Research Articles

The bark of Goupia glabra trees grown in a native forest area in the Amazon region of Brazil was anatomically and chemically characterised for potential use as a chemical source for bio-refineries. The bark is silvery-grey to reddish-grey, with a scaly rhytidome composed of 2 to 3 periderms with a small phellem content. The phloem has abundant sieve tube members and a conspicuous presence of sclerified nodules of fiber-sclereids or sclereids; no fibers were observed. The bark had the following average composition (dry mass): 5.2% ash, 24.6% total extractives, 1.1% suberin, and 43.8% total lignin. The polysaccharide composition showed a high ratio of xylan hemicelluloses to cellulose. The ethanol-water bark extract showed high antioxidant capacity. The chemical characterisation of different granulometric fractions showed that extractives were present preferentially in the finest fractions, particularly with enrichment in ethanol solution.

This paper investigates the impact of the global economy on the forest-based sector in Slovakia in the early years of the 21st century. Indicators such as gross domestic product, production value of forestry-wood sectors, net exports, foreign direct investments, and the ratio indices of foreign direct investment to GDP in industrial production and foreign direct investment to production value were used to analyze this sector in the context of globalization. Multiple regression analysis was used to determine the factors that significantly affect the development of the forest-based sector and to shed light on how globalization impacts the analyzed sector. The results showed that the forest-based sector had a minor impact of the Slovak economy with less than 5% share on the whole GDP. Using multiple regression analysis it was found that globalization factors such as foreign direct investment and net export did not have a significant influence (p > 0.44175) on the forest-based sector during the investigated period. Nevertheless, the highest globalization indicators were detected by the pulp and paper industry ( = 2.72; 29.14) and the furniture manufacturing ( = 1.60; 27.57). The highest variability of FDI was identified in the forest sector (vx = 72.38%; 67.32%) by influence of zero FDI in the last three years and in the wood industry (vx = 38.90%; 38.51%).

The thermal characteristics of Paulownia sawdust (PS), bamboo sawdust (BS), rice lemma (RL), and corncob (CC) in an oxidizing atmosphere were investigated using thermogravimetric analysis. The results indicated that the reaction of biomass oxidative decomposition took place in two main phases: devolatilization and char oxidation. Among various types of biomass, BS was found to possess the highest oxidative decomposition reactivity followed by PS, CC, and RL. Additionally, an increase in heating rate led to a significant improvement of the reactivity. The kinetic modeling of the oxidation reaction with the direct fitting method using the DRPM model showed a satisfied match with the experimental data, and the activation energy of biomass during the devolatilization process was higher than that of the char oxidation process. The activation energy of devolatilization was in the range of 80.7 to 133.8 kJ/mol, while that value of char oxidation fluctuated between 41.7 and 67.5 kJ/mol. In addition, with an increase in the heating rate, a marked compensation effect between the activation energy and pre-exponential factors was observed.

A normal temperature cured starch-based wood adhesive was prepared using dry method esterification and polyisocyanate prepolymer crosslinking. The effects of esterification and crosslinking on the properties of corn starch adhesive were investigated. The esterified starch and adhesive were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), dielectric analysis (DEA), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that maleic anhydride (MAH) esterified starch was obtained using dry method esterification. After esterification, the crystal type of starch did not change, but the crystallinity of starch decreased. The distribution of adhesive at the bonding interface was improved after esterification. The prepolymer improved the thermal stability of the adhesive, and the optimal addition of prepolymer was 10%.

The effects of acid copper chromate (ACC) and hydrothermal treatments were determined relative to the hardness, decay resistance, and dimensional stability of poplar wood. Test specimens, prepared from poplar wood (Populus nigra L.), were first heat-treated under saturated steam in a digester and then impregnated with ACC solution and by a long-term (21 days) dipping technique to reach complete saturation. Impregnated specimens were exposed to white-rot fungus (Trametes versicolor) for 14 weeks, using the Kolle flask method. The weight loss and Brinell hardness were determined after impregnation, thermal treatment, and exposure to T. versicolor. The combination of thermal treatment and ACC preservative on the poplar wood showed improved hardness and decay resistance properties of wood, depending on the treatment time and temperature. The highest weight loss (37.78%) was observed for control specimens, and the lowest (3.03%) occurred in 1% ACC-treated specimens. The highest Brinell hardness on a tangential surface was observed in 1% ACC-treated specimens (6.45 kN), and the lowest was noted in the specimens heat-treated at 130 °C and 180 min (0.52 kN).

