermally-modified European ash in compression. Wood samples were modified at 180 °C and 200 °C. Their mechanical parameters were determined in the principal anatomical directions under dry (moisture content of 3%) and wet (moisture content above fibre saturation point) conditions. Effect of heat treatment temperature and moisture content on the ash wood mechanical parameters concerning each anatomical direction were determined. The results show that thermal treatment kept the intrinsic anisotropy of wood mechanical properties. It decreased wood hygroscopicity, which resulted in improved strength and elasticity measured for wet wood when compared to untreated and treated samples. Higher treatment temperature (200 °C) increased wood elasticity in compression in all the anatomical directions despite wood moisture content during the measurements. Multivariate analysis revealed that the modification temperature significantly affected the modulus of elasticity perpendicular to the grain, while in the case of compression strength, the statistically significant effect was observed only parallel to the grain. The results obtained can be useful from an industrial perspective and can serve as part of a database for further modelling purposes.
Low-intensity drying is widely believed to protect waterlogged archeological wood against the adverse effects of dimensional alteration and cracking. However, slow drying generates substantial costs ...for the conservation process. This study compares the effects on conservation of highly-degraded sapwood (SW) and slightly-degraded heartwood (HW) from waterlogged archeological Scots pine wood treated with polyethylene glycol either as a mixture of polyethylene glycol (PEG) 400/4000 or PEG 2000 solution and air-dried using different approaches. The reference air-drying approach, using gradually decreasing air relative humidity (RH), i.e., 96, 86, 75, 66, and finally 44% (multi-stage schedule), was compared to an alternative approach, using constant RH of 44% (single-stage schedule). The Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the decomposition of hydrophilic chemical wood components and revealed differences in the degree of degradation of waterlogged SW and HW. The drying time of PEG-treated waterlogged wood air-dried using a one-stage schedule was shorter compared to the drying time using multi-stage drying. Multivariate analysis (ANOVA) revealed that the drying schedule used after impregnation of waterlogged wood with PEG can have a beneficial effect on wood hygroscopicity and dimensional stability. The drying schedule significantly affected the equilibrium moisture content (EMC) of SW and HW and reduced tangential (ST) shrinkage of SW. These results show the positive effect of the single-stage alternative drying approach on the dimensional stability of highly-degraded Scots pine SW impregnated with PEG 2000. In the case of slightly-degraded HW, the drying approach did not affect wood preservation. These results can be useful for the conservation of highly-degraded waterlogged Scots pine wood.
The research aimed to obtain empirical data for modeling the initial desorption in reaction wood from the cross-section of the green beech (Fagus sylvatica L.) log. Firstly, we analyzed the chemical ...composition, macro and microscopic structure of tension and opposite wood tissue. Then, the Equilibrium Moisture Content (EMC) was measured by the Dynamic Vapor Sorption method during the initial desorption. The used air parameters were specific for the mild drying schedule of green beech timber (t = 20, 35, and 50 °C, Relative Humidity (RH) ranging from 95 to 0 %). Relationships between the EMC of reaction wood and drying parameters were modeled using the Response Surface Method (RSM). The tests revealed: different hygroscopic properties of tension and opposite wood, the dependence of EMC value on temperature, and differences between EMC values for initial (first) and second desorption. Moreover, it was confirmed that, during initial desorption, the EMCs of reaction wood are significantly higher than reference EMC data. The differences in the EMC value are up to 0.14 kg/kg (for air with RH above 90 %). The presented polynomial model of the initial desorption of reaction beech wood can improve drying schedules for beech sawn timber with a high amount of reaction tissue.
