Research Articles

Wood from the fast-growing poplar cultivar “Hybrid 275” (P. maximowiczii x trichocarpa) was defibrated under industrial conditions, and the resulting fibers were subjected to impregnation modification with 5% or 10% 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU). The modified fibers were used to produce 3-mm thick high density fiberboards (HDF). The mechanical testing revealed that DMDHEU provided an increase in modulus of elasticity (MOE) and a decrease in modulus of rupture (MOR); however, all panels met the requirements of the European Standard EN 310 (1993). Increases of 1.5-fold and 2.5-fold in internal bonding (IB) compared to the unmodified reference panels were observed. The modification resulted in reduced HDF interactions with water, manifested by decreased water absorption, thickness swelling, and reduced water wetting. The modification also provided the panels with an improved resistance to moulds.

Different types of sanders are used in every furniture factory and carpentry plant. The wood dust generated during sanding is considered to be one of the main health and safety hazards. Based on many studies, the whole inhaled fraction of particles less than 100 μm is harmful to health. Thus, it is important to know the specific particle size fractions of wood dust. This study compared the granulometric compositions of sanding wood dusts of selected wood species (beech and oak) and determined the statistical significance of individual factors (type of sander, wood species, grain size of sander, sanding direction) that affect the percentage of fractions ≤ 0.08 mm. The results confirmed that the use of narrow band and handheld (belt and disc) sanders caused high percentages of fractions ≤ 0.08 mm, above 90% in all cases. In these types of sanders, the working part of the sander is not completely covered, and the operator is in direct contact with the machine. Despite the use of a suction device, a certain amount of dust remains suspended in the air, or it settles on surfaces.  In both cases, this dust poses a health and safety hazard.

This study focused on the use of evapotranspiration as a means of drying wood. This principle is based on the fact that tree species with outstanding sprouting capacities are able to leaf after being felled and are physiologically active until they have enough water. The course of wood drying (the stems and branches) was examined in relation to their subsequent foliage creation and ongoing evapotranspiration, and how those factors related to other factors (temperature and precipitation). As for stems, the drying process proved to be more effective in samples with buds and less effective in samples without buds. As for branches, the samples with buds had a slightly higher weight in the long-term average, but during the sprouting season their drying was more efficient. These findings may help achieve more efficient handling of the timber from fast-growing species in relation to their processing and storage.

The material basis of nutshells was explored in this study for Camellia oleifera Abel, Castanea mollissima Blume, and Carya cathayensis Sarg., The authors measured the moisture content, pH, electronic conductivity (EC), seed germination index (GI), and tannin content of the fresh shells of these three species. The contents of cellulose, hemicellulose, lignin, organic extracts, ash, saponin, cellulose crystallinity, organic carbon, and mineral elements of the dried shells was also measured. The results showed that the total mass fractions of cellulose, hemicellulose, and lignin in the shells of the three species were all above 80% of dry weight; the content of organic matter was higher than 66%, and the pH values were in the range of 5.5 to 8.5. The shells of the three species are good raw materials for the growth of plants and edible fungi. There were some shortcomings if used as fertilizers or substrates. However, the C/N and C/P ratios were high, the EC values were low, and the GI was < 100%. Additionally, the shells all contained tannin, saponin, and alkaloids, which were not conducive to the growth of plants and mycelia of edible fungi. Therefore, they can be used as culture media only after being processed.

To explore the distribution of paper strengthening agent polyamideamine epichlorohydrin (PAE)/sodium alginate (SA) binary system in handsheets, SA was labeled by fluorescein isothiocyanate (FITC) to trace the system in paper. 1,6-diaminohexane was used to link SA and FITC to prepare fluorescein isothiocyanate sodium alginate (F-SA), and the optimal synthesis conditions of SA and 1,6-diaminohexane were evaluated. F-SA was identified by ultraviolet (UV) spectral scanning, Fourier transform infrared spectroscopy (FTIR), and fluorescence microscope. The PAE/F-SA binary system in the paper sheet was detected with a fluorescence microscope. The results indicated that FITC could successfully label SA marked as F-SA. The fluorescence substitution degree was 0.89%. Compared with the PAE/SA binary system, the PAE/F-SA binary system produced significant fluorescence in the paper, which indicated that the PAE/SA binary system was evenly distributed and formed a network structure in the handsheets. Furthermore, this method of fluorescence labeling could be employed in papermaking.

