Research Articles

Knowledge of the force required to overcome deformation at the proportionality limit, maximum limit, and their ratio, as well as knowledge of the effect of selected factors on the listed characteristics in bending stress, have both scientific and practical significance. They form a foundation for designing tools for bending and determine the stress that products and their parts can be exposed to during use. This study analyzes the effect of selected factors on the force at the proportionality limit (FE), the force at the maximum limit (FP), and the ratio of these two characteristics (FE/FP). This study examined the effect of the wood species (WS) (Fagus sylvatica L. and Populus tremula L.), material thickness (MT) (4 mm, 6 mm, 10 mm, and 18 mm), degree of densification (DOD) (0%, 10%, and 20%), and the number of cycles (NOC) (0 or 10,000), as well as their combined interaction, on the monitored characteristics. The results contribute to the advancement of knowledge necessary for the study and development of new materials with specific properties for their intended use. The results can improve the innovative potential of wood processing companies and increase their performance and competitiveness in the market.

Sudan has rich sources of lignocellulose materials from agricultural waste that have potential to be used as a papermaking furnish following adequate chemical compositions, elemental analysis, fibre dimensions, and morphology of millet stalks and date palm leaves. Paper sheet properties from the various pulps made were investigated, and it was found that there was no difference in the polysaccharide (cellulose and hemicelluloses) content between millet stalks and date palm leaves, although millet stalks had a high lignin content of 18.20% relative to date palm leaves’ content of 15.34%. Moreover, millet stalks showed a high pulp yield (42.04%) with a viscosity of 665 mL/g compared to that (34.43%, 551 mL/g) and (38.50% and 534 mL/g) of date palm leaves and the blend, respectively. Papers produced from date palm leaves and millet stalk blends showed better physical properties compared to that of pure millet stalks and date palm leaves. The Scanning Electron Microscopy (SEM) analysis showed that fibres in the blend were more closely packed than that of the pure millet stalks and date palm leaves fibers. Based on their physical and chemical composition properties, millet stalks and date palm leaves have a high potential as a furnish for pulp and papermaking.

Molds in wet and warm environments often attack surfaces of products made from beech and other less or moderately durable woods. This paper presents the effects of the physical modification of beech wood with a CO2 laser having a constant power output of 45 W, using eight radiation doses from 7.8 to 75 J/cm2. Variations in laser activations created a scale of color changes in surfaces of beech wood determined in the CIE L*a*b* system, ranging from an apparently unaffected to totally dark due to carbonization effects. The surfaces of beech samples modified by laser were subsequently infected with the molds Aspergillus niger and Penicillium brevicompactum, and their growth on the top surfaces of beech samples was evaluated according to the standard STN 49 0604 (1980). The modified surfaces of beech wood exposed to higher CO2 laser powerful effects (i.e., radiation doses 25 J/cm2 and more) obtained evidently higher resistance to Aspergillus niger, but their resistance to Penicillium brevicompactum changed only minimally.

Mold invasion by Trichoderma harzianum T6776 over the surface of wood-plastic composites (WPCs) made from Juniperus procera wood-branch and polypropylene with a melt-blending technique was examined using scanning electron microscopy (SEM) and electron dispersive X-ray spectroscopy (EDX). Before the addition of coupling agent, the WPC samples were made from untreated and pretreated wood-branch particles of J. procera with either cold or hot water and then mixed with polypropylene to produce panels. The surfaces of WPC samples were inoculated by a mold suspension of T. harzianum. SEM-EDX measurements of WPCs made from J. procera particles showed little or no growth of T. harzianum, irrespective of treatment with cold or hot water. The results suggest that WPCs made from the particles of J. procera wood-branch pretreated with either cold or hot water could be useable in wet conditions. In addition, using of J. procera as durable wood for manufacturing of WPCs had good effects on the prevention of the mold infestation over the surfaces of the produced panels.

