Volume 10 Issue 2

The dimensional stability of thermally modified wood exposed to several wetting-drying cycles was analyzed. Specimens of dimensions 15×15 ×15 mm were thermally modified at 180 and 200 °C. The mass loss and chemical composition of the wood were determined in order to evaluate the effect and degree of modification. Afterwards, the radial, tangential, and volumetric swelling, anti-swelling efficiency, water absorption, water repellence efficiency, and mass loss due to wetting-drying cycles were determined and compared. The specimen’s mass tended to decrease with each additional rewetting cycle. Additional extractives that were formed via thermal decomposition leached out during wetting cycles. Thermal modification positively affected the dimensional stability of all investigated species. The wood’s swelling was reduced, a result attributed to hemicellulose degradation. Dimensional stability was improved by 24 to 30% following mild treatment and by 26 to 54% following more severe treatment. When specimens were exposed to six consecutive rewetting cycles, the swelling of the modified wood increased, whereas it slightly decreased for the control (hornification). The effective dimensional stability of thermally modified wood was reduced by 34 and 28.4% for beech, 47 and 19.6% for poplar, and 19.3 and 24.5% for spruce compared to the initial anti-swelling efficiency following the first wetting cycle.

To clarify how the fire resistance of ultra-low density fiberboards (ULDFs) was improved by the Si-Al compounds and to compare the effect of fire resistance between Si-Al compounds and fire retardant (chlorinated paraffin), the fire performance of ULDFs was evaluated by cone calorimetry. Comparing Si-Al compounds to chlorinated paraffin, the heat release rate (HRR), total heat release (THR), mass loss, total smoke release, and off-gases (CO and CO2) release of ULDFs treated with Si-Al compounds significantly decreased. However, when Si-Al compounds and chlorinated paraffins were simultaneously added, the mixed fiberboards showed the best results for peak of HRR (100.76 kW m-2), time to flameout (336s), THR (21.36 MJ m-2), and residual mass (34.26%). These results indicated that the Si-Al compounds had a significant effect on improving the fire resistance of ULDFs, and the Si-Al compounds and chlorinated paraffins have a synergistic effect in ULDFs.

Melamine-urea-formaldehyde (MUF) resin was synthesized by adding melamine with a first and second portion of urea, named M1 and M2, respectively. Different allocation proportions of M1:M2 (4:0, 3:1, 2:2, 1:3, and 0:4) were used to develop five MUF (MUF-1, 2, 3, 4, and 5) resins with an F/(U+M) molar ratio of 1.05. The chemical structures, curing behaviors, and cross-section morphology of the resins were characterized. Three-ply plywood was fabricated to evaluate wet shear strength and formaldehyde emission. Results showed that when the melamine allocation proportion was increased from 0:4 to 4:0, the total methylene ether group content increased, the curing rate was elevated, and a heterogeneous cross-section of the cured resin formed, which led to a wet shear strength increase of 42.11%. When the melamine allocation proportion decreased, the free melamine content increased, the pot life was prolonged, and a highly homogeneous morphology was formed, which resulted in a decrease of 42.86% in formaldehyde emission of the resulting plywood. These results suggested that a high melamine allocation proportion, meaning that more of the MUF resin was added initially, improved the water resistance of the resulting resin, whereas a low melamine allocation proportion decreased the formaldehyde emission reduction of the resulting plywood.

The influence of two polysaccharides, native corn starch and carboxymethyl cellulose (CMC), on the precipitation of calcium carbonate was examined by utilizing two different carbonation processes. In a batch process, carbon dioxide gas was fed through calcium hydroxide slurry at pH 11.5 to 12.0. The reaction was complete when the pH had been decreased to 7. In a fed-batch reaction, the carbon dioxide was dissolved in water while calcium hydroxide was pumped into the water, maintaining a constant pH of 6.0±0.5. Scanning electron microscopy, particle size analysis, and specific surface area analysis were used to characterize the structure of the precipitated calcium carbonate (PCC) pigments. In application testing, the impact of modified pigments on paper properties was examined. The results showed that carbohydrates can significantly affect the crystallization of calcium carbonate, but the influence depends on the precipitation conditions and the type and concentration of the carbohydrate added. The starch-modified PCC, produced by the fed-batch reaction, improved the mechanical properties of the paper, whereas CMC-modified PCC yielded paper with good surface and optical performance but weakened strength properties.

5-chloromethylfurfural (5-CMF) was produced from carbohydrates and lignocelluloses under the catalysis of Lewis acids. The millimole scale-up synthesis of 5-CMF from carbohydrates was successfully performed using metal chlorides or mixed metal chlorides as a catalyst in a heterogeneous system. The process involved the heating of the feedstock in a biphasic hydrochloric acid/organic solvent reactor over several hours. The process was later applied to raw biomass, which gave 5-CMF yields comparable to that of carbohydrates, based on the hexose content. It was found that mixed catalysts consisting of CrCl3 and ZnCl2 played an effective role in the transformation. The 5-CMF can be directly obtained in nearly 80% yield from the fructose under the mixed catalysts heterogeneous system. Bamboo pulp, eucalyptus pulp, and bagasse pulp were also directly converted into 5-CMF under this system at the yield of 32.7%, 36.2%, and 50.1%, respectively.

