Volume 14 Issue 2

Replacement of phenol-formaldehyde with a mixed furan resin is considered in this work as a means to improving plywood properties made with urea-formaldehyde-based adhesive currently made with an addition of phenol-formaldehyde resin. Previous research showed that the furan resins can improve water resistance and can provide long stability for the glue line. Plywood was manufactured with modified adhesives and characterized in comparison with a reference product. Thickness, physical properties (moisture content, density, and total water absorption), mechanical properties (shearing strength, bending strength, and elasticity modulus in bending), and formaldehyde emission were determined according to standardized methods. The results indicated that the addition of furan resin enhanced the water resistance by 43% and formaldehyde emission is according to E1 class. Also, the mechanical properties were improved; the shear strength for the adhesive composition with furan resin was increased by 14 to 30% compared with the reference product, depending on the testing conditions.

The environmental performance was assessed for a wardrobe made from hybrid modified ammonium lignosulfonate/wood fiber composites (HWC). The HWC wardrobe system involved four subsystems, namely the raw materials supply, energy consumption, wardrobe manufacturing, and transportation. A comparative life cycle assessment of a wardrobe built from conventional medium-density fiberboard with three primary damage categories was also performed. The results suggested that the HWC composites were a more sustainable material compared with conventional boards. The raw materials supply and energy consumption influenced the three primary damage categories. Climate change on human health, particulate matter formation, fossil depletion, and human toxicity had a dominant contribution to the overall environmental impact. Also, a sensitivity analysis was performed with a focus on using wood waste as a raw material and on the different conditions for the modification of lignosulfonate for manufacturing HWC. The results indicated that the use of wood waste and an appropriate amount of unmodified lignosulfonate as a binder aids in efficient HWC production for wardrobes. These results can help to improve HWC wardrobe technology and in choosing the appropriate wardrobe system.

The oil palm tree is a monocotyledon, and the chemical composition varies relative to the part of its trunk. Therefore, the purpose of this study was to investigate the relationship between the chemical composition in different parts of an oil palm trunk and the rate of liquefaction. PEG#400/glycerol (4:1, w/w) was the liquefying reagent with 2% sulfuric acid as a catalyst. Liquefaction was done at the optimum conditions of liquor ratio, temperature (130 to 180 °C), and reaction time (30 to 120 min). The results revealed that the rate of liquefying was dependent on the part of the trunk. The inner zone in the top parts of the trunk had the least amount of lignin and lowest crystallinity. Thus, these parts could be liquefied faster than the other parts of the trunk. According to FTIR, XRD, and 13C NMR analyses, the amorphous polymer content (comprised of lignin, hemicellulose, and disordered zones of cellulose and starch) mostly degraded at the low temperature of 140 °C for 30 min, while the crystalline regions required higher temperature (180 °C). Increasing the temperature had stronger effects than extending reaction time or the liquor ratio. Furthermore, excess in these reaction parameters caused re-condensation of the degraded liquefied products.

Wood is a versatile and renewable material. It features characteristic mechanical resistance, thermal and electrical insulation, easy workability, and low energy consumption during processing. These properties make it attractive compared with other materials, mainly in the manufacturing and civil construction industries. One of the most important processes in the logging industry is sanding, though it is treated empirically by companies without a systematic study of the influence of its parameters, and it incurs high costs in this sector. Therefore, this work analyzed the effects of the sandpaper parameters (grit size and type of abrasive), wood parameters (species and fiber direction), and contribution percentage thereof on the behavior of the surface roughness and removal rate of the material. The Taguchi method was applied, and tests were performed on a flat sander with a pneumatic circuit and monitoring system for data acquisition. The tests were analyzed statistically by analysis of variance. The results showed that the surface roughness and removal rate were significantly influenced by the sandpaper parameters, but not by the wood parameters. Also, the aluminum oxide sandpaper presented greater durability and resulted in lower roughness values.

Bamboo holocellulose was oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) in water at pH 10 with an addition of 7.5 mmol g-1 of NaClO for 2 h. After oxidation, the weight recovery ratio of TEMPO-oxidized bamboo holocellulose (TOBH) was 73% with a carboxylate content of 0.65 mmol g-1. The water-insoluble TOBH was converted to an aqueous dispersion of bamboo TEMPO-oxidized cellulose nanofibrils (TOBCN) through mechanical defibrillation and centrifugation, with the nanofibrillation yield of around 90%. Transmission electron microscopy (TEM) indicated that the widths of TOBCN were estimated to be between 3 and 4 nm and lengths of several micrometers. The TOBCN dispersions had high light-transparencies of 99% at a wavelength of 600 nm. These nanofibrils were used as reinforcing nanoparticles in thermoplastic starch (TPS) films. The TOBCN dispersions were added in dosages of 0, 0.3, 0.6, 0.9, 1.2, and 1.5 wt%. Glycerol was used as a plasticizer. Nanocomposite films were prepared through a solution casting process. The TOBCN/TPS nanocomposite films exhibited high optical transparencies and their tensile strength, Young’s modulus, elongation around failure, and work to cause a fracture increased, compared to the TPS films without TOBCN. The presence of TOBCNs, at 1.5 wt%, improved moisture resistance.

