Research Articles

This paper investigated the possibility of using very fine wood chips for the production of P5 type building boards according to the EN 312 (2010) standard. Small wood chips are more evenly compressed during mat pressing because they have a high bulk density. Therefore, the beneficial effects of forming denser outer layers is lost. To achieve the desired shape of the density profile curve of a board, the moisture content of the chips used in the outer face layers was increased considerably (up to about 30%). As a result of the conducted tests, the mechanical properties of the manufactured boards met the EN 312 requirements for P5 boards above a density of 650 kg/m3. In cases when the additional conditions are being met, the standard requirements may be met at an even lower density level of approximately 550 kg/m3.

The colorability of wood veneers was evaluated with a natural dye that had been extracted using four different organic liquids. The solvent with the optimal dye effect was selected by measuring their total color difference. In addition, the dyeing mechanism, color fastness of water, and thermal stability of the dyed samples with the optimal dye effect were also investigated. The results showed that the absolute ethanol extraction can obtain dyed samples with a maximum total color difference accompanied with a satisfactory color fastness of water. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses suggested that only physical absorption occurred between the natural dyestuff and wood tissues, and the distribution form of natural dyestuffs was akin to the membrane covering the wood vessel wall, wood fiber lumens, ray cells, etc. Moreover, thermogravimetric (TG) results revealed that the residue of the dyed samples was more than that of the untreated samples, which indicated that the thermal stability of wood veneers can be improved after the dyeing process.

Palm-epoxy hybrid composites were fabricated by incorporating palm leaf stem stalk (PLSS) powder at levels of 0 wt%, 5 wt%, 10 wt%, and 15 wt%. Physical, mechanical, and erosion characteristics of these composites were investigated. Incorporation of filler powder had a positive effect on the hardness and impact strength and a negative effect on the tensile and flexural strength of the composites. The erosion test varied the impact angle (45° to 90°), impact velocity (40 m/s to 80 m/s), and erodent particle size (40 μm to 100 μm). The erosion experiments were statistically designed using Taguchi’s orthogonal arrays. It was found that the erosion rate of palm-epoxy composites decreased with increasing filler powder content, and that the composite filled with 15 wt% PLSS had the highest erosion resistance. The surface morphology of the eroded samples were examined using scanning electron microscopy.

The main objective of this research was to analyse the synergistic effects of impregnation agents that are most commonly used in plywood production on the strength of bonded joints. Two water-based impregnations (Teknol aqua 1410-01 and Cetol WV 885 BPD+) and one solvent-based impregnation (Gori 605) were used in this study. The tested adhesives were polyvinyl acetate (PVAC) ADHESIVE 3384 (1-component PVAC adhesive), EPI (emulsion polymer isocyanate) system 1920/1993, and polyurethane (PUR) 1968 (1-component PUR adhesive). Test specimens were made from European beech timber (Fagus sylvatica L.) for plywood production according to EN 205 (2017). Individual tests were conducted according to EN 204 (2001) for PVAC adhesives, and according to EN 12765 (2001) for PUR adhesives. Although the effect of impregnation on bond strength was demonstrated, it was different depending on the type of adhesive. A clear positive synergistic effect on the bond strength was shown for isocyanate-based adhesives in almost all of the tests. The synergistic effect of PVAC adhesive was very variable in each individual test and showed a negative influence of higher moisture content and dipropylene glycol content in solvent-based impregnation.

The effluent of a pulp mill was subjected to a biological treatment followed by ozonation to study the potential biodegradability improvement of recalcitrant compounds. Characteristics of the bio-treated pulp wastewater (BTPW) before and after the ozonation process were analysed by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, gel permeation chromatography, and gas chromatography, which detected the variations in the organic compounds in the effluents. Results showed that the ozonation treatment has the potential to turn some refractory compounds into biodegradable compounds and therefore increase the biodegradability of the BTPW. The increased biodegradability was accomplished because ozonation affects the structure of the refractory compounds and degrades the macromolecular organic matter into micromolecular organic matter. Furthermore, it is proposed that the degradation of macromolecular organic matter happens fast and therefore there are structural changes, since smaller molecules are formed. Then, these smaller molecules degrade over a longer period.

Effects of durian skin fiber (DSF), epoxidized palm oil (EPO), and cinnamon essential oil (CEO) on the physical and functional properties of polylactic acid (PLA) biocomposite films were investigated. The biocomposite films were produced via a solution casting process. The results indicated that the PLA with 3 wt.% DSF absorbed the maximum amount of water (5.9%), which was due to the hydrophilic characteristics of the DSF. Additionally, PLA and DSF lost the most weight after decomposing for 50 days in soil. The dart drop impact test showed a reduction in the impact failure weight of the PLA composites with EPO and CEO, which could have been because of their porosity; hence, a porosity was created between the microstructures. Interestingly, the tear resistance was remarkably amplified for the biocomposites with EPO and CEO. From the migration study, the PLA, DSF, EPO, and CEO biocomposite film appeared to be suitable for use as food packaging for all types of food, as there were no negative effects when they were tested with aqueous, alcoholic, acidic, fatty, and milk food product types.