With the increasing scarcity of wood as a natural resource, bamboo has become a popular substitute for wood. The present work developed a high-strength original state multi-reorganization material (GPEHB), without the use of a hot press or traditional assembly. The original bamboo units were polygonized into outer contours and milled into finger-joints on each ending. The GPEHB was organized and assembled under an external press, using industrial adhesives. The mechanical properties and thermal insulation of GPEHB were characterized. Moreover, the overall GPEHB unit bending strength was 73.15 MPa, and the parallel-to-grain compression was 55.22 MPa (higher than that of Pinus sylvestris lumber, though less than that of glued laminated bamboo). The GPEHB unit overall density was 0.24 g/cm³, 76% lower than that of glued laminated bamboo, and 50% lower than Pinus sylvestris lumber. The compressive strength of GPEHB (7 units) was 170.5 kN, while the compressive strength of GPEHB for 14 units was 493.5 kN, which meet the requirements of GB 50005 (2003). The bending strength of GPEHB 7 units was 12 kN, while that of 14 units was 37 kN. The heat conductivity coefficient for GPEHB was 0.25 W/mK, which is better than concrete and steel. The GPEHB has taken full advantage of its honeycomb-structured material, which allows it to avoid stress concentration in the regular polygonal corners.

A knot is a natural defect that degrades the quality of softwood and hardwood veneer. To improve efficiency, the plywood industry needs a rapid, inexpensive method of knot identification that is easy to operate and industrialize. Although a non-contact knot-detection technology based on NIR spectroscopy and soft independent modeling of class analogy (SIMCA) has been successful in detecting softwood knots, it has not yet been explored in eucalypt (hardwood) veneer. This study investigated the interaction between knot size, spectral pretreatment methods, and wavelength range selections on this model’s classification accuracy of knots and normal eucalypt wood. The study found that classification results were accurate up to 94.4% for large knot samples (10 to 15 mm in diameter) and up to 100% for knot-free samples. Spectral data for small knots (< 5 mm in diameter) impeded the model’s classification accuracy because of confusion between small knots and both large knots and normal wood. Calibration models developed with second-derivative spectra exhibited the highest accuracy, followed by models built with first-derivative spectra, models based on spectra transformed by vector normalization, and the model based on the raw spectroscopy. Wavelength ranges of 1100 to 2500 nm enabled greater classification accuracy than wavelength ranges of 780 to 1100 nm or 780 to 2500 nm.

Acid dyes are often used to improve the decorative properties of bamboo products. However, the use of these dyes is problematic because they run easily. This study examined the use of chitosan as a fixing agent to address this issue. The study also investigated the interaction between dyed bamboo powder and dyed veneers pre-treated with chitosan. Powder was dyed at various pH values with acid scarlet GR and soaked in various solvents. Analyses were conducted using Fourier transform infrared spectroscopy, a zeta potential measurement analyzer, UV-visible spectroscopy, and a color measuring instrument. Pre-treated bamboo veneers were also dyed with acid scarlet GR and evaluated with the color measuring instrument, a scanning electron microscope, and an optical microscope. Chitosan functioned as a bridge and immobilized dye on the bamboo. This occurred through a chemical reaction and opposite charge attraction under acidic conditions. Pretreated dyed bamboo veneers demonstrated excellent dye uptake, color-fastness, and levelness. Therefore, chitosan shows promise for use as a fixing agent in dyed bamboo.

The demand of the global economy for fossil resources needed for the production of fuel and basic chemicals is expected to exceed supply in the coming decades. Because of its heavy reliance on fossil fuels for increased efficiencies over the 20th century, the chemical industry has been particularly motivated to harness alternative raw materials, such as biomass, that are environmentally and economically sustainable. Biorefineries have provided stable, large-scale means of converting biomass into base chemicals, but until recently the main focus has been on the conversion of the mainly cellulosic fraction of edible plants into biofuels. Second- and third-generation biorefineries are striving to be more economically integrated and sustainable by utilizing raw material fractions to a greater extent and by not competing with the agriculture and food sector. The goal of this study was to evaluate the potential of kiln-dry condensate as a source for production of bio-based chemicals. The condensates of three typical European wood species were analyzed. Part 1 evaluated the volatile extractives; Part 2 concentrates on semi- and non-volatile extractives of kiln-dry condensates.

Liquefied wood-based polyurethane wood coatings of an aesthetically acceptable light colour were prepared and characterised. Liquefied black poplar wood was obtained by solvolysis in a polyethylene glycol/glycerol mixture, and it was bleached with hydrogen peroxide. The bleaching treatment converted liquefied wood from a dark brown to a yellowish product. Polyurethane films were prepared by the curing of liquefied wood with polymeric diphenylmethane diisocyanate or trimethylolpropane toluene diisocyanate prepolymer (TMP/TDI) isocyanate-type hardeners. It was found that the selected properties of the films prepared from the bleached liquefied wood were, in general, equivalent to those prepared from unbleached liquefied wood. The mechanical properties of the films obtained with the TMP/TDI curing agent were acceptable for wood coating applications. The initial poor resistance of the films to water and ethanol was substantially improved by the addition of n-octyltriethoxysilane to the liquefied wood prior to the preparation of the polyurethane coatings; the hardness of the films also increased.