Paper money passes through various environments during its life span, causing its physical, chemical, and optical properties to change. More than 90% of paper money worldwide is composed of natural cotton fiber. The present study examined the properties of paper money made of bleached softwood kraft fibers or its blends with cotton fibers, where nanofibrilled cellulose was employed as a strengthening agent. Nano-cellulose was added at 4 levels: 0, 0.3, 0.6, and 0.9%. Handsheets with a basis weight of 90 g·m-1 were made by mixing the pulp furnish with nano-cellulose in the identified percentages, and the physical and mechanical properties of the handsheets were tested. By increasing the amount of nano-cellulose up to 0.9% in cotton pulp, the tensile strength, bursting resistance, tear resistance, and resistance to folding endurance were increased by 33, 33.5, 6.6, and 63.2%, respectively, compared with the control sample. The addition of nano-cellulose up to 0.9% in cotton pulp increased the surface smoothness by up to 13.5% compared with the control sample, and porosity and water absorbance decreased by 16.6 and 4%, respectively, in comparison with the control sample. By increasing nano-cellulose up to 0.9% in cotton pulp, the opacity, brightness, and whiteness were decreased by 0.1, 1, and 4%, respectively. The SEM results indicated that the increased nano-cellulose percentage led to decreased porosity.

Manufacturing microbial cellulase in plants is an attractive strategy for the cost-effective production of cellulosic ethanol, especially the expression of thermostable cellulase, which causes no negative effects on plant growth and development. The beta-1,4-endogenous cellulase from Pyrococcus horikoshii (EGPh) is considered one of the most promising glycosyl hydrolase in the biofuel and textile industry for its hyperthermostability and its capability to hydrolyze crystalline celluloses, which has been researched extensively during recent years. In this study, the coding sequence of EGPh was expressed in Arabidopsis thaliana under the control of a CaMV35S promoter after codon optimization, with the addition of a eukaryotic Kozak sequence. The expression of EGPh caused no deleterious effects to the growth and development of transgenic A. thaliana. The heterologous EGPh showed relatively high activities, up to 111.69 and 13.35 U.mg-1 total soluble protein against soluble cellulose carboxymethyl cellulose (CMC) and insoluble microcrystalline cellulose (Avicel), respectively. The subcellular localization analysis showed that the EGPh protein was targeted to the plasma membrane and cell wall. Based on these results, it is proposed that EGPh is an ideal candidate for the commercial production of hyperthermostable endoglucanase using plants as biofactories.

The pore size distribution of cell walls in softwood pulps was studied using the pressure plate technique and mercury intrusion porosimetry, which together make it possible to cover the range from 101 to 106 nm in pore sizes (mesopores and macropores). The differences in pore size distribution between never-dried pulp from a fiber line, industrially-dried pulp, and laboratory-dried pulps were evaluated. The results showed an increase in the relative pore volume (100 to 2,000 nm) between industrial washing and bleaching stages. Also, mercury porosimetry showed a broadening of the pore size distribution of cell walls after industrial drying. Results showed that, besides the changes in micropore and mesopore size distributions, the macropore range is also affected by processing and drying.

To investigate the relationship between the chemical structural characteristics of lignin and its antibacterial activity, a low molecular weight dehydrogenation polymer (DHP) was synthesized in vitro with isoeugenol as a precursor and catalyzed by laccase. The DHP was fractionated to obtain a petroleum ether-soluble fraction (F1), diethyl ether-soluble fraction (F2), ethanol-soluble fraction (F3), and acetone-soluble fraction (F4). The results of antibacterial experiments showed that only F1 and F2 could effectively inhibit the growth of Escherichia coli and Staphylococcus aureus. Furthermore, nine compounds (Z1 to Z9) were obtained via the column chromatographic separation from F1 and F2. Mass spectrum analysis results showed that all of these compounds contained a β-5 structure. Antibacterial experiments showed that dimers (Z1 and Z2) could inhibit both S. aureus and E. coli. The trimers, tetramers, and pentamers (Z3 to Z9) could inhibit S. aureus but had no inhibitory effect on E. coli. The aldehyde groups and the condensed 5-5 structure, decreased the antibacterial properties of DHP, whereas the presence of the β-5 structure may be related to the antimicrobial ability of DHP.

Enzyme (laccase/mediator or lipase) treatment, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) surface analysis techniques were combined to explore the surface properties of Mg(OH)2-based peroxide bleached DIP (deinked pulp). The XPS survey spectra and SEM images showed that some trace elements, such as calcium, silicon, and aluminum, were present on the sample surface, in addition to the main elements, carbon and oxygen. The surface of enzyme-treated pulp was covered by the precipitated lignin or extractives. However, when the enzyme-treated pulps were bleached, the amount of precipitated lignin or extractives was considerably reduced. Lipase-treated, bleached pulp had better physical properties and lower effective residual ink concentration (ERIC) values than laccase/mediator-treated bleached pulp, which further indicated that lipase not only removed surface lignin and extractives, but it also was able to remove more residual ink contaminants.