Spectral Range and Wood Surface Impacts on Equilibrium Moisture Content Estimation in Thermally Modified Beech Wood by FT-NIR Spectroscopy

Fourier transform near-infrared (FT-NIR) spectroscopy and partial least squares regression (PLS-R) were tested for the possibility of equilibrium moisture content (EMC) prediction in thermally modified beech wood (Fagus moesiaca C.). The samples were modified for 4h at temperatures of 170, 190 and 210 °C. After thermal modification, the samples were kept in a climatic chamber until EMC was reached. FT-NIR spectra (100 scans and 4 cm-1) were collected on the cross-section and radial surfaces at four points. PLS – R models were developed for four spectral regions: the first overtone, the second overtone, the third overtone and the combination band region. Applied thermal treatment caused a decrease of EMC by 42 % at 170 °C, by 53 % at 190 °C, and by 62 % at 210 °C. Principal component analysis (PCA) indicated that there is a difference both between treatments and between wood surfaces. The results of the spectra taken from the radial surface were, in all models, better than the spectra of the cross-section. Related to chemical changes, the first and second overtone region play an important role in the calibrations. The best prediction models for EMC of thermally modified beech wood were obtained from radial surface spectra in the first (Rp2=0.86, RPD=2.69) and second overtone region (Rp2=0.87, RPD=2.70). The obtain results could contribute to the development of predictive models in monitoring of EMC which could significantly improve the quality of industrial production of thermally modified wood.

INFLUENCE OF ELECTROMAGNETIC FIELD OF EXTREMELY LOW FREQUENCIES ON HYGROSCOPIC PROPERTIES OF WHEAT GRAIN MASS

The research results of the influence of electromagnetic field (EMF) of extremely low frequencies (ELF) on hygroscopic properties of Shestopalivka wheat variety of 2019 harvest have been given. Grain processing was performed on the experimental stand that consisted of the polymeric cylindrical container for grain, solenoid coil, generator of electromagnetic waves GZ-112/1 and a power amplifier of low frequency. The output signal of generator was set in the form of sine wave and controlled by oscillograph C1-78. The studies were performed at EMF frequencies of 10, 16, 24 and 30 Hz. Magnetic induction of grain treatment was constant and equaled 10 mTl. The duration of grain processing was 6 minutes.The equilibrium moisture content of wheat grain was determined by the tensometric method at temperatures t 9 °C and 23 °C and relative humidity φ 33…36 % and 82…82.5 %. The necessary conditions of air were created in desiccators with solutions of sulfuric acid placed in thermostats and refrigerators.It has been determined that the equilibrium moisture of wheat grain processed by EMFof ELF – is in the range of 12.17…20.56 %, and unprocessed grain – in the range of 12.62…21.03 %. Regardless of the frequency of EMF, equilibrium moisture content of the grain wheat processed by EMF varies according to the known laws – decreases with temperature increase and increases with increasing of air relative humidity. It has been shown that the impact of processing by EMF of ELF on the equilibrium moisture contentof wheat grain is manifested at different frequencies in different ways, which is likely due to the resonance phenomena. It has been established that the processing of grain by EMF with frequencies of 10...30 Hz practically has no effect on the equilibrium moisture content of grain at 23 °C and a relative humidity of 33...82.5 % which remains practically at the level of the unprocessed grain. It has been shown that the processing of grain by EMF with frequencies of 24 and 30 Hz under conditions of t = 9 °C and φ = 33 % leads to higher equilibrium moisture content compared to unprocessed wheat grain from 14.45 % to 16.85...16.95 %. Processing of grain with frequencies of 10 and 16 Hz under the same conditions, on the contrary – leads to a decrease in the level of equilibrium moisture content to 13.74…13.86 %. Empirical coefficients have been determined and the equation has been proposed that describes the dependence of equilibrium moisture content of not processed and processed wheat grain by EMF with frequency 10...30 Hz on temperature and relative humidity of the ambient air.

Variability in the mechanical properties of commercially available thermally modified hardwood lumber

Research indicates that users of thermally modified wood lack information regarding the improved performance and any variations that may exist for the “same” product when manufactured by different companies. The goal of this study was to evaluate the variability in mechanical properties of three thermally modified hardwoods and determine the variability between three different manufacturers. To determine the hardness, bending (modulus of elasticity and module of rupture) and shrinkage values, testing was conducted following ASTM standard D143. The samples were conditioned at 20 °C and a relative humidity of 65% until they reached an equilibrium moisture content before testing. Analysis of variance was used to determine the variability within and between the different processes used by each company. Seven out of 18 (39%) tests indicated that there were statistical differences regarding the mechanical performances of the wood samples. Yellow poplar had the least variation between companies (only difference in equilibrium moisture content, EMC) and red maple had the most (hardness, tangential shrinkage, and EMC). While the means for these properties were statistically different, the differences in application for hardness and EMC are slight. For example, the largest difference between processes in hardness was 83.6 kg, for tangential shrinkage, 0.45% and 1.37% for EMC. These differences are suggested to be inconsequential when compared to the values that exist between different species of untreated wood.

Calibration of Acoustic Emission Parameters in Relation to the Equilibrium Moisture Content Variations in a Pinus sylvestris Beam

Under constant temperature conditions, air relative humidity variations affect hygroscopic objects, such as wood, modifying their moisture content and provoking, at low values, damages and fractures. The parameters (amplitude, counts, and energy) derived from the acoustic emission non-destructive technique are calibrated with respect to equilibrium moisture content values using 14 samplings of Pinus sylvestris. The experimental procedure uses multi-technique approaches involving a universal testing machine, digital image correlation, and acoustic emissions, and notes that the three parameters of acoustic emission strictly depend on the equilibrium moisture content. For a better interpretation, a statistical approach is applied to model the equilibrium moisture content variations radially and longitudinally. Amplitude, counts, and energy are calibrated as a function of the equilibrium moisture content, indicating that all three parameters are necessary to have an integral vision of the conservation of a wooden material. Moreover, the shape of the macro-fractures that occur at the surface can be associated with the level of moisture or dryness of the sample. Finally, the proposed method can be used in situ because, through acoustic emission monitoring, it is possible to quantify the fingerprint of the state of conservation of a material.

