Volume 14 Issue 2

Wood fibers were prepared as core materials for a vacuum insulation panel (VIP) via a dry molding process. The morphology of the wood fibers and the microstructure, pore structure, transmittance, and thermal conductivity of the wood fiber VIP were tested. The results showed that the wood fibers had excellent thermal insulation properties and formed a porous structure by interweaving with one another. The optimum bulk density that led to a low-cost and highly thermally efficient wood fiber VIP was 180 kg/m3 to 200 kg/m3. The bulk density of the wood fiber VIP was 200 kg/m3, with a high porosity of 78%, a fine pore size of 112.8 μm, and a total pore volume of 7.0 cm3·g-1. The initial total thermal conductivity of the wood fiber VIP was 9.4 mW/(m·K) at 25 °C. The thermal conductivity of the VIP increased with increasing ambient temperature. These results were relatively good compared to the thermal insulation performance of current biomass VIPs, so the use of wood fiber as a VIP core material has broad application prospects.

Neem (Melia azedarach) extract has good antibacterial properties, but its bioactivities are easily decomposed. In order to protect the bioactivities of neem extract, melamine urea formaldehyde (MUF) was used as wall material to prepare a wood microcapsule preservative. The size and distribution of microcapsules after treatments at different temperatures were determined by microscopy. These observations showed that increases in temperature caused the microcapsule particles to become smaller and more evenly distributed. The stability of this preservative was studied by use of an environmental factors experiment (ultraviolet light, condensation, and water spray) and a decay test. The results indicated that the microcapsule preservative from neem extract was more stable than the neem extract preservative. The results indicated that the microcapsule preservative from neem extract showed acceptable environmental stability. The water spray resistance of microcapsule preservative from neem extract was the best.

The huge rachis of Raphia matombe is intensely used by local people in Northern Angola for the construction of stools, chairs, shelfs, beds, or baskets. This is not only because it is a charming, fast-growing, renewable, and locally abundant material with a high aesthetic value but also due to its extremely light weight structure. Nevertheless, up to now the anatomical and mechanical features of rachises have hardly been studied, although monocotyledonous stem tissues have been the subject of numerous papers. This study presents an analysis of the rachis of Raphia matombe and its material gradients over its whole length and cross-sectional area. The modulus of elasticity increased from the inner towards the outer layers, whereas no clear axial gradient from the base to the apex was found. However, the specific modulus of elasticity increased from the base to the apex in relation to the density, reaching maximum values of 19.0 MPa/kgm-³. Still, the high anatomical and mechanical heterogeneity of the rachis impede quick and easy processing.

This study focused on a computerised TCM (tool condition monitoring) system as a part of automated monitoring of the machining processes in the wood industry. The system’s principal task was to evaluate the actual state of tool wear without disrupting the normal course of machine tool exploitation for cutting force and vibro-acoustic signals analysis. During the experiment, five physical quantities that are generated during machining were measured and recorded: cutting forces in two directions (Fx, Fy), ultrasonic stress waves (acoustic emission – AE), acoustic pressure in the range of audible frequencies (noise – N), and acceleration of mechanical vibrations (V). Six pairs of tools were used in the experiment. One tool from each pair was experimental, the other was a control tool. Out of the five physical quantities generated during machining that were tested as an indirect source of information on the tool condition, signals of cutting forces and mechanical vibrations proved the most useful. Both acoustic emission and noise signals emerged as wholly inadequate as evidence to predict tool wear.

Seaweed bio-composite films with different proportion of Lemang and Semantan bamboo microcrystalline cellulose (MCC) were fabricated via solvent casting. The seaweed/MCC composite films were flexible, transparent, and slightly yellow. The MCC particles further enhanced mechanical properties and opacity of films. The thermal stability of seaweed films was moderately improved upon addition of bamboo MCC particles. Bamboo MCC was found to be comparable to commercial MCC in reducing the water vapor permeability (WVP), water solubility (WS), and moisture absorption capacity (MSC) of seaweed films. The tensile strength (TS) of seaweed films was increased by 20 to 23% with addition of up to 5% MCC particles. In addition, bamboo MCC efficiently reduced the WVP of seaweed films comparable to commercial MCC particles. The WS of seaweed films was decreased by 10 to 19% with addition of 1% MCC particles loading. Lemang bamboo MCC (SB-MCC) was remarkably reduced the moisture absorption capacity (MAC) of films up to 25% with inclusion of only 1% MCC. Morphological analysis via Scanning Electron Microscopy (SEM) confirmed that there was homogeneous dispersion of MCC particles in the films. MCC particles improved the mechanical, thermal, and optical properties of seaweed films making them more suitable for food packaging applications.

