Volume 11 Issue 1

In this paper, milled corncob powder was treated with sodium chlorite to remove lignin, and the resulting holocellulose was optionally modified with cationic agent. The derivative product was investigated using elemental analysis, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The influences of the dosage of the cationic agent, reaction temperature, particle size, dosage of paper strengthening agent, and pH value of the pulp on the paper physical properties were studied. The results indicated that cationic corncob holocellulose can improve the tensile index, burst index, and folding endurance of paper. When the dosage of cationic agent was 25% and the reaction temperature was set to 70 °C, the resulting tensile index, burst index, and folding endurance increased by 7.15%, 13.74%, and 55.95%, respectively, when compared with the control paper. The particle size of the raw material and the dosage of strengthening agent also greatly influenced the paper’s properties. The SEM analysis showed that the combination of fibers improved the strength properties of the paper after adding the strengthening agent. These results provide a method for value-added use of corncob waste.

Woody tissues consist primarily of a mixture of cellulose, hemicelluloses, and lignin. Covalent bonds between lignin and polysaccharides likely play a central role in determining the mechanical and physical properties of wood. Intact and defined lignin-polysaccharide networks have not been isolated in large quantities because of the recalcitrance of lignin, which demands harsh chemical treatments that alter its structure. This report presents a method for preparing large quantities of lignin-polysaccharide networks similar to those naturally present in wood based on the enzymatic oxidation of hemicellulose from Norway spruce. Fungal enzymes produced from various carbon sources were used to depolymerize these networks. The method was used for simulating “enzyme mining” – a concept in biorefineries, giving a possible explanation for its mechanisms.

The effects of citric acid on the curing properties of tannin-sucrose adhesives and on the physical properties of particleboard utilizing the adhesives were investigated. The citric acid content of tannin-sucrose adhesive was adjusted to 0.4, 1.8, 4.6, 13.8, 20.0, and 33.3%, which corresponded to pH values of the adhesive 40 wt% solution at 3.8, 3.0, 2.5, 2.0, 1.8, and 1.5, respectively. Thermal analysis showed that with increasing of citric acid content, the temperature of significant weight loss and the endothermic reaction of the tannin-sucrose-citric acid adhesive was reduced. When the adhesives were heated at 200 °C, boiled for 4 h, and adjusted to 20.0 and 33.3% citric acid content, the insoluble matter was increased significantly, and an absorption band derived from ester linkages and another peak, possibly from dimethylene ether bridges, were observed by FT-IR. The particleboards bonded with 20.0 and 33.3% citric acid adhesives at 200 °C satisfied the physical requirements of the type 18 Japanese Industrial Standards A 5908 (2003). Consequently, the addition of citric acid promoted the reaction between tannin and sucrose at a lower temperature, and the optimal hot pressing temperature decreased from 220 to 200 °C. The mechanical properties and water resistance of the particleboards were also enhanced.

Miscanthus, switchgrass, and softwood chip biochars, produced by slow pyrolysis, were characterized to evaluate their properties in light of potential alternative and novel applications. This work investigated specific physical and chemical properties of biochars that have not been previously reported. Atomic force microscopy (AFM), moisture absorption, and electrical and thermal analysis were conducted to demonstrate the mechanical, physical, and chemical properties of biochars. In addition, elemental analysis, specific surface area, Fourier transform infrared in the attenuated total reflectance (FTIR-ATR), and X-ray diffraction were performed. The state-of-art quantitative nano-mechanical measurement yielded a modulus of elasticity of approximately 10 GPa for the wood chip biochar, while the grass-based samples exhibited a comparatively lower modulus of approximately 5 GPa. In addition, the pore blocking phenomenon by water molecules was identified as a cause for atypical behavior of the biochars’ moisture absorptions, resulting in wood chip biochar having the lowest equilibrium moisture content of 6.2 wt.%. Results from electrical and thermal conductivity measurements demonstrated relatively lower values in comparison to carbonized biomass.

Ionic liquids have been employed to deconstruct and fractionate lignocellulosic biomasses because of their capacity to dissolve cellulose. However, there is limited literature reporting the use of ionic liquids in biomass saccharification, which mostly involves the addition of acid or water that conceals the true action of ionic liquid in saccharification. This article assesses the performance of molten Brӧnsted acidic 1-ethyl-3-methylimidazolium hydrogen sulphate ([EMIM][HSO4]) in saccharifying three agricultural biomasses, namely sago hampas, sugarcane bagasse, and rice husk, via saccharification kinetics. At 100 °C, [EMIM][HSO4] saccharification of the biomasses achieved equilibrium reducing sugar yields at various durations (sago hampas, 3 h; sugarcane bagasse, 1 h; rice husk, 5 h). The kinetic rate constant was obtained from model fitting, indicated that [EMIM][HSO4] showed a preference for saccharifying less recalcitrant sugarcane bagasse (37.9%) than sago hampas (7.0%) and rice husk (1.1%). Compared to H2SO4 saccharification, reducing sugar yields of [EMIM][HSO4] were consistently lower. The difference in yields might be attributed to the hydrous/anhydrous state of reaction and limited availability of component ions of the ionic liquid for dissolution and saccharification. This study demonstrates the feasible technical aspects of applying [EMIM][HSO4] to saccharify agricultural biomasses, which may lead to economic feasibility, recyclability, and cost effectiveness of ionic liquids in saccharification.