Cilj je ovog istraživanja modeliranje inicijalne desorpcije poprečnog presjeka reakcijskog drva bukve (Fagus sylvatica L.) na temelju empirijskih podatka. Najprije je istražen kemijski sastav drva te je analizirana makroskopska i mikroskopska struktura reakcijskoga i opozitnog drva. Zatim je metodom dinamičke sorpcije pare izmjeren ravnotežni sadržaj vode tijekom inicijalne desorpcije. Drvo je podvrgnuto blagom režimu sušenja (t = 20, 35 i 50 °C, te relativnoj vlažnosti zraka u rasponu od 95 do 0 %). Odnosi između ravnotežnog sadržaja vode reakcijskog drva i parametara sušenja modelirani su metodom odzivne površine. Ispitivanjem su dobivena različita higroskopska svojstva reakcijskoga i normalnog drva, ovisnost ravnotežnog sadržaja vode o temperaturi sušenja te razlike između vrijednosti ravnotežnog sadržaja vode pri inicijalnoj (prvoj) i drugoj desorpciji. Također je potvrđeno da je ravnotežni sadržaj vode reakcijskog drva tijekom inicijalne desorpcije znatno veći od referentnih vrijednosti ravnotežnog sadržaja vode normalnog drva. Razlike u vrijednostima ravnotežnog sadržaja vode kreću se do 0,14 kg/kg (pri relativnoj vlažnosti zraka većoj od 90 %). Prikazani polinomski model inicijalne desorpcije reakcijskog drva bukve može poslužiti za poboljšanje režima sušenja bukove piljene građe s velikim udjelom reakcijskog drva.Ključne riječi
Thermal modification of spruce wood (Picea abies L.) was conducted at three different temperatures (160, 200, and 240 °C) and treatment times (1, 3, and 5 h). The cyclic sorption experiments were ...performed for relative humidity changes of 30 to 85%. The equilibrium moisture content of the thermally modified wood was reduced up to 50% after treatment at 240 °C for 5 h. The sorption isotherms were described with the Guggenheim, Anderson, and De Boer (GAB) model. Cyclic sorption increased the monolayer capacity. Thus, the monolayer sorption was increased, while the multilayer sorption was limited. The dependence of the mass loss, hysteresis loop, and the maximum difference of equilibrium moisture content on the modification temperature and duration was modeled by response surface methodology. There was a very strong correlation between the modification temperature and mass loss, while the relationship between treatment time and mass loss was insignificant. The correlations between the modification parameters and the descriptors of sorption hysteresis were stronger after cyclic sorption. The sorption hysteresis decreased after cyclic sorption. This result was mainly caused by the increase of the monomolecular sorption for the adsorption processes.
The aim of the research was to determine the influence of chitosan type and propolis extract concentration on biological and physicochemical properties of chitosan-propolis films in terms of their ...applicability in food packaging. The films were prepared using three types of chitosan: from crab shells, medium and high molecular weight and propolis concentration in the range of 0.75–5.0%. The prepared polysaccharide films were tested for antimicrobial properties, oxygen transmission rate (OTR) and water vapor transmission rate (WVTR). Moreover, sorption tests and structural analysis were carried out. Microbiological tests indicated the best antimicrobial activity for the film consisting of high molecular weight chitosan and 5.0% propolis extract. Both the type of chitosan and propolis concentration affected transmission parameters—OTR and WVTR. The best barrier properties were recorded for the film composed of high molecular weight chitosan and 5.0% propolis extract. The results of sorption experiments showed a slight influence of chitosan type and a significant effect of propolis extract concentration on equilibrium moisture content of tested films. Moreover, propolis extract concentration affected monolayer water capacity (Mm) estimated using the Guggenheim, Anderson and de Boer (GAB) sorption model. The obtained results indicate that chitosan films with an addition of propolis extract are promising materials for food packaging applications, including food containing probiotic microorganisms.
The study's objective was to assess the particle-size distribution and formulate an empirical model for the content of the finest dust created during the sanding of unmodified and thermally modified ...pine wood. The experimental design included unmodified and two options of thermally modified pine (Pinus sylvestris L.) wood samples, four feed speeds (3; 6; 9; 12 m·min
−1
), and three grit sizes of sanding belts (P60; P80; P100). The wood dust samples underwent sieve analysis to determine the particle-size distribution and laser analysis to determine the content of the finest particles. The sanding of thermally modified wood produced a higher amount of fine dust compared to unmodified wood. The content of fine dust increased with decreasing feed speed, while larger grit sizes resulted in increased production of fine dust. The average mass share of dust < 2.5, < 4, and < 10 µm was significantly lower when sanding the unmodified wood than thermally modified wood. The influence of feed speed, grit size, and material type on dust creation suggests that thermal modification is a factor in increasing the content of the potentially harmful finest particles (respirable fraction). The presented empirical model can help minimize health risks during the sanding of thermally modified pine wood by adjusting the sanding parameters.
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