Research Articles

An aromatic epoxy monomer, formed by glycidylation of gallic acid, was crosslinked by adopting different curing agents to obtain bio-based, crosslinked resins with suitable engineering properties. Specifically, tri- and tetra-glycidyl ether of gallic acid (GEGA) were obtained using a two-step synthesis. These bio-based monomers were cured in the following three epoxy formulations: a stiff cycloaliphatic primary amine, isophorone diamine, and a flexible polypropylene oxide amine (Jeffamine D-230). Next, the homopolymerization of GEGA was studied using an ionic initiator, N,N-dimethylbenzylamine, and a complex curing mechanism highlighted by calorimetric and mass spectra analysis. Calorimetric and rheological measurements were used to compare the curing behavior of the studied GEGA-based formulations. Mechanical properties of the gallic acid-based epoxy resins were comparable with those of standard epoxy resin formulations, based on di-glycidyl ether of bisphenol A. Thermogravimetric analysis of cured samples showed a relevant char content at high temperatures.

Mathematical equations were established and the following regularities of the plane milling process of wood materials were analyzed: effect of the cutting edge inclination angle on chip exit angle, influence of cutting edge inclination angle on speed of chip movement along the blade and exit speed of the chips from the cutting zone, dependence of the chip exit angle on the friction coefficients of the chips on the processed material surface and along the blade surface (friction coefficients were determined from the results of experimental measurements), and influence of mill rotation frequency on the chip exit angle. The milling of the chipboards with various mill designs was performed at different cutting parameters (diameter = 7 mm to 32 mm, number of cutting edges = 1 to 4, cutting edge inclination angle = -5° to 20°, frequency of mill rotation = 3000 min^-1 to 24000 min^-1, feed per tooth = 0.1 mm to 1.5 mm). The process of chip exit from the cutting zone was photographed, and the chip exit angles were measured. A comparison of the chip exit angle values obtained from the experiments with those from the calculations based on the developed mathematical equations showed a high convergence.

Environmentally friendly composites are increasingly used in building applications that require fungal and insect resistance. This study evaluated the ability of both wood-degrading and mold fungi to decompose hybrid composites made of wood furnish, glass fibers, and jute fabric skin. Fungal decay resistance tests employed brown-rot fungus (Fomitopsis palustris) and white-rot fungus (Trametes versicolor). Mold resistance tests were performed with a mixture of three mold fungi, Aspergillus niger, Penicillium chrysogenum, and Trichoderma viride. The test specimens were also bio-assayed against termites in both laboratory and field conditions. When compared to control composites specimens produced by conventional methods without glass fiber and jute, the specimens with/without glass fiber and jute fabric manufactured by the VARTM process showed high resistance against the wood-degrading fungi and termites under laboratory and field conditions; however, mold fungal growth was observed on the surfaces of the specimens with 10%, 15%, and 20% glass fiber (without jute fabric) and with 5%, 10%, and 15% glass fiber (with jute fabric). In geographical locations with severe decay and termite hazards, these composite products may have a long service life as alternatives to conventional composites.

Evaluating the safety of thermochromic inks for offset lithography in deinked pulp samples is a major area of investigation. In this study, three offset inks were analyzed – one that dries by absorption and two that dry by oxypolymerization of vegetable oils. Inks were printed separately on strips of white uncoated paper, and the prints were recycled by chemical deinking flotation. Thermochromic inks, handsheets, filter pads, and process waters obtained from deinking were tested for the presence of heavy metals, while concentrations of bisphenol A (BPA), total organic compounds, and antimicrobial agents were examined in handsheets and filter pads. The concentration of heavy metals cations was determined from ashes of undeinked and deinked pulp handsheets as well as from ashes of blank paper, flotation froth, and process water filtrates. BPA originates from thermochromic inks, and a 50% reduction of BPA was noticed in the samples after flotation. Considering the results, deinked pulp is undesirable due to the presence of BPA. Despite the presence of BPA, there was no release of toxic components from deinked pulp.

Three kinds of biochars were prepared using corn stalk as the raw material. Corn stalk degradation was achieved in solvents by treatment with prepared biochars for 5 h at 170 °C. The solvent systems contained ionic liquid and water components, which presented synergistic effects on lignocellulosic degradation. The oxidized alkaline biochar (B₂) was most effective for the lignin degradation in corn stalk, which promoted corn stalk dissolution into the reaction system. For treated corn stalk, both the lignin and hemicellulose were degraded during the reaction under the combined effects of biochars and nucleophilic components in solvents, and cellulose dissolution was enhanced. Dissolved cellulose was regenerated by mixing ethyl acetate and water gradually.

