Volume 17 Issue 4

The recycling industry has developed rapidly in recent years. Paper, plastic, glass, and metals are the most recycled materials. In this study, composite boards were produced using recycled polyethylene (R-PE) mixed with used Tetra Pak® boxes (TPBs) and pine wood flour (PWF) as fillers. The ratios of TPB to wood flour used in study were 0%, 10%, 20%, 30%, and 40%. Six test groups of composites were prepared. For each group, four composite boards of dimensions 4 × 180 × 220 mm3 were produced. Some of the mechanical properties of the produced boards, such as the flexural strength, flexural modulus, tensile strength, tensile modulus, elongation at break, and Shore D hardness, were determined. The data obtained showed that the flexural modulus, tensile modulus, and density increased with the wood flour content. However, the flexural strength, tensile strength, and elongation at break decreased as the wood flour content was increased. As a result, it can be said that TPBs could be used as a filler instead of wood flour in the production of wood-plastic composites.

Condensed tannins were quantified in the barks of selected tree species, and the antibacterial activity of these substances against clinical and subclinical isolates of bovine mastitis were evaluated. Tree barks from Mimosa tenuiflora, Mimosa caesalpiniifolia, Anacardium occidentale, and Stryphnodendron adstringens were used, as well as commercial tannin from Acacia mearnsii. The tannins were extracted using a mixture of ethyl alcohol and acetone. The moisture content (MC), Stiasny index (SI), total solids content (TSC), and condensed tannins (CT) were measured. The evaluation of antimicrobial activity was determined by applying the disk diffusion test. The species that showed the highest CT were M. tenuiflora and A. occidentale, with 37.3% and 37.3%, respectively. The highest SI were obtained by the species A. occidentale and M. caesalpiniifolia, with values above 90%. The bacterium with the lowest resistance to the use of tannins was Streptococcus uberis. A. mearnsii was the only one capable of inhibiting the growth of Escherichia coli, with a mean inhibition halo of 9 mm. All species under study showed high values of condensed tannins in their barks. In addition to showing good performance as antimicrobial agents, these tannins indicated potential applications in the development of natural medicines for the treatment of bovine mastitis.

Wood is a complex, natural structure and an essential source of nutrition, construction and building materials, energy, etc. Because of its microscopic structure, it is difficult to model its composition. In this study, the bio-mimicry of annual rings of the wood was evaluated by modeling and printing four different models with different ring diameters. The CATIA v5 software was used for 3D modeling. The designed models were additively manufactured using a 3D printer via the fused deposition of the acrylonitrile butadiene styrene (ABS) filament. The infill density and type, shell, layer height, and printing speed were evaluated for their influence on the structure of the ring. According to the results of preliminary biomimetic experimental, none of the models were exactly printed using the FDM method and ABS filament. Furthermore, the printing parameters did not significantly improve ring structure formation. Only the earlywood section of Model 4 could be moderately printed. Therefore, using these tools with printing parameters and materials was not found to be suitable for bio-mimicry of tree rings even if the size of the rings was multiplied by ten. In future work, the same models will be printed using different methods and tools to evaluate the printing ability or differences.

Lignin (SCEL) was separated from steam-exploded eucalyptus wood fibers using a supercritical carbon dioxide (scCO2)–ethanol/water composite medium, which was compared with traditional industrial alkaline extraction of lignin (AL) and high-temperature ethanol extraction of lignin (EL). All three kinds of lignin were spray-dried to form microparticles. The obtained SCEL, AL, and EL particles were mixed with poly(vinyl alcohol) (PVOH) to prepare a composite film. Compared with the pure PVOH film, the transmittance of the composite film to ultraviolet light was reduced from more than 70% to less than 20%, and the tensile strengths of the SCEL/PVOH, AL/PVOH, and EL/PVOH films were increased by 79.2%, 39.1%, and 66.0%, respectively. The water contact angle was increased from 35.5° to 95.3°, 59.5°, and 66.7°, respectively. In terms of performance improvement, SCEL had a better effect. The SCEL particle size was small and uniform, and SCEL contained more S-type structural units and β-O-4 bonds, which is conducive to its uniform dispersion in the PVOH matrix and increases the contact area between lignin and ultraviolet light, thereby improving its anti-ultraviolet performance. The hydrophilic groups in lignin form a large number of hydrogen bonds with PVOH, which promotes the combination of lignin and PVOH, and at the same time exposes a large number of hydrophobic groups of lignin, which improves the mechanical properties and the hydrophobicity of the film.

Waste newspapers (WNPs), composed of mostly wood fibers and small amounts of inorganic fillers and printing ink, are a low-cost, abundant, and readily available form of household waste. Urea formaldehyde (UF) resin is used routinely to produce wood-based panel boards even though it releases harmful formaldehyde. The best way of resolving this issue is to use formaldehyde-free adhesives from renewable resources. Kraft lignin, a readily available, low-cost, and renewable waste product from the pulping industry, is used mainly as a fuel. Kraft lignin has good bonding ability to wood-based panel boards and improves water resistance. In this research, fiberboards were produced using a dry-processing method from recycled WNPs and bonded with kraft lignin instead of UF. The physical and mechanical properties of the produced fiberboards were evaluated. The results showed that the hot press temperature and kraft lignin content remarkably influenced the physical and mechanical properties of the fiberboards. As the hot press temperature and kraft lignin content increased, the overall performance of the fiberboards improved accordingly. The results indicate that WNPs could be a potential sustainable resource for fiberboards production.

