Research Articles

Despite bamboo’s noteworthy durability, the incidental effects of smoke treatment on the mechanical properties of bamboo culms, including its underlying mechanisms, have not been fully investigated. This study investigated the effects of smoke treatment on the flexural strength of Madake bamboo’s (Phyllostachys bambusoides) hierarchical structure. Results in small clear specimens displayed an asymmetrical flexural behaviour regardless of the applied treatment, and the parameters of flexural strain and specific energy absorption, demonstrated by modulus of elasticity and modulus of rupture, were found to differ. Concerning compression, parenchyma cells had good ability to absorb large deformation, indicated by their large increase in specific energy absorption. In addition, a distinct difference was found between smoke-treated bamboo and untreated bamboo as the capacity of its outermost fibres to withstand greater tensile load was impaired, indicated by the reduction in flexural strain. Thermal degradation caused an increase in the hydrophobicity of bamboo’s outermost layers, thereby engendering higher brittleness in the smoked bamboo. This work highlights critical changes in the mechanical properties of smoked bamboo, which can be addressed in future studies to improve its strength as a sustainable construction material.

Wood Science and Technology (WST) courses have been traditionally taught face-to-face in most of the universities worldwide, but the global COVID-19 pandemic has disrupted classroom lessons, replacing them with online teaching and learning methods. To assess the effectiveness of these online methods, a survey of students and academics were carried out in several Malaysian universities offering the WST programs. The survey revealed that students were mostly challenged by the problems related to access to internet, computer hardware, and lack of communication. Further, the student-centered learning method was preferred, while non-technical courses were the most suited for online teaching and learning. In contrast, academics appear to prefer pre-recorded lectures and recorded videos as the most common method for teaching online, while continuous assessment of the student’s progress found limited application. The results found that to enhance the effectiveness of teaching and learning online of WST courses, factors such as connectivity, student’s preparedness, content design, pedagogical approach, peer communication, and the teacher’s presence, must be taken into consideration and improved.

The SiO2/Al2O3 mole ratio, pore size, and acid sites are the key parameters of zeolite’s activity in lignin pyrolysis. In this study, the comparison of individual Y and M zeolites, the combined ‘Y + M’ sample after regeneration, and their effect on lignin pyrolysis were studied in five cycles (regeneration and reuse). The results were explained using Brunauer, Emmet, and Teller (BET), micropore surface area (MSA), and total acid sites (TAS) analyses. In comparison with the individual Y or M zeolite sample, the consistent higher catalytic activities of the combined ‘Y + M’ sample in repeated cycles were observed. Pyrolysis heavy oils were characterized by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The NMR analyses revealed that with increased zeolite regeneration cycles, p-hydroxy phenyl and methoxyl groups increased. Decreases in guaiacyl phenolic hydroxyl were less for the combined ‘Y + M’ sample than the individual Y and M zeolites. Lower weight average (Mw) of heavy oil for the combined ‘Y + M’ sample indicated the enhanced cleavage of lignin structures in pyrolysis. These results support the higher catalytic activity of regenerated zeolites for the combined ‘Y + M’ sample compared with individual Y and M zeolites due to the improved MSA and TAS.

To overcome the agglomeration tendency of nanosilver composite hydrogels and to improve their anti-mold properties, a method of preparing N-isopropylacrylamide/acrylic acid/nanosilver composite hydrogel was developed using the free radical polymerization method. The composite hydrogel was characterized via infrared spectroscopy, dynamic light scattering, transmission electron microscopy, and X-ray photoelectron spectroscopy in order to explore the effects of the acrylic acid content on particle size and dispersion properties of the composite hydrogels. The elemental composition, microstructure, and anti-mold properties of the bamboo strips treated with the composite hydrogel were also determined. The results showed that the composite hydrogel prepared using the novel method described in this study had good dispersity. Composite hydrogels with the smallest particle size and optimized dispersion were produced when AAc concentration was 0.64 µL/mL. The composite hydrogel effectively filled and covered the bamboo cells after treatment. Moreover, it displayed good anti-mold properties as well as retaining the color of the bamboo.

Different ionic liquids (ILs) and their mixtures with organic solvents (OSs) were investigated to determine their effects on pretreatment for enzymatic saccharification of pussy willow and Korean pine. Combinations of three ILs, namely (1-ethyl-3-methylimidazolium acetate ([EMIM]Ac), 1-butyl-3-methylimidazolium bromide ([BMIM]Br), and 1,3-dimethylimidazolium methyl sulfate ([MMIM]MeSO4)) and three OSs (N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO)) were used. Acremonium cellulase and Optimash BG were used for enzymatic saccharification. The viscosity of ILs and their mixtures with OSs was reduced by adding and increasing the OS amount in mixtures. The viscosity of [BMIM]Br was considerably decreased by the addition of OSs. For both species, the water-soluble fractions (WSFs) obtained using pure ILs decreased with increasing OS content in mixtures. For all co-solvent systems, the WSFs for pussy willow were twice as large as those for Korean pine. For both species, the yields of glucose and xylose were higher for [EMIM]Ac and its mixtures with OSs than for [BMIM]Br, [MMIM]MeSO4, and their mixtures. However, only small differences between glycan and xylose yields among the products pretreated by [BMIM]Br, [MMIM]MeSO4, and their mixtures were observed. The overall xylose yields for pussy willow were higher than those for Korean pine for all pretreatments because xylan is the main hemicellulose component of hardwood.