A delignification pretreatment is important for enhancing lignocellulose biodegradation. Alkali pretreatment is a promising approach. Fiber morphology, alkaline nitrobenzene oxidation, and ozonation were used to characterize the wheat straw modified by mild alkali pretreatment (2% sodium hydroxide (NaOH) at 121 °C for 30 min), and for studying the advantageous performance by Pycnoporus sanguineus NFZH-1 in the aspects of lignin and carbohydrate biodegradation. The results indicated a powerful and selective delignification in the mild alkali pretreatment process. The relative contents of the G unit and the T form both decreased with mild alkali pretreatment. Meanwhile, epicuticular wax removal and increased porosity was observed in the fibrous tissue of alkali-treated wheat straw. Thus, the biodegradation of the Klason lignin in alkali-treated wheat straw was clearly enhanced and reached 41.4% during the following 10 days of fermentation with P. sanguineus NFZH-1. In addition, the modification of fiber tissue with a mild alkali pretreatment enhanced the biodegradation of xylan. The biodegradation of the chemical constituents of the wheat straw was enhanced by the effective modification with a mild alkali pretreatment. The enhanced biodegradation will be helpful for improving the efficiency of straw return.

Scots pine and Norway spruce, the most used commercial wood species in Europe, were thermally treated under industrial conditions by steam (Thermowood®) and vacuum (Termovuoto). Matched boards were treated, and the alterations in chemistry, color, mass loss, mechanical properties, and durability were compared. In treatments at identical temperature and duration, Thermowood® and the thermo-vacuum process caused similar mass loss in both wood species. The thermal treatments showed minor effects on the released acetic acid during the thermal degradation of polysaccharides. The equilibrium moisture content correlated well with the mass loss and confirmed indirectly the similarity of the two processes. The chemical composition and durability of the two groups of treated wood were similar. In conclusion, Thermowood® and thermo-vacuum treatments according to Termovuoto technology both produce similar final products with regard to chemical composition, physical-mechanical properties, and durability, with some differences in the appearance.

Nanostarch has a small particle size and large surface area compared with traditional modified starch. In this study, nanostarch was prepared by dual screw extrusion and was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and X-ray diffraction (XRD). The nanostarch was studied as a coating adhesive in surface coating of lightweight coated paper. The crystallinity of nanostarch granules was decreased by dual screw extrusion, and its average particle size was about 100 nm. The results showed that for the paper coating formula of styrene butadiene latex and an ordinary oxidized coating starch ratio of 9:5, all ordinary oxidized coating starch and part of the styrene butadiene latex can be replaced by nanostarch. When 5 parts of ordinary oxidized coating starch and 4 parts of styrene butadiene latex were replaced by 6.5 parts nanostarch, the water retention property of nanostarch coating was increased by 64.0%, and its viscosity was decreased by 11.0%. The IGT printing surface strength of lightweight coated paper by the nanostarch coating was increased by 11.6%, and the glossiness of coated paper was increased by 7.2%. These results show that nanostarch surface coatings have good prospects for application in papermaking.

Methacryloyl chloride was grafted onto lignocresol to increase the acyl content of lignocresol and to enhance the interfacial compatibility of lignocresol and polylactic acid. The physical and mechanical properties of the modified lignocresol sample were studied. The methacryloyl-modified lignocresol was characterized by infrared spectroscopy (IR), ultraviolet-visible (UV) spectroscopy, and gel permeation chromatography (GPC). Unmodified and modified lignocresol samples were used to prepare composite films with polylactic acid, and its tensile strengths and elongations at breaks were analyzed after film formation. Thermal stabilities were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicated that methacryloyl group was successfully grafted onto lignocresol, and that the optimum dosage of methacryloyl chloride required was 0.5 mL per 0.5 g of lignocresol. When unmodified lignocresol was added to polylactic acid, the tensile strength gradually decreased as the amount of lignocresol increased. However, the composite films prepared from the methacryloyl-modified lignocresol exhibited a slower decline in tensile strength and displayed an increased elongation at break. The optimum mechanical properties were found using a 10% blend of modified lignocresol with polylactic acid.

Biofuel is an important alternative source of fuel, as many countries are looking to decrease their dependence on fossil fuels. One of the critical steps in biofuel production is the conversion of lignocelluloses to fermentable sugars, and there is need for cheaper and more efficient enzymatic strategies. Consequently, lignocellulase genes from various organisms have been explored. Termites possess varied sets of efficient micro-scale lignocellulose degrading systems. In this study, bacteria that degraded cellulose and xylan were isolated from termite gastrointestinal tract. The isolate was identified as Cellulomonas sp. by 16S rRNA gene sequencing. The bacterial enzymes cellulase and xylanase showed the highest activity at 50 °C and pH 8.0. The agricultural substrates were hydrolyzed by cellulases and xylanases, and more sugar was released from corn stover (18.903+0.65 mM/L) than from rice straw or cotton stalk. After direct hydrolysis and fermentation of agricultural substrates, ethanol (0.425+0.035 g/L) and lactate (0.772+0.075 g/L) were the major end products. Thus, termite gut bacteria can efficiently hydrolyze hemicellulose and cellulose, and these bacteria also have the potential to convert these fermentable sugars into valuable secondary metabolites.