This study deals with calculating and comparing the bending moments of two types of corner joints for commercially produced wooden sashes. The triple tenon and mortise joint was compared to a dowel joint on the sash of a window profile IV 92, made of spruce glued laminated timber. On the testing machine, the maximum force in the angular plane of a window sash under compression or tension mode was applied, and the measured values were converted to the bending moments. A significant difference between the bending moments for the mortise and tenon joint, and dowel joint were determined. The dowel joints achieved 167 Nm in a tensile test and 168 Nm in a compression test, while the mortise and tenon joint achieved 344 Nm in a tensile test and 325 Nm in a compression test. However, a significant difference was not revealed between the compression and tension tests for both types of joints. The differences for both types of joints were explained via the different sizes of the bonded surfaces, which was higher for the tested triple tenon and mortise joint by 29%.

The degradation of lignocellulosic materials requires the synergy of multiple enzymes. Synergistic fermentation would be an alternative to a complete enzyme system and consequentially enhance enzymatic production. The present study used cellulolytic fungus of Penicillium decumbens, Aspergillus niger C112, and Trichoderma reesei RutC-30 as the starting strains, to screen for the best combination and proportion of synergistic fermentation. The experiments of different combinations and inoculum ratios for synergistic fermentation were performed, and Box-Behnken designs were adopted to optimize the fermentation conditions. The best combination of strains was confirmed as T. reesei RutC-30 and P. decumbens with an 8:2 inoculum ratio. The maximum sugar concentration was 1.48 g/L with CMCase (17.53 U/mL) and FPase (4.78 U/mL) in this situation. Response surface methodology revealed the optimized parameters as a substrate concentration of 5.93% at 32.12 °C, and a fermentation time of 5.85 d with a predicted sugar concentration of 2.91 g/L. Under these conditions, a maximum sugar production of 2.96 g/L was achieved in verification experiments.

The effect of polyethylene glycol (PEG) treatment was investigated relative to surface checks of red and Korean pine round wood for building Korean-style homes. The logs used for this study were impregnated with a solution of PEG-1000 for three weeks, and then they were dried to a moisture content of about 15% at the temperature of 120 °C within the drying time of 49 h. During the middle stage of drying, slight surface checks were found on red pine PEG-treated logs compared with severe surface checks on red pine control logs. Due to PEG treatment and high drying temperature, at the end of drying, apparent surface check was not found on red pine PEG-treated logs compared with serious surface checks on the corresponding control log. No surface checks were discovered on Korean pine logs during and after drying due to the PEG effect. Thus, PEG treatment was effective in preventing surface checks on red and Korean pine logs during drying at high temperature.

The surface chemistry of gravure printed décor paper and its effect on the adhesion of melamine formaldehyde (MF) coatings were studied. Two industrially printed decor papers with different designs were used for the study. A combination of the attenuated total reflectance Fourier transform Infrared (ATR FT-IR) and FT-IR spectroscopy techniques were employed to determine the effect of the gravure printing ink on the printed paper surface chemistry. Then, the influence of the surface chemistry on the adhesion of MF coatings was characterized according to the abrasion resistance test. The ATR IR results suggested that the printing ink components had a noticeable effect on the surface characteristics of the printed décor paper. In addition, it was indicated that the use of an organosilane adhesion promoter in the gravure ink formulation could significantly affect the adhesion strength of the MF coatings through the formation of ring siloxane structures. It seemed that siloxane bridges formed between the molecules of ink binder and UF resin could enhance the adhesion strength of subsequent MF coatings and could reveal better Taber abrasion resistance performance.

A porous, wood-fiber-based cushioning material for packaging was prepared in this study using poplar fiber and wood powder raw materials as an environmentally friendly resource. Water, the foaming agent azodicarbonamide and sodium bicarbonate, starch, and nucleating agent French chalk were used as additives, and the ingredients were subjected to hot-press molding. The effects of the initial water content on the foaming quality and mechanical properties of the plant fiber porous cushioning materials were explored. The results showed that the initial water content had a substantial influence on the foaming quality and mechanical properties of plant fiber porous buffer materials. When the initial water content was 69.3%, the initial embryo viscosity was the most suitable for bubble growth, and the porosity, pore size, and distribution of the samples were optimal. Furthermore, the mechanical properties of the samples were the strongest. The foaming mechanism of the plant fiber porous cushioning material was similar to the foaming mechanism of a polymer foaming material. Thus, the embryo viscosity had the greatest influence on the bubble growth process.