To examine the effect of xylose concentration on butanol synthesis by Clostridium saccharoperbutylacetonicum, a kinetic model of acetone-butanol-ethanol fermentation in the media with various xylose concentrations (40 g/L to 60 g/L) was developed and implemented in COPASI. Batch fermentation experiments were conducted to feed and validate the model, and the highest butanol production was achieved in 45 g/L xylose medium. Strong correlations (R2 > 0.91) between model simulation and experimental results were obtained. The modeling results suggested that the reaction rates in R6 (from acetate to acetyl-CoA), R8 (from acetyl-CoA to acetoacetyl-CoA), R9 (from acetoacetyl-CoA to butyryl-CoA), R10 (from butyryl-CoA to butanol), R14 (from butyrate to butyryl-CoA), and R20 (xylose consumption) were higher in groups with an initial xylose of 45 g/L, 50 g/L, or 55 g/L than those in groups with 40 g/L or 60 g/L xylose. In contrast, the reaction rates in R13 (from butyryl-CoA to butyrate) and R16 (from biomass to inactive cells) were lower in groups with initial xylose of 45 g/L, 50 g/L, or 55 g/L than those in groups with 40 g/L or 60 g/L xylose, which indicated that when initial xylose concentration changed, those reactions were affected, which resulted in different butanol syntheses.

Smart lignin hydrogels with pH responsive and magnetic properties was prepared by free radical polymerization from lignin and acrylamide. In order to improve its swelling properties, calcium carbonate as pore-foaming agent was introduced to the polymer formulation, then magnetic particles (Fe3O4) was formed in the polymer by in situ reaction and co-precipitation. The results showed that degree of swelling of pH responsive hydrogels (PLH) containing the pore-foaming agent increased 47% compared to the original hydrogels (OLH) without pore-foaming agent, and the swelling rate of PLH reached 100% within 13.5 min under optimum pH conditions (pH = 6.8) which is a shorter amount of time, 1.5 times, compared to the OLH. The swelling-deswelling experiments showed that the hydrogels retained good reversibility and stability. Fourier transform infrared (FTIR) spectra indicated that the molecular chain of the PAM matrix hydrogels was successfully grafted on the lignin and the magnetic particles (Fe3O4) precipitated in the hydrogel. The X-ray diffraction (XRD) results showed that the magnetic particles in the hydrogels were composed of magnetite. The presence of a mesoporous structure was observed in scanning electron microscopy (SEM) images. The composition of hydrogels was analyzed by energy dispersive spectroscopy (EDS). The vibrating sample magnetometer (VSM) measurements also showed good magnetic properties.

Corn stover, which has a high non-structural sugar content, was treated by two-stage fractionation using water and acidified CaCl2 for the consecutive recovery of non-structural sugars and xylooligomers. In this process, water treatment under mild conditions (60 °C to 140 °C) was used for the recovery of non-structural sugars in the first stage, followed by the recovery of xylooligomers using acidified CaCl2 in the second stage under severe conditions (160 °C to 180 °C). For the recovery of non-structural sugars, a water treatment at 80 °C was observed to be effective, recovering 95.6% of the non-structural sugars. With a non-structural sugar-free solid, the reaction conditions for the second stage of treatment using acidified CaCl2 were statistically optimized. The highest recovery yield of xylooligomers (72.5%) was obtained under optimum conditions (172.9 °C, 22.2 min, 4.7% CaCl2). With the two-stage fractionation process, the glucan digestibility of treated solid was enhanced from 34.0% for untreated corn stover to 91.0% for the treated solid (with 15 FPU/g-glucan).

To understand the swelling effects of alkaline treatment on the morphological properties of fibers and physical properties of handsheets, bleached softwood kraft pulp was treated with NaOH at different concentrations. The results showed that the fiber swelling increased, but the shrinkage and elongation of the paper at a NaOH concentration of 6% or higher did not improve. Dissolution of amorphous material occurred during the treatment together with peeling reactions. The fiber length and shape factor decreased and the fines content increased with an increasing alkali concentration. The cellulose crystallinity decreased with an increasing NaOH concentration. This was confirmed by X-ray diffractometry, which also showed that some cellulose I was converted to cellulose II, especially at higher NaOH concentrations (> 9%). The fiber curl and kink indices increased and the handsheet density decreased with an increasing NaOH concentration. However, the tensile index decreased more steeply than the density with an increasing NaOH concentration, possibly because of the lower number and strength of the interfiber bonds, increased kinks, and reduced fiber strength and length. The handsheet extensibility first increased and subsequently decreased as the NaOH concentration increased, which indicated that well-controlled NaOH treatment could be used to improve the extensibility of paper.