Thermal modification causes the darkening of wood throughout its cross-section because of chemical changes in the wood. After treatment, naturally light wood species look darker or even tropical, depending predominantly on the treatment temperature and processing time. This study investigates the suitability of using color measurement to determine treatment intensity at the industrial scale. The color was determined using the L*, a*, and b* color space, also referred to as CIELab, and the relationship between lightness (L*) and the color parameters (a*) and (b*) was investigated for thermal modification treatments at 190 and 212 °C. The wood species studied were pine (Pinus sylvestris L.) and spruce (Picea abies L.). The results showed that yellowness (+b*) and redness (+a*) had a significant prediction ability for class treatments at 190 and 212 °C, respectively. After treatment, there were no noticeable differences in color between the species, but sapwood was darker than heartwood in both untreated and thermally modified wood. The thickness of the boards had a proportionally darkening effect on the color values.

To investigate the possibility of using bamboo-bundle laminated veneer lumber (BLVL) as a cooling tower packing material, the water absorption rates, thickness swelling rates, and flexural properties of three different composite materials were studied. The BLVL was combined with either 12% or 24% phenol formaldehyde resin (PF), and the moso bamboo strips were exposed to water baths at three different temperatures (45, 65, and 85 °C) for 30 d. After the aging treatments, the 24%-BLVL samples showed lower water absorption rates and better bending properties than the other two composites. The temperature was found to have a significant effect on the modulus of rupture (MOR), modulus of elasticity (MOE), and the thickness swelling rate. As the temperature increased, the swelling rate and the rate of weight gain increased and the MOE and MOR decreased. According to the activation energies for swelling calculated from the Arrhenius-type plots, compared with the 24%-BLVL (22.95 kJ·mol-1) and the moso bamboo strips (12.69 kJ·mol-1), the effect of temperature on the swelling rate was greatest for the 12%-BLVL (24.15 kJ·mol-1). Results showed that the BLVL material is a promising candidate for a novel cooling tower packing material.

This article presents an investigation of the influence of selected factors (wood species, composition, and number of loading cycles) on the shear strength of laminated veneer lumber previously affected by cyclic loading. The monitored properties were determined on samples of European beech (Fagus sylvatica L.) and Eurasian aspen (Populus tremula L.). The laminated veneer lumber consisted of a combination of densified and non-densified veneers. Wood densification of up to 30% was carried out by means of rolling. The results show that each monitored factor significantly influenced the shear strength. The results also indicate a significant decrease in glued joint shear strength with increasing number of densified veneers in the laminated veneer lumber.

Effects of the addition of short carbon fibers (CFs) on the mechanical, physical, and morphological properties of polypropylene (PP) and wood-polypropylene composites (WPCs) were investigated. Hybrid composites (mix of wood and CFs) were manufactured in a two-stage process, pellet extrusion and samples mold injection with varying amounts of poplar wood fiber (0%, 20%, 30%, and 40%) and CFs (0%, 3%, 6%, and 9%), with and without maleic anhydride grafted PP (MAPP) as a coupling agent. The composites were prepared with extrusion blending followed by injection molding. The samples where then tested for mechanical and physical properties, and fractured surfaces where observed with scanning electron microscopy. The results indicated that the addition of CFs to WPCs improved the tensile and flexural strength and the modulus of elasticity but had only a small influence on elongation at break and impact strength. The density of hybrid composites slightly increased with CFs proportion but their water absorption was not affected. Scanning electron micrographs of the tensile fractured specimens showed improved adhesion of CFs and poplar with the PP matrix in the presence of a coupling agent.

Moisture content and temperature are two important process parameters that greatly influence the quality of biomass pellet fuels. The moisture content of raw material was varied at five levels (8%, 10%, 12%, 14%, 16%) to test its effect on water hyacinth pellet density and diametric compression strength. The experimental conditions included a compressing force of 6 kN, hammer mill screen size of 2 mm, and temperature of 100 °C. Five temperature conditions (80, 90, 100, 110, and 120 °C) were studied under the same conditions and 12% moisture content. In these conditions, the optimal moisture contents for water hyacinth pellet density and diametric compression strength were 12.2% and 11.5%, respectively, and the optimal temperatures were 100.4 °C and 104.3 °C, respectively.