This study was conducted to determine the lignin substructures, hydroxyl (phenolic + aliphatic) contents, and carboxyl contents in kraft lignin (KL) prepared from mixed hardwoods by using 2D Heteronuclear Multiple Quantum Coherence Nuclear Magnetic Resonance (HMQC NMR) and 31P NMR techniques. Based on 2D HMQC NMR analysis of KL, stilbene and vanillin substructures were present in the aromatic region, while trace amounts of β-O-4 and β-β moieties were detected in the oxygenated aliphatic region. The total hydroxyl content calculated from 31P NMR was 5.24 mmol/g KL. The aliphatic hydroxyl content was 1.04 mmol/g KL, and phenolic hydroxyl content was 4.20 mmol/g KL. Of the phenolic hydroxyl groups, the contribution of syringyl (S) and guaiacyl (G) was 1.02 and 0.97 mmol/g KL, respectively. The S/G molar ratio of KL calculated from 31P NMR was 1.05. The carboxyl content was 0.44 mmol/g KL.

Tomography is a technique increasingly used in tree inspections. This technique can be performed in two stages: field testing and postimage processing. To feed the tomographic image construction software, it is necessary to adopt a measurement grid composed of points positioned on the perimeter of the stem. The images are generated through spatial interpolation algorithms. From a theoretical point of view, more measurement points taken in the perimeter of the stem result in better interpolation results. However, an increase in the number of mesh points causes a substantial increase in field work and image processing time. The general objective of this study was to verify the influence of the number of measurement points of the diffraction mesh on the ultrasound tomography results. For this purpose, ten simulated discs were used, all 500 mm in diameter and with different defects in terms of size, position, and geometry. In each of the discs, diffraction grids were simulated with 6, 8, 10, 12, and 14 measurement points in the contour. The results showed that a favorable combination of accuracy and a minimization of effort can be achieved with diffraction mesh with number of measurement points calculated as five times the perimeter of the trunk in meters.

The aim of the work was to define a suitable dimensional solution for a single-occupancy bed from wood composites for the adult bariatric population of Slovakia. Current bed dimensions are designed for the adult population for standard human dimensions and weight up to 150 kg. Based on the long-term observation of the development of anthropometric dimensions of the population (secular trend), the height of 95% of the adult male population was defined. Based on the analysis of the bariatric population of Slovakia, regardless of gender, the values of weight, waistline and hipline, and seat width were defined in the years 2020 to 2022. Based on the results, the weight of the bariatric population can be up to 250 kg. New bed dimensions for bariatric respondents were proposed, including bed length according to room dimensions from 220 cm to 240 cm, bed width of 141 cm, and bed height of 55 cm. By adjusting the dimensions of the beds for bariatric respondents, they will be able to move comfortably during rest and sleep. This can prevent many health problems.

Wood when exposed to accelerated weathering conditions is deteriorated as a result of factors such as UV rays, temperature, and relative humidity changes. The surface roughness of wood also undergoes substantial changes. In this study, the effect of accelerated weathering conditions on surface roughness changes on Scots pine (Pinus sylvestris L.) and poplar (Populus x euroamericana) wood surfaces were investigated using the Taguchi method. The parameters most affecting the surface roughness were radial direction, 0.5 W/m2 UV, 4 h conditioning time, and 45 min water for Scots pine, and tangential direction, 0.5 W/m2 UV, 2 h conditioning, and 15 min water for poplar wood. The variables that most affected the surface roughness were conditioning with 38% in Scots pine wood and wavelength with 31% in poplar wood.

Three kinds of pore-forming agents (corn flour, starch, and biochar) were selected to prepare dolomite-based porous ceramic catalyst carriers with good mechanical properties. Pore-forming agents occupy space within preformed agglomerates, such that after the pyrolysis and sintering have been completed there are spaces within the resulting ceramic material. Porous ceramic samples prepared with biochar exhibited high apparent porosity and water absorption. By contrast, the apparent porosity of the porous ceramic samples prepared with starch as the pore-forming agent was low. When the ratio of the dolomite to quartz sand in the ceramic aggregate was changed from 4:6 to 3:7, the change of the apparent porosity of the porous ceramic samples made with starch as a pore-forming agent was very small, with high bulk density and compressive strength. Compared with corn flour and biochar, starch was less suitable as a pore-forming agent for porous ceramics. The apparent porosity and water absorption of the porous ceramics prepared with biochar as a pore-forming agent decreased slightly. But its bulk density and thermal conductivity were increased. This is mainly attributable to the fact that biochar is lighter, but it performs well in terms of mechanical strength and thermal conductivity.