Research Articles

Mechanical analysis is presented for new high-strength sandwich panels made from wood-based phenolic impregnated laminated paper assembled with an interlocking tri-axial ribbed core. Four different panel configurations were tested, including panels with fiberglass fabric bonded to both outside faces with self-expanding urethane foam used to fill the ribbed core. The mechanical behaviors of the sandwich panels were strength tested via flatwise compression, edgewise compression, and third-point load bending. Panels with fiberglass exhibited significantly increased strength and apparent MOE in edgewise compression and bending, but there were no noticeable effects in flatwise compression. The foam provided improved support that resisted both rib buckling and face buckling for both compression and bending tests. Post-failure observation indicated that core buckling dominated the failures for all configurations used. It is believed that using stiffer foam or optimizing the dimension of the core might further improve the mechanical performance of wood-based sandwich panels.

Extracellular fungal cellulases are key enzymes for the degradation of lignocellulosic biomass. Greater production of these enzymes could reduce the cost of biofuels production. In this study, the basal medium for cellulase production by a Penicillium janthinellum mutant (EU2D-21) in submerged fermentation conditions was optimized using response surface methodology (RSM). Initial studies using a Plackett-Burman design (PBD) showed that (NH4)2SO4 and urea are significant factors for improving β-glucosidase and FPase production. A central composite design (CCD) was applied to obtain the maximum response, which resulted in the optimal production of β-glucosidase (5.79 IU/mL) and FPase (5.76 IU/mL). These values were 1.87 and 1.67 times higher than the corresponding values obtained under un-optimized conditions.

A microwave (MW) treatment method was applied to Chinese fir wood to improve its liquid permeability. It was found that the optimum parameters for the MW treatment of Chinese fir to achieve an improved permeability without significantly affecting its mechanical properties were as follows: a MW intensity of 20 kW, moisture content (MC) ranging from 40% to 60%, and a processing time of 60 s. The microscopic structure of Chinese fir wood before and after MW treatment was examined using a (SEM), which revealed that micro-checks were formed at the intercellular layer of ray cells and longitudinal tracheids; pit membranes were destroyed; and damage to cell walls was also observed. Mercury intrusion porosimetry (MIP) test results showed that the pore diameter at pit opening range increased after MW treatment (peak value of control sample: 553.7 nm; peak value of MW-treated sample: 921.1 nm) and micropores were generated, which also contributed to the improved permeability of Chinese fir wood. Positive correlations between microstructural changes and liquid permeability were found.

Acrylic impact modifiers (ACRs) with different soft/hard monomer ratios (mass ratios) were prepared by semi-continuous seed emulsion copolymerization using the soft monomer butyl acrylate and the hard monomer methyl methacrylate, which were used to toughen polylactide (PLA). The effect of soft/hard ACR monomer ratio on the mechanical properties of PLA/ACR blends was investigated. The results showed that the impact strength and the elongation at break of PLA/ACR blends increased with increasing soft/hard ACR monomer ratio, while the tensile and flexural strengths of PLA had little change. The impact strength of PLA/ACR blends could be increased about 4 times more than that of pure PLA when the soft/hard monomer ratio of ACR was 90/10, which was the optimal ratio for good mechanical properties of PLA. Additionally, the possible mechanism of ACR toughening in PLA was discussed through impact fracture phase morphology analysis.

The bonding interface between bamboo elements and adhesives is presumed to be significantly influenced by the degree of adhesive penetration into the porous network of interconnected cells of bamboo surfaces. In the study presented here, the average depth and effective depth of phenol-formaldehyde resin (PF) modified by different contents of lower-molecular weight (LMW) PF on bamboo surface were evaluated, making use of fluorescent microscopy characterization. The shear distribution at the bonding interface was measured by means of electronic speckle pattern interferometry (ESPI), along with tensile strength measurements, to determine the shear strain distribution on a macroscopic scale. This research combined macroscopic mechanical properties with microscopic interfacial mechanical properties, and it was found that PF modified with 10% LMW PF performed better than other modified PF. Moreover, it was assumed that the results of this study would influence the choice of bamboo-specific adhesives under different strain conditions.