The adsorption and desorption properties of 12 resins containing flavonoid compounds found in Eucommia ulmoides Oliv. leaves (EUOL) extracts were investigated. The static adsorption and desorption, kinetic, adsorption, and thermodynamic properties of the adsorption of the flavonoids onto macroporous resins were determined. The HPD-300, NKA-9, and AB-8 resins exhibited a greater adsorption capacity and desorption characteristics. A pseudo-second-order kinetic model was suitable to characterize the kinetics of the adsorption of flavonoids onto the resins selected, and the diffusion of flavonoids was divided into three stages, with the boundary layer diffusion and intra-particle diffusion being the rate-controlling factors. The Langmuir model was found to be the best description of the adsorption behavior of flavonoids. Thermodynamic studies indicated that the adsorption of flavonoids was a physical, exothermic, and spontaneous process. The 60% ethanol eluted fraction from the NKA-9 resin column not only had the highest flavonoid content, but also possessed the strongest inhibitory effect on acetylcholinesterase. In addition, the degree of binding of the main flavonoid compounds found in the EUOL to acetylcholinesterase compounds was investigated via molecular docking technology. The results showed that the docking total score of isoquercetin and enzyme proteins were the highest, followed by kaempferol-3-O-rutinoside.

Three natural extracted oils from Citrus reticulata peels, C. aurantifolia leaves, and Linum usitatissimum (linseeds) were used as antifungal agents against the growth of Aspergillus flavus and Penicillium chrysogenum. The following main compounds (determined via gas chromatography–mass spectrometry) were found. The essential oil (EO) from C. aurantiifolia leaves contained limonene (22.96%), geranyl acetal (13.53%), and geraniol acetate (13.33%); the n-hexane oil from C. reticulata peels contained methyl-13-cyclopentyltridecanoate (16.74%), and D-limonene (16.06%); and linseed oil contained linoleic acid (27.36%), and oleic acid (19.01%). The inhibition of fungal growth significantly was reached 100% against A. flavus at all tested C. aurantifolia leaf EO concentrations and at a concentration of 2000 µL/mL for linseeds oil. The growth inhibition reached 100% against P. chrysogenum with C. aurantifolia leaf EO concentrations of 125-2000 µL/mL. Citrus reticulata peel EO had 100% growth inhibition of P. chrysogenum at concentrations of 2000 µL/mL and 1000 µL/mL, while linseeds oil had 100% growth inhibition at 2000 µL/mL. Thermogravimetric analysis showed that C. aurantifolia EO yielded the greatest thermal stability and color change protection to cotton pulp, while linseed oil was found to protect wood pulp-based and historical papers.

Measuring the energy consumption and evaluating the efficiency of machining processes is necessary for their optimization and for implementation of cleaner production. The final product quality and the machining process of woodworking are of great interest. The properties of thermally modified wood make it more resistant to fungi, moulds, and ligniperdous insects than natural wood, so it is increasingly used in interior and exterior spaces. This study examined the energy demand of the milling of heat-treated oak wood (Quercus petraea) by ThermoWood® technology. The investigated technological parameters were thermal modification temperature (160 °C, 180 °C, 200 °C, and 220 °C), cutting speed (20 m × s-1, 40 m × s-1, and 60 m × s-1), feed rate (6 m × min-1, 10 m × min-1, and 15 m × min-1), and the material of the cutting tool. As the temperature of the thermal modification increased, the cutting power decreased due to a chemical degradation due to heating and reduced wood density. The lowest energy consumption was observed for the milling of wood treated at 220 °C with a cutting speed of 20 m × s-1, and a feed rate of 6 m × min-1.

Diphenols with structures similar to bisphenol A (BPA) were designed and synthesized from three kinds of lignin oxidative depolymerized derivatives (LODD) to investigate the substitution possibility of BPA by LODD as raw material. The chemical shift and integral area of nuclear magnetic resonance spectra and the X-ray photoelectron spectroscopy analysis results showed that phosphorus- and nitrogen-containing diphenols were successfully formed. The cone calorimeter test and thermogravimetric analysis exhibited that the epoxy resin from diphenols were typical intumescent flame retardancy systems. These results showed drastically improved flame retardancy compared with traditional epoxy resin. Among them, the epoxy resin derived from vanillin presented the best flame retardancy properties. Due to a phosphorus-rich carbon layer being formed and accumulated at the surface of the epoxy resins from diphenols, the thermal degradation showed great enhancement of the char residues.

Embossing is a commonly used design element on printed products and packaging. It enhances the product impression with optical and haptic effects. The material deformation during the embossing of cardboard is normally done using high mechanical pressure between two dies. The use of ultrasound in the embossing process leads to a noticeable reduction of the embossing pressure and a greater embossing precision. However, there is a noticeable heating of the cardboard during the ultrasonic-assisted embossing process. This work aimed to characterise the effects of heating and to understand the reasons for the greater precision with decreased force when ultrasound is used. Therefore, the effects of the thermal ultrasonic energy on the chemical composition and the morphological properties of the fibres were investigated. The findings showed that no noticeable changes occurred in the chemical composition or fibre geometry as a result of the embossing process with ultrasound.