Reliability Study of Equilibrium Moisture Content Methods for Sorption/Desorption Isotherms Determination of Autoclaved Aerated Concrete

Autoclaved aerated concrete (AAC) and its hygric parameters are a highly important issue in the field of building physics. There are several methods currently available to determine the equilibrium moisture content of building materials. Beside the conventional ones, new methods are constantly being introduced. This study explores the sorption/desorption properties of of three types of commercially produced AACs with three different bulk densities and demonstrates the application of the relevant methods available to characterize these parameters. The reliable characterization of the studied material was done through the conventional static approach, using the desiccator and an environmental chamber, and a new automated method of dynamic vapor sorption is implemented. The goal is to compare and identify the reliability of all methods used with respect to the efficiency of the data measurement process. Sound consistency between the results of the conventional methods and the experimental data obtained indicates the dynamic vapor sorption technique is highly reliable when measuring the equilibrium moisture content—particularly exemplified during the AAC sample testing. Therefore, the methodology developed in this study is expected to provide the reference for measuring the sorption/desorption isotherms of building materials with both static and automated techniques.

The interaction of water with archaeological and ethnographic birch bark and its effects on swelling, shrinkage and deformations

The aim of this study is to gain specific information on the water vapour interaction with archaeological and ethnographic birch bark. Water is involved in a number of curative and preventive conservation measurements e.g. when re-shaping or drying objects and when defining climate directives for long-term storage. We measured the sorption isotherm of archaeological, ethnographic and contemporary birch bark at different temperatures and analysed the moisture-induced size and shape changes (swelling, shrinkage, deformation) during humidification and drying. The analysis revealed that, compared to other organic materials like wood, the moisture uptake of outer birch bark is modest. This can be attributed to the cell structure and composition: outer birch bark is composed of closed cells made to a large extent of hydrophobic components (suberin, lignin). The equilibrium moisture content is higher if lenticels or inner bark are present. The extent of brittleness and delamination of the sample influences the sorption behaviour: the less brittle and delaminated archaeological birch bark is, the lower the equilibrium moisture content (EMC). Since the moisture uptake is modest, the related swelling of the outer bark is also modest, but anisotropic due to the cellular arrangement. Swelling is largest in the radial direction, smaller in longitudinal and negligible in tangential direction. Water vapour can plasticize birch bark and as birch bark becomes flexible, it bends towards the outside of the bark. This deformation takes place at high moisture contents and the adsorption process is slow. Based on these results recommendations on how best to perform treatments involving moisture and on relative humidity ranges for birch bark objects are provided.

Moisture content changes of beech and ash elements during two years in room conditions

The subject of this paper is the analysis of moisture content (MC) changes of beech and ash wood during two years in room conditions (heating during winter; no air conditioning during summer). The registered MC changes are primarily the result of changes in relative humidity of the air (measured by capacitive probes). The average relative humidity of the air in the interior is lower today than in the past, as also shown in this experiment (the average relative humidity of air during two years was 44%). The lowest wood MC was reached on very cold winter days when the heating was on even during the night - between 5% and 6%, and the highest one at the beginning of June: 10.4-10.9%. As expected, the wood did not reach equilibrium moisture content - during winter, MC is by about 1% higher, and in summer it is lower by up to 2.5% than the equilibrium. The recommendation that the sawn timber from which the interior products will be made should be dried at 7-8% MC was confirmed.

Effects of Post-Harvest Conditions on Sorption Isotherms of Soybeans

This study focuses on the modeling of sorption characteristics of three varieties of soybeans (Akras R2, Lono R2, and Podaga R2). Three pretreatments related to post-harvest conditions were tested on the soybean varieties: (1) freshly harvested soybeans, (2) soybeans subjected to three drying and wetting cycles, and (3) soybeans subjected to three freezing and thawing cycles. The adsorption and desorption experiments were conducted at 5°C, 10°C, 15°C, 20°C, 25°C, and 30°C using a dynamic equilibrium relative humidity (ERH) apparatus. Equilibrium moisture content (EMC) and the corresponding ERH were measured. The parameters calculated for the modified Halsey equation are applicable for storage temperatures above 10°C in the relative humidity (RH) ranges of 10% to 80% for desorption and 30% to 80% for adsorption. No significant differences were found in sorption isotherms among the soybean varieties. However, the soybean varieties responded differently to the different pretreatments (i.e., drying/wetting and freezing/thawing cycles). The adsorption isotherms of Akras and Lono soybeans showed significant differences at 10°C to 30°C when subjected to drying and wetting cycles, while Akras and Podaga soybeans showed significant differences in the same temperature range when subjected to freezing and thawing cycles. The effect of drying and wetting cycles on the desorption isotherms was found only for Akras soybeans at 10°C and 15°C below 63% and 71% RH, respectively, and for Lono soybeans at 25°C and 30°C above 69% RH for both temperatures. In general, the effect of both pretreatments on the sorption isotherms of soybeans was a reduction in EMC of up to 20%, when compared to fresh samples at selected storage temperatures. The findings of this study serve as a primary tool for developing a lookup table for safe storage guidelines for soybeans. Keywords: Equilibrium moisture content, Equilibrium relative humidity, Halsey equation, Oswin equation, Soybeans.