Volume 14 Issue 2

Wood dust samples with different particle sizes were used to investigate the explosion characteristics of wood dust. The dust samples came from Populus alba L., Pinus massoniana Lamb., and Cinnamonum camphora (L.) Pres., species that are commonly utilized in medium density fiberboard production in China. The thermogravimetric characteristics, element composition, and morphology of dust samples were analyzed to help explain the explosion phenomena in a 20 L sphere. The analysis showed that both the maximum explosion pressure and explosion index of wood dust presented a decreasing trend with increasing particle size, and the maximum explosion pressure values were in the range of 7 to 9 bar, regardless of species. For both explosion pressure and explosion index values, the wood dust with similar particle sizes were different, which are ranked as Populus alba > Cinnamonum camphora > Pinus massoniana. In addition, for the explosion pressure of wood dust with similar particle size, the dust concentration had threshold values. Additionally, the particle size and dust concentration had a synergistic effect on the explosion pressure and explosion index. Wood dust with a smaller particle size is more likely to explode at the threshold of concentration.

In the transition from petrol to bio-based chemicals, the total utilization of the components from biomass during the biorefinery process can be regarded as the key to its success. Currently, the lignin obtained from the biomass during the pulping of wood is burned; however, this component has the potential to be an alternative to petroleum for producing aromatic feedstocks. Additionally, glycerol is a by-product of biodiesel production. In this work, epoxy resins were synthesized from these two components in an environmentally compatible process using water as the reaction medium (as opposed to organic solvents). Base-catalyzed depolymerized lignin, the only depolymerized lignin available at a multi-kilogram-scale, was chosen as the lignin source. This depolymerized lignin acts as the curing agent for glycerol, which results in entirely bio-based resins. Depolymerized lignin imparts rigidity to the resins, and the glass transition temperature (Tg) increased as the lignin content of the resin increased. Thermogravimetric analysis (TGA) data showed that the resins had a relatively high thermal stability with the onset of thermal degradation starting at 281 °C.

This study details a comprehensive analysis of apple and grape pomaces that were generated in the course of juice and wine production, respectively. An extensive physicochemical analysis of these pomaces was performed to determine the elemental composition, ash content, sugar profile, and lignocellulose content. Scanning electron microscopy (SEM) images were taken to examine the morphology of the pomaces. Thermal stability was also examined using thermogravimetric analysis (TGA). Infrared spectroscopy was performed to observe the functional groups on the surfaces of the pomace samples. Grape pomace (GP) had better thermal stability than apple pomace (AP), but washing AP improved its thermal stability. The results from this study provide crucial information for various value-added applications of both apple and grape pomaces, especially for applications which are temperature-dependent. The diversion of these materials from waste back into the economic stream can alleviate their environmental burden and promote sustainable product development.

An effective method for microcrystalline cellulose (MCC) isolation from cotton stalk is reported. Cotton stalk was subjected to pretreatment and hydrolysis to determine the optimum conditions for isolating cotton stalk MCC (S-MCC). The main purpose of pretreating the cotton stalk with acetic acid was to remove ash. As a result, the ash content was reduced from 5.70% to 1.10%. After acid hydrolysis, the remaining ash was removed. Based on the single factor and orthogonal experiments, the optimum hydrolysis conditions were 85 °C, 1 mol/L HCl, 90 min, and a solid-to-liquid ratio of 1:10. The results showed that the reaction temperature and time strongly influenced the yield and size of the S-MCC particles. In addition to the yield, D90 was shown to be a good parameter to represent the degree of cellulose hydrolysis. The S-MCC had an ash content of 0.06%, α-cellulose content of 98.6%, moisture content of 4.64%, degree of polymerization of 146, and crystallinity index of 80.3%. These chemical and physical properties were comparable to those of commercial MCC. Other structural characterizations were determined by Fourier-transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy, and compared with commercial MCC.

This paper compares the characteristics and properties of wood from trees grown on forest land with trees grown on former farmland. The first generation of the tree stand, which was artificially introduced on lands previously used for farming, was accepted as an ecosystem on the former farmland. A total of 36 trees from 12 areas were chosen for the comparisons, where six areas contained former farmland and six contained forest land. The compared tree stands differed from each other only in terms of the growth conditions, i.e., forest and former farmland soils. Selected properties and characteristics of the tree tissue, including density, bending strength, wood static compression, thickness of the cell wall, and lignin content in the dry mass, were subject to analysis. The conducted research found significant differences in the analyzed variables between the compared tree groups. The pines grown on former farmland soil were characterized by a generally poor technical wood quality, thinner tracheid walls, and lower lignin content.