Pinus massoniana material was processed on a shaper in which a quartz three-component dynamometer and forward-looking infrared (FLIR) system were used to measure the cutting forces and cutting zone temperature, respectively. In addition, a high-speed camera and the FLIR systems were used to capture the chip formation process. Cutting forces and cutting zone temperature were measured under the cutting conditions of three different rake angles (25°, 40°, and 50°) and four different cutting depths (0.1 mm, 0.2 mm, 0.3 mm, and 0.5 mm), while feed speed was kept constant. Analysis of the experimental data and chip formation process showed that the cutting forces and cutting zone temperature of pine material were both decreased by increases of rake angle and increased by increases of cutting depth. Cutting forces were decreased under the cutting conditions of 0.3 mm cutting depth and rake angles of 40° and 50° due to the cleavage failure parallel to pine grain. The cutting temperature was not decreased under that cutting condition. The microcosmic characteristics of surface damage were mainly fiber burrs and fiber traces.

Deep eutectic solvents play an important role in the clean production of chemicals and the fractionation of renewable sources. When dissolving lignin or cellulose at elevated temperatures, the thermal stability of deep eutectic solvents is of great importance. However, studies concerning the long-term isothermal stability of deep eutectic solvents are scarce. In this study, the thermal stability of deep eutectic solvents, namely, choline chloride with oxalic acid dihydrate, glycerol, glycolic, malic acid, and citric acid monohydrate were investigated using thermogravimetric analysis (TGA). The isothermal decomposition experiments were conducted at a constant temperature (60, 80, 100, and 120 °C) for 10 h. These long-term isothermal thermogravimetric studies of the deep eutectic solvents showed a non-linear weight loss as a function of time at each temperature. According to these studies it is recommended to perform fractionation or dissolution of biomass below 80 °C.

This study characterized the structure of food packages, determined the amount of toxic metals that pass through the package (due to the package’s condition and contact with food), and examined the appropriateness of current food legislation. The food packages were examined for weight, ash content, and optical properties under two different light sources. The toxic metal quantities of the packages were analyzed with the use of an inductively coupled plasma optical emission spectrometry (ICP-OES ). In all packages, Pb migrated into food and was found at levels that exceeded limit values. Although the amounts of Hg within the material structure were above limits in most packages, it did not migrate from the packages. Although the amount of Cd in structural packaging did not exceed the limit values, most of the migration-related values were high. The Zn concentration in packaging was substantially higher than the amount due to migration. Structural Cu values were mostly below the limit values, except in corrugated boards. Cr amounts in both packaging structure and migration were below the limit values. In all packaging, there were minimum amounts of Ni among paperboard samples and maximum amounts among corrugated boards. Al values were high among structural paper packages, as well as in migration values in paperboard packaging.

In Laos and neighboring countries, opportunities exist for the production of engineered wood products such as plywood and laminated veneer lumber to supply the rapid growth of construction, furnishing, and joinery activities. The objective of the present study was to assess the potential of peeling fast-growing high-yielding pulpwood from managed eucalypt stands in Laos for veneered products. Eucalyptus pellita, Eucalyptus camaldulensis, and eucalypt clone K7 (E. camaldulensis × E. deglupta) stands were characterized based on veneer quality and recovery. The influence of log position, log geometry, and other log traits during recovery were also investigated. The selected taxa achieved green veneer recoveries that ranged between 57% and 67%. End splitting and branch-related defects were the most important grade-limiting defects that restricted veneer sheet quality to a lower grade of most sheets. However, simple timely silvicultural decisions, such as pruning, could significantly help improve the quality of veneer obtained. The obtained results could be used in the formulation of recommendations to adopt better management practices in Laos to improve the value of plantation-grown wood.

Unfinished, polyvinyl chloride-faced (PVC-faced), and melamine-finished particleboards were examined to determine the effects of VOCs released from these particleboards on indoor air quality. A climate chamber and GC/MS was used to analyze the changes in the concentration of volatile organic compounds (VOCs) from these particleboards over a single cycle of 28 days. The main pollutants from the unfinished particleboard were esters, aromatic hydrocarbons, and aldehydes ketones; the pollutants released from the PVC-faced and melamine-finished particleboards were esters, and aldehydes and ketones. The VOCs from the PVC-faced particleboard had the lowest impact on indoor air quality. When the released VOCs from PVC-faced particleboard reached their stable floor-level values, the air quality was grade I, which is suitable for living. When unfinished and melamine-finished particleboards were used individually indoors, the air quality was grade IV and V. After the released VOCs reached their stable floor-level values, the indoor air quality was grade I or II, which met the standards for living conditions. Under the premise of ensuring that the indoor air was not polluted, the maximum loading rates of the unfinished, PVC-faced, and melamine-finished particleboards were 2.0 m²/m³, 3.8 m²/m³, and 3.8 m²/m³, respectively.