Volume 14 Issue 3

Trichoderma viride can infect wheat straw composites (WSC), thus affecting the quality of boards. This study investigated the change in color of the composite and its chemical composition after the straw was infested with mold with for 4, 8, or 12 weeks. Fourier transform infrared spectroscopy (FTIR) and high-performance liquid chromatography (HPLC) were used to analyze chemical structural changes in the WSC after the infestation. The infested surface and core layers were examined and analyzed. The infection of T. viride on the WSC can darken its color. After 12 weeks of cultural infestation, 19.6% of cellulose, 27.2% of xylan, 9.3% of lignin, and 31.9% of ethanol extracts were degraded. The degradation on WSC by T. viride was 9 times and 14 times more than the degradations of pine and poplar wood, respectively. T. viride attacked WSB differently on its surface and center layers. More lignin in the WSB surface layer was degraded. In contrast, cellulose and xylan were degraded to a greater degree in the center.

Due to certain problems with petroleum-based products, the development of a renewable and green adhesive is urgent and important. Yeast hydrolysate, which contains more than 55% protein, possesses many advantages in its source (it originates from yeast as opposed to petroleum) and environmental protection. In this work, a wood adhesive based on yeast hydrolysate was developed through the addition of sodium dodecyl sulfate (SDS), polyvinyl alcohol, and ethylene glycol diglycidyl ether (EGDE) to improve properties of the yeast hydrolysate adhesive via the epoxy group in EGDE. The influence of EGDE on the adhesive properties (density, viscosity, solid content, bonding strength, and curing temperature) was investigated. The thermal property and changes in molecular structure during curing were characterized via differential scanning calorimetry and Fourier transform infrared spectroscopy, respectively. These results indicated that a ring-opening reaction between the epoxy group of EGDE and the active group had an important influence on the properties.

The effects of some pulp additives on mechanical, optical, and antifungal (Aspergillus terreus Ate456, A. niger Ani245, and Fusarium culmorum Fcu761) properties of papersheets produced from linen fiber pulp were evaluated. The ground materials (80 mesh) of Pinus rigida wood (PRW), Costus speciosus rhizomes (CSR), and Senegalia catechu rhizomes (SCR) were used as pulp additives at the concentrations of 0, 1, 2, and 4%. Papersheets with PRW at 2 and 4% as pulp additives had significant effects on tensile index with 26.41 and 30.22 N.m/g; burst index with 2.91 and 2.92 kPa.m2/g; and tear index with 2.52 and 2.53 mN.m2/g, respectively. The highest (64.36%) and lowest (62.90%) percent of brightness was observed in paper sheets produced from pulp without additives and CSR at 4%, respectively. Scanning electron microscopy showed that the produced papersheets with plant source additives had different degrees of decaying patterns, except for papersheets with PRW as additive, which showed some inhibition against the fungal growth. In conclusion, the mechanical properties of papersheets were significantly enhanced by the addition of the three pulp additives.

The correlation between the bending elastic modulus of lumbers along the primary direction and that of the resultant cross-laminated timber (CLT) plates in the full size suitable for slabs or wallboards was investigated to verify the feasibility of predicting the bending performance during the manufacturing of heavy building structures of this new type of material. A batch of Canada hemlocks lumber was graded based on a vibrational test that measures longitudinal elastic modulus. The elastic modulus and shear modulus in the transverse direction were also measured using the scheme of a torsional modal analysis of a cantilever plate. CLT were fabricated using the graded lumbers in sizes suitable for slabs or wallboards. The elastic moduli of these CLT products were measured using a conventional four-point static bending test. Finally, the static measurements of the elastic moduli of the CLT were compared with their predicted values that were calculated with the aforementioned data collected from the lumber pieces. The predicted elastic modulus along the primary direction of a CLT product agreed with the measured values. Therefore, the mathematical model of the CLT plate and the equation of its elastic modulus are feasible for the bending performance prediction in industrial production of CLT.

The enzymatic hydrolysis of cassava residue treated by a hot water (HW) pretreatment, an extreme-low acid (ELA) pretreatment, and an alkaline hydrogen peroxide (AHP) pretreatment was investigated. The results showed that the ELA pretreatment dissolved greater xylan and glucose quantities than the HW pretreatment under the same conditions, and the xylan and glucan contents of the pretreated substrate affected the subsequent cellulase hydrolysis. The conversion to glucose by cellulase hydrolysis reached 81.4% after the HW pretreatment, while the glucose yields under the ELA and AHP pretreatment conditions were 78.3% and 71.0%, respectively. In addition, supplementation with xylanase improved cellulase efficiency. At an equal xylanase dosage, a higher glucose yield (i.e., 91.3%) was achieved for the ELA-pretreated substrates that contained a lower xylan content. Xylanase supplementation in the AHP pretreatment had little effect on the glucose conversion. Finally, X-ray diffraction studies showed that the HW and ELA pretreatments increased the cassava residue crystallinity, while the AHP pretreatment had little effect.

