Volume 9 Issue 2

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.

This paper discusses moso bamboo (Phyllostachys pubescens) with initial crack formation by a three-point bending (SENB) method. The corrected indentation load-displacement curve (ISO 13586-2000) and the crack opening displacement in determining the crack tip extended displacement of the specimen (ASTM E399-09) were measured using a COD gauge. Then, the load-displacement curve and the value of PQ were found by the method of 95% stiffness correction. The results showed that the bamboo has good fracture toughness, and, in this experiment, the fracture results showed little difference; the result for fracture toughness can be up to 17.39 MPa •m^1/2. By observing the crack under the microscope and the failure mode, it was found that the crack propagation was not established in accordance with the crack opening direction; rather it extended along the fiber interface.

Nypa fruticans (NF) is a lignocellulosic material belonging to the family Palmae or Arecaceae. Effects of NF content and chemical modification using methyl methacrylate (MMA) on tensile, thermal, and morphological properties of biocomposites were investigated. The results showed that the addition of NF decreased the tensile strength, elongation at break, and crystallinity, but increased the Young’s modulus, of biocomposites. Moreover, the addition of NF increased the thermal stability. Meanwhile, the tensile strength and Young’s modulus of the biocomposites treated with MMA were higher than the untreated biocomposites. The treated biocomposites exhibited higher thermal degradation temperature and crystallinity compared to the untreated biocomposites. The morphology study of the tensile-fractured surfaces of biocomposites indicated that chemical modification with MMA enhanced the interfacial interaction between NF and the PLA/rLDPE matrix.

Fractionation of softwood and hardwood LignoBoost kraft lignins, using sequential extraction with organic solvents of increasing hydrogen-bonding ability (dichloromethane, n-propanol, and methanol), was carried out. Using SEC, analytical pyrolysis, FTIR and UV/VIS spectroscopy, and chemical analytical methods, four fractions were obtained and characterized in terms of their yield, composition, functionality, lignin structural features, and antioxidant properties. In tests with free radicals (ABTS ^. +, DPPH ^. , O2 ^. -) and the ORAC (oxygen radical absorbance capacity) assay, the high radical scavenging capacity of the lignin’s soluble fractions was demonstrated. The antioxidant activity of the fractions was tested by their influence on thermo-oxidative destruction of model polyurethane elastomers. The TGA data clearly revealed the antioxidant effect of the three fractions, with the most prominent activity for the propanol-soluble fraction. The dichloromethane fraction has potential as an antioxidant for non-polar products. Novel correlations between lignin’s structural features and its radical scavenging activity were found that can be used for tuning lignin’s antioxidant properties.