This paper examined the effect of machining parameters on surface roughness of medium density fiberboard (MDF) machined using a computer numerical control (CNC) router. The machining parameters such as spindle speed, feed rate, depth of cut, and tool diameter were examined for milling. The experiments were conducted at two levels of spindle speeds, four levels of feed rates, two levels of tool diameters, and two levels of axial depths of cut. The surface roughness values of MDF grooved by CNC were measured with stylus-type equipment. Statistical methods were used to determine the effectiveness of the machining parameters on surface roughness. The influence of each milling parameter affecting surface roughness was analyzed using analysis of variance (ANOVA). The significant machining parameters affecting the surface roughness were the feed rate, spindle speed, and tool diameter (p < 0.05). There was no significant influence of axial depth of cut on the surface roughness. The surface roughness decreased with increasing spindle speed and decreasing feed rate. The value of surface roughness increased with the increase of tool diameter.

Mechanical densification treatments make it possible to increase the density of low- or moderate-density woods, and thus a high mechanical strength of densified wood and high-value products can be obtained. The authors’ previous treatments showed that the diffusion and distribution of steam and the release of vapor inside densified wood were prevented to some extent during thermo-hydro-mechanical (THM) densification, causing the occurrence of protrusions, carbonization, blisters, and blows. This study aimed to overcome these problems. Based on the authors’ previous THM densification, different materials, such as fabric, metal mesh, metal foam, and sintered metal mesh laminate (SMML), were used to improve the process. Densification was tested on different wood species. The results showed that SMML was the preferable material for THM densification through enhancing diffusion and distribution of steam, and evaporation of moisture inside wood. No protrusion, carbonization, blisters, or blows were found after densification with SMMLs. The densified wood specimens showed uniform color and a neat surface.

Heat treatment is a modification method that has gained importance since the 1990s as part of the trend for more rational use of wooden materials. Heat-treated wood products are becoming more popular and have an established place in the market. For this reason, it is important to research applications for various wood types after heat treatment. In this study, Sorbus torminalis panels were first heat treated by the ThermoWood® method. Then, some physical properties (i.e., oven-dry density, air-dry density, shrinkage, swelling, 24-h water thickness swelling, and water retention), and mechanical properties (i.e., parallel compressive strength to grain, bending strength, and modulus of elasticity in static bending) were examined in ThermoWood® Sorbus torminalis. The results indicated that the physical property values of the heat-treated samples were lower than those of the control samples. Reductions of 14.4%, 12.1%, 64.9%, 49.3%, and 51.7% were observed for the oven-dry density (ODD), air-dry density (ADD), water thickness swelling (WTS), shrinkage (β), and swelling (α), respectively. Among the mechanical properties, there was a reduction in the bending strength (MOR) value, while the compressive strength parallel to the grain (CS) value increased up to 23.6% compared to the control samples. In contrast, no significant weight changes or changes in the modulus of elasticity in static bending (MOE) were observed.

Considering that many paper mills have modified their pulp manufacturing processes to produce dissolving grade pulps from a wide variety of woods, which can be used for the production of different end products, attempts have also been made to obtain highly purified pulps using several woods and non-timber as raw materials using chemical routes. This paper is an attempt to overcome the problem of the shortage of commercial timber for pulping purposes wherein non-commercial, widely distributed huizache, a woody plant, was evaluated as a raw material for the production of dissolving grade cellulose using an alkaline sulfur anthraquinone-methanol process with a pre-hydrolysis step and optimized conditions of the process. The pulp obtained from the cooking process was subjected to a sequence of elemental chlorine free bleaching. The pulp was analyzed for its performance during the pulping process, Kappa number, ISO brightness, contents of α, β, and γ cellulose, crystallinity index, degree of polymerization, and viscosity. The obtained results revealed high levels of all these parameters for the pulp produced from Acacia farnesiana, suggesting this plant could be considered as a raw material alternative for the production of dissolving grade cellulose, which in turn can be used to produce nanocellulose crystals.

High purity cellulose nanocrystals (NCCs) were obtained through the generation of various nanoparticle suspensions from different hydrolysis conditions of soluble grade cellulose (α-cellulose) prepared from huizache wood (Acacia farnesiana L. Willd.). These NCCs exhibited different surface morphologies and properties. Hydrolysis was carried out using both sulfuric and hydrochloric acids, while the methodology was based on 23 factorial designs of experiments. The obtained nanocrystals were characterized for particle size distribution, morphology, size of the NCCs, residual surface charge of the nanoparticles, and chemical composition using various experimental techniques. The two acid hydrolysis procedures produced NCCs suspensions that exhibited a unimodal or bimodal pattern of the Gaussian type, but differed in their properties. Average NCCs particle size obtained by hydrolysis with different concentrations (60 to 65%), at different temperatures (45 to 55 oC) and treatment times (45 to 65 mins) with H2SO4 acid and HCl acid were approximately 100 to 260 nm and between 75 nm to 512 nm, respectively, indicating influence of concentration and treatment time with both acids. Also, residual load analysis of sulphate groups in the NCCs suspensions in producing NCCs by H2SO4 hydrolysis revealed a minimum load of 39 mmol/kg and a maximum of 505 mmol/kg of NCCs.