Laccase is a kind of polyphenol oxidase having potential in applications for pulp bleaching, waste water treatment in mills, and removal of phenols in the food industry. The normal laccase from fungus or bacterial contains four copper atoms per protein molecular, imparting a blue color. Here it is reported that a white laccase is produced by a white rot fungus Panus conchatus from its solid-state fermentation. The activity center of this laccase is Cu2FeZn, which lacks the typical type-1 blue copper color. The polyacrylamide gel electrophoresis of purified laccase showed a main polypeptide with a molecular weight of about 60 kDa. Laccase substrate 2,6-dimethoxylphenol and others, such as syringaldazine, o-tolidine, and ABTS, were readily oxidized, among which the Km for syringaldazine was the highest. The isoelectric point of this enzyme was 3.6 and it was stable at temperatures below 45 °C over a wide range of pH (4-12).

In the furniture and construction industries, there is increased demand for lightweight, high-performance, and low-maintenance materials with specific properties. Increased demand necessitates testing of new and composite materials to find a viable alternatives to classical materials. In this study, two different types of cork layered plywood composites (plywood board with a cork core (PLYW-K1), and plywood board with a cork core and cork face layers (PLYW-K2)) were prepared and tested for their basic mechanical properties as well as screw withdrawal resistance. The measured properties were compared with standard particleboard (PB) and plywood board (PLYW1) to determine the difference in properties and potential applications. The results presented include preparation parameters, mechanical properties, maximum withdrawal force, and withdrawal resistance. In addition, the effect of screw diameter and material density on withdrawal resistance was observed. Results indicate that cork-layered plywood possessed superior mechanical properties and withdrawal strength at a much lower density than particleboard. In comparison to classical plywood, the improved factors were a reduction in density and production cost.

The preparation of nanocellulose fibers (NFs) is achieved through pretreating cellulose in a NaOH/urea/thiourea solution, and then defibrillating the fibers through ultrasonication, resulting in a high yield of 85.4%. Extensive work has been done to optimize the preparation parameters. The obtained NFs are about 30 nm in diameter with cellulose II crystal structure. They possess high thermal stability with an onset of thermal degradation at 270 °C and a maximum degradation temperature of 370 °C. Such NFs have potential applications in transistors and batteries with high thermal stability. NFs-H were obtained by homogenizing undefibrillated fibers separated from the preparation of NFs. NFs-H were also in cellulose II crystal form but with lower thermal stability due to low crystallinity. They can be applied to make highly transparent paper.

The aim of this study was to determine the antifungal and antimicrobial properties of madder root extract when used as an environmentally-friendly wood preservative and against blue stain. Plant dyestuff was extracted from the root of madder by using an ultrasonic assisted method and then applied to Turkish oriental beech, Scots pine, oak, and walnut wood blocks with the immersion (classic) and immersion + ultrasonic assisted methods. For mordants, ferrous sulfate, aluminum sulfate, copper sulfate, and vinegar were used. In order to compare the performances of the natural paints, a synthetic dye was used. The abilities of the extracts to suppress attack by brown rot (Postia placenta) and white rot (Trametes versicolor) were investigated. Treated blocks were exposed to P. placenta and T. versicolor attacks for 16 weeks according to the TS 5563-EN 113 method. Antimicrobial activity of the extracts was determined with the agar dilution method by using the disk diffusion method for bacteria. Results showed that the mordant mixes were considerably more resistant to fungal decay compared to their untreated and synthetic counterparts. In general, control (non-mordant) and vinegar mixtures showed good performance against brown and white rot fungi. Copper mixes showed better antimicrobial activity against all types of microorganisms. In conclusion, it was found that madder root extracts and mordant mixes could be used as wood preservatives.

Enzymatic hydrolysis of rapeseed meal carbohydrates was performed to increase the protein content. Rapeseed meal was first screened and further defatted. Only particles between 0.250 and 0.707 mm in size were used, and the optimum solid/liquid ratio was found to be 10% (w/v). Commercially available carbohydrase enzyme mixtures, Viscozyme® L, Pectinex® Ultra SP-L, and Celluclast® 1.5 L, were used in conditions that minimized protein solubilization from the solid phase. The highest results were achieved with Viscozyme® L, with a carbohydrate extraction yield of 80% (as determined by reducing sugars content expressed as glucose equivalent units) after 24 h of reaction at 45 ºC, pH 3.5, and an enzyme dosage equivalent to 96 fungal beta-glucanase (FBG) added to 5 g of defatted rapeseed meal. The simultaneous use of the different carbohydrases (Viscozyme®, Pectinex®, and Celluclast®) did not improve the carbohydrate hydrolysis when compared to the use of Viscozyme® L alone. Viscozyme® L treatment increased the protein content in the rapeseed meal from 41 to 68%, which allowed the solid to be classified as a protein concentrate.