A shortage in the rubberwood supply is becoming a reality in Malaysia. To find alternative raw materials for Malaysian wood-based industries, fast-growing species have been identified and need to be analyzed in particleboard manufacturing. This study evaluated the properties of particleboard made with a 50:50 ratio of Neolamarckia cadamba and Leucaena leucocephala with melamine urea formaldehyde as the resin at different contents (10%, 12%, and 14%) and particle sizes (1.0 mm, 2.0 mm, and unscreened particles). The particleboards were tested according to EN 312 (2003). The results showed that the particleboard mechanical properties were significantly improved with increase of the resin content and particle size. The thickness swelling value dropped as resin content was increased, showing better stability of the board.

The deconstruction of cellulose, hemicellulose, and lignin has varying effects on lignocellulosic biomass. To understand and evaluate these effects it is important to conduct compositional and structural analyses. In this study, the effect of different pretreatments on the composition and structure of water hyacinth (WH) was investigated. The pretreatment methods investigated were acid, alkali, ionic liquid (IL), and microwave-alkali. The structural analysis was completed before and after the pretreatment using scanning electron microscopy. In addition, the biomass recovery rate was measured to evaluate the composition of the WH biomass. Based on the results, all pretreatment methods effectively disrupted the crystalline structure and enhanced the digestibility of the WH through increasing the cellulose and hemicellulose content and reducing the lignin content. The acid pretreatment resulted in high cellulose digestibility while the microwave-alkali pretreatment destroyed only the lignin structure of the WH. The alkali and IL pretreatments increased the cellulose and hemicellulose content of the WH. The highest recovery rate was obtained via IL pretreatment. The acid, microwave-alkali, and alkali pretreatments had the second, third, and fourth highest recovery rates, respectively. This study showed that the biomass recovery rate, compositional makeup, and structural analysis are important to use WH for bioenergy production.

Novel lignin-based polyurethane (LPU) and LPU-nanosilica composite films were prepared using in situ polymerization. The effects of various nanosilica contents on the structure and properties of the LPU matrix films were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), dynamic thermomechanical analysis (DMA), tensile test, and contact angle measurements. The results showed that hydrogen bonding and cross-linking occurred between the -N-H and -C=O functional groups in the LPU-nanosilica films. Morphological and surface energy analyses showed uniform dispersion of amine modified silica nanoparticles in the LPU matrix at low concentrations. The incorporation of silica nanoparticles considerably improved the thermal stability and mechanical properties of the LPU films because of the introduction of silicon-oxygen bond between the LPU matrix and nanosilica. Overall, the introduction of small amounts of silica nanoparticles could improve the properties of the renewable LPU films, which are useful in the development of biomaterials.

An effective cellulose/MoS2 (Ce/MoS2) composite was synthesized via a one-pot microwave-assisted ionic liquid method for the photocatalytic reduction of toxic Cr(VI). Effects of ionic liquids (ILs) on the MoS2 nanostructure were considered, and the obtained composite was characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometry (XPS), and electrochemical impedance spectroscopy (EIS). The results indicated that the MoS2 nanoplates were anchored and dispersed on the surface of the cellulose. Compared with the pristine MoS2, the support of the cellulose greatly enhanced the photocatalytic reduction efficiency of Cr(VI) ions in solution, from 65.9% to nearly 100%. The reduction mechanism was considered, and the results implied that the simultaneous reduction of Cr(VI) during the initial dark adsorption process was observed due to the effect of citric acid as a hole scavenger. Finally, regeneration tests revealed that the Ce/MoS2 composite could be recycled and reused.

The objective of this study was to investigate the effect of decay on the electrical resistance (ER) of wood with a high moisture content (> 45%) and to try to determine the mechanism. Poplar wood blocks were exposed to a brown-rot decay fungus (Gloeophyllum trabeum (Pers. ex. Fr.) Murr.) for 2 to 12 weeks to obtain different degrees of decay. The ER values of the non decayed and decayed wood at various moisture contents were measured using a voltammetry method and were statistically analyzed. It was found that the ER of the wood blocks decreased with the fungus exposure time. Changes in the ER were quick during the first 2 weeks of exposure, which suggested that it can be used to assess early wood decay. The ER values of the decayed wood at different moisture contents were generally lower than that of the non decayed wood. A large difference (approximately 50 kΩ) was found between them when the wood moisture content was above 45%. Further analysis showed that this was because of the increase in conductive ions in the wood, rather than an increase in the moisture content. These results may be helpful to better detect the internal decay of trees using ER-based methods and could partly explain ER differences in decayed trees.