Volume 11 Issue 2

This study describes changes in the viscoelastic and thermal properties of composites made with various percentages (up to 20 wt.%) of a natural fiber blend (a mixture of flax, kenaf, and hemp fibers) and polyamide 6 (PA 6). According to the differential scanning calorimetry (DSC) analyses, the incorporation of natural fibers produced minor changes in the glass transition (Tg), melting (Tm), and crystallization temperature (Tc) of the PA 6 composites. Because of the reinforcing effect of natural fibers, the storage modulus (E’) from dynamic mechanical thermal analysis (DMTA) increased as the natural fiber content increased. The E’ values at room temperature and Tg were 3960 MPa and 1800 MPa, respectively, with the incorporation 20 wt.% fiber, which were 68% and 193% higher than the E’ value of neat PA 6. As the natural fiber content increased, the thermal stability of the composites decreased, and thermogravimetric analysis (TGA) showed that the onset temperature of rapid thermal degradation decreased from around 440 (neat PA 6) to 420 °C (20 wt.% natural fiber blend). The addition of 20 wt.% single type fibers showed comparable DSC and TG results to the incorporation of 20 wt.% natural fiber blends.

Thermoplastic epoxy resin (TPER)-based composites containing different amounts of ultra-fine cellulose (UFC) were prepared via melt compounding and injection molding. The effect of UFC loading on the mechanical properties and dynamic rheological behavior of the UFC-filled TPER composites was analyzed. The UFC-filled composites displayed higher complex viscosities than those of the neat TPER composites, especially at low frequencies. The elastic modulus of the 20 wt.% UFC-filled composite was up to 6- and 2-fold higher than that of TPER at 0.1 and 100 Hz, respectively. The loss factor decreased over the entire frequency range with the incorporation of UFC. The tensile modulus of elasticity (TMOE) of neat TPER was 3.13 GPa, and it increased as a function of UFC loading. The neat TPER exhibited the lowest flexural strength (108.1 MPa), and the flexural strength increased by 14% with the incorporation of 20 wt.% UFC. The results of the TMOE and the flexural modulus of elasticity (FMOE) were in agreement with rheological data on complex viscosity, elastic modulus, and viscous modulus. Ultra-fine cellulose-filled TPER composites may provide special capabilities for automotive applications and may also meet requirements for end-of-life vehicle (ELV) directives.

Wood preservative treatments are indispensable for wood used in severe environmental conditions. Decay occurs in preservative-treated woods due to the poor impregnation of sapwood; this problem has recently gained attention for Cryptomeria japonica kiln-dried logs. To clarify the causes of this phenomenon, the influence of drying temperature on the penetration of preservative into sapwood logs was investigated. Sapwood samples taken from logs dried at 20 °C to 120 °C were impregnated with copper azole (CuAz). The bordered pits of these samples were observed by scanning electron microscopy (SEM). These results revealed that CuAz absorption decreased with increased drying temperature. The CuAz penetration was deepest for the samples dried at 20 °C. The occurrence of neutral-position bordered pits tended to decrease with increasing drying temperature. These results indicated that there is a strong relationship between the drying temperature and the appearance of bordered pits. Furthermore, the preservative permeability decreased with increasing drying temperature. This result implies that one factor restraining fluid permeability is the aspiration of bordered pits.

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.