The surfaces of kenaf core fiber (KCF), oil palmempty fruit bunch fiber (EFBF), and oil palm mesocarp fiber (OPMF), were chemically modified using 5 wt.% aqueous sodium tetraborate decahydrate (borax) solution to enhance their hybrid fiber interface bonding with a polylactic acid (PLA) matrix. The untreated fibers (KCF, EFBF, and OPMF) and treated fibers (BXKCF, BXEFBF, and BXOPMF), were examined using chemical analysis, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The treatment caused minimal removal of lignin and significant elimination of hemicellulose and waxy substances. The treated and untreated KCF (5%), as a secondary fiber, was randomly mixed, respectively, with treated and untreated EFBF and OPMF (55%), melt-blended with PLA (40%), and subsequently compression-molded to form hybrid fiber-PLA biocomposites. The resulting composite is aimed to exhibit improvements in its mechanical properties and dimensional stability. The optimum results for tensile and flexural properties, as well as water uptake and thickness swelling, were observed for the borax-treated fibers in comparison with the untreated fibers. The BXEFBF-BXKCF-PLA biocomposites exhibited the best results. This work demonstrated that aqueous borax modification of natural fibers could offer a possible option to the most common mercerization method.

Cross-linked cellulose microspheres (CL-CMs) were successfully prepared using an inverse crosslinking suspension method from a cellulose solution with sodium hydroxide/urea aqueous solution as a solvent and epichlorohydrin as the crosslinker. The effects of epichlorohydrin content on the appearance and dispersity, average pore volume, moisture content, and wet real density of CL-CMs were studied. The microspheres presented a good spherical shape and porous surface structure. After activation with NaIO4, the recombinant protein A was immobilized onto the surface of CL-CMs to form an immunoadsorbent. Adsorbents containing various amounts of protein A were applied to adsorb immunoglobulin G (IgG) from human plasma. The maximum IgG adsorption capacities with static adsorption and dynamic adsorption were 23 and 13 mg, respectively, per gram of CL-CMs carrying 6.8 mg of recombinant protein A. Therefore, CL-CMs immobilized with recombinant protein A have great potential for application in the field of blood purification.

The interaction among three biomass components (hemicellulose, cellulose, and lignin) in an autoclave was studied based on the extreme vertices of a constrained region that had a significant effect on the distribution and characteristics of the products. The mathematical model of the three components was established according to the yield distribution. Based on the model, the biomass components and the hydrothermal characteristics of biomass were predicted. Subsequently, the contents of the main biomass components were analyzed, thus eliminating the complicated testing process and providing a convenient and reliable calculation tool for determining the three biomass components. The gaseous products showed that products from cellulose hydrolysis promoted hemicellulose hydrolysis and generated large amounts of CO2. The lignin content, as well as the low cellulose and hemicellulose contents, inhibited the acids and ketones in light oil. In addition, the interaction among cellulose, hemicellulose, and lignin inhibited the production of acids in heavy oil and promoted phenolic synthesis. A series of hydrolysis product reactions such as polymerization and condensation were increased to produce a char at a high degree of aromatization by the interaction among the three components.

The crystallinity and acoustic-vibration parameters of Picea jezoensis, including specific Young’s modulus (E/ρ)coefficient of sound-radiation resistance (R), sound resistance (ω), and the ratio of Young’s modulus to the dynamic stiffness modulus (E/G), before and after heat treatment were measured and characterized. Conditions for the heat treatment included N2 as the protection gas and temperatures of 170 °C, 190 °C, and 210 °C with holding times of 2 h, 3 h, and 4 h. The results showed that specific Young’s modulus, the coefficient of sound-radiation resistance, and the ratio of Young’s modulus to the dynamic stiffness modulus ncreased, whereas sound resistance decreased, thereby improving the acoustic performance of the wood. The maximum increments were 5.7% for specific Young’s modulus (210 °C, 3 h), 8.8% for the coefficient of sound-radiation resistance (210 °C, 3 h), and 13.8% for the ratio of Young’s modulus to the dynamic stiffness modulus (210 °C, 4 h). Conversely, the maximum decrease in sound resistance was 5.6% (170 °C, 2 h). The crystallinity of heat-treated samples universally increased, and the maximum reached 60.67% (210 °C, 4 h), which was 9.9% higher than that of the control group. Moreover, the sound resistance decreased within increasing crystallinity growth, indicating that these two parameters were negatively correlated. Overall, the acoustic-vibration performance of P. jezoensis was improved through heat treatment, with the best vibration performance obtained at 210 °C with a holding time of 4 h.

Transforming waste or recycled materials into value-added products is of high priority today. Wood plastic composites (WPCs) show high potential for the use of recycled materials in making durable composites. The applicability of WPC panels produced from recycled materials (ultralight foam core particleboards) for exterior building application was tested using wood-destroying basidiomycetes. The results showed that the panels were fully resistant against Coniophora puteana (Cp) and Gloeophyllum trabeum (Gt), but not very resistant against Pleurotus ostreatus (Po). The decay susceptibility index of Po-exposed specimens showed that the polystyrene-bonded (PS) samples were more resistant than solid beech wood samples that were used as references, followed by melamine-urea formaldehyde-bonded samples. A comparison with the reference samples also showed that the panel density had a significant influence on the panel’s resistance against basidiomycetes. The higher the panel density, the more resistance will be achieved in the panel.