Response surface methodology (RSM) was used to optimize the alkali pretreatment conditions for maximum fermentable sugar yield from sorghum pith with respect to NaOH concentration (0.5% to 2%), reaction temperature (20 °C to 40 °C), and pretreatment time (2 h to 20 h). The pretreatment caused a slight loss of glucan, but a significant removal of lignin and xylan from the pith, particularly lignin. The optimized results showed that the pretreatment conditions for the maximum predicted enzymatic glucose yield (90.5%) were 19.5 h, 2% NaOH, and 40 °C, while that for the maximum predicted enzymatic xylose yield (57.7%) were 9.9 h, 1.4% NaOH, and 37.5 °C. The optimized pretreatment conditions for the maximum total sugars yield were 16.2 h, 2% NaOH, and 37 °C, under which 72.4% of the glucan and xylan present in the raw material were experimentally hydrolyzed to release monomeric sugars. Additionally, with the optimized combination of 15 FPU cellulase and 7.5 CBU β-glucosidase per gram of pretreated material, the saccharification efficiency approached 90% glucan and 74% xylan present in the pretreated material (obtained at 37 °C for 16 h with 2% NaOH). This study may provide useful information for the development of novel alternative feedstocks for cellulosic ethanol production.

Effects of biological modification of Norway spruce wood with the wood-staining fungus Sydowia polyspora were evaluated relative to select physical and acoustical characteristics (PACHs), including the density (ρ), dynamic modulus of elasticity along the wood grain (EL), specific modulus (Esp), speed of sound along the wood grain (cL), resonant frequency (fr), acoustic constant (A), logarithmic decrement (ϑ), loss coefficient (η), acoustic conversion efficiency (ACE), sound quality factor (Q), and sound timbre. Incubation of the Norway spruce samples in S. polyspora lasted 12 w, 20 w, and 24 w. The results showed that the incubation time of spruce wood in S. polyspora did not have a statistically significant impact on most of the PACHs (ρ, EL, cL, fr, and A). However, biological modification of the spruce wood with S. polyspora had significant effects on the ϑ, η, and ACE. Treatment of the spruce wood with S. polyspora also changed the sound timbre, but the effects varied for each frequency.

An eco-friendly agent mainly consisting of activated glucose (AG) and citric acid (CA) was investigated for its potential wood modification applications. Scots pine (Pinus sylvestris L.) sapwood was treated with AG and CA both individually and in combination. The treatments with the combined agent resulted in an increase in the weight percent gain and decrease in the leaching ratio, which suggested a synergy between the two components for their fixation in wood. The dynamic vapor sorption behavior indicated an increased sorption at a higher AG concentration. Compared with the AG treatment, the CA treatment more effectively improved the dimensional stability of the wood. The modulus of elasticity was not influenced by the treatments, and the modulus of rupture was slightly reduced. Incorporation of AG in the CA inhibited the decrease in impact strength of wood compared to treatment with CA alone, which was a result of reduced crosslinking from the CA within the wood matrix. Fourier transform infrared (FTIR) spectroscopy revealed an enhanced absorbance, indicating development of ester bonds due to the treatment.

Mobile shields at woodworking machine workstations were considered in this work as part of a protection and accident prevention system. A shield design based on an aluminium frame is proposed. The results of the experimental tests demonstrated the high efficiency of material kick attenuation using the mobile shields, irrespective of their position and the filling used. Operational tests on the mobile shields were performed in a woodworking shop, which confirmed their usefulness and made it possible to supplement the conclusions with interesting observations concerning their dimensional and visual features, among other things.

Cellulose is a biodegradable, renewable material, and its chemical, crystalline, and thermal properties place limits on how it can be used in industrial applications. In this study cellulosic preparations made from bamboo were fractionated using a one-step process (EtOH-HNO3) or a two-step process (NaClO2 delignification and KOH treatment). Partial degradation of cellulose was observed in alkaline conditions. Although the crystal configuration was maintained, it was observed that the cellulose structure after delignification and alkaline post-treatment exhibited unique exothermic pyrolysis properties. By comparison, the acidic EtOH-HNO3 process efficiently removed hemicellulose and lignin from bamboo, achieving the highest purity of cellulose (96.8%) with the highest degree of polymerization (DP) value (815).