Volume 10 Issue 3

Ultrasound was applied to enhance mass transfer within the boundary layer during wood vacuum drying. Fast growing poplar (Populus tomentosa) was used as the specimen in this work. The water migration rates and the mass transfer coefficients were studied at temperatures of 35 and 50 °C, absolute pressures of 0.03, 0.06, and 0.1 MPa, and ultrasound power-frequency groups of 60 W-28 kHz, 100 W-28 kHz, and 100 W-20 kHz, respectively. The results indicated that ultrasound could markedly increase the water migration rates within the boundary layer. The water migration rates increased with increasing ultrasound power and frequency. The mass transfer coefficients within the boundary layer for specimens treated with ultrasound were much higher than those of the control group, and the mass transfer coefficients increased with decreasing absolute pressure. Ultrasound could be applied in the wood drying industry as a means of saving time and energy.

The objective of this study was to determine rheological behaviors of maple veneer plastic composite (MVPC) prepared by full cell preparation technology through the use of a rotational rheometer. The results showed that at 25 to 105 °C, the storage modulus G‘ and loss modulus G” of the MVPC were apparently higher than that of the control. In the range 105 to 210 °C, the storage modulus G‘ of the MVPC was basically the same as that of the control, and the loss modulus G” was slightly higher than that of the control. At 105 °C, the Tanδ curve of the MVPC had an obvious peak, which indicated that the glass transition temperature (Tg) of the MVPC was about 105 °C. The rheological behavior of the MVPC with different impregnation weight gain rates showed that the MVPC with a 55% impregnation weight gain rate had higher G‘, G”, and Tanδ.

Laccase, an enzyme capable of degrading lignin, has become an effective agent for green processing and has great significance for the protection of the environment and the development of a low-carbon economy. In this work, wood fibers were selected as the raw material, and with activation by a laccase-mediator system, lignin was changed to a natural adhesive material, and the high temperature/high pressure method was used to prepare medium density fiberboard (MDF). The bonding mechanism was explored with measurements of Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), environmental scanning electron microscope (ESEM), and X-ray diffraction (XRD). It was found that the self-adhesive effect was realized through esterification, hydrogen bonding, polycondensation, coupling, and a Schiff base reaction, among which coupling and polycondensation were the primary reactions. The chemical bonds between the MDF interior and surface varied because of the mobility of the lignin during the reaction.

Bleached bamboo fiber was treated with a high pressure enzymatic hydrolysis (HPEH) process in order to produce microfibrillated bamboo fiber (MBF). Mixture design of experiments was utilized to determine the optimal constituents of fiber, enzymes, and water for the HPEH process on the isolation yield of the MBF. Results showed the optimal combination for the maximal yield isolation of the MBF was 1 g fiber, 1 g enzyme, and 1 L water at 90 MPa and 70 °C. The influence of the reaction time of the HPEH process (6 to 48 h) was also evaluated in this study. Morphological and thermal property analyses of untreated and treated bamboo fibers revealed that the HPEH process was effective for removing non-cellulosic components from the fibers. Thus, the HPEH process is an effective method for the isolation of the MBF, with the benefits of elevated crystallinity and thermal stability.

This study investigated changes in the physical properties of oil palm (Elaeis guineensis) wood (OPW) using various buffered media for the hydrothermal treatment process. The buffered media were prepared separately for three different treatment conditions: pH of 8, pH of 5, and tap water. These treatments were compared with unbuffered, control samples. The OPW samples were taken from the outer part of the trees. The OPW samples were treated with the buffered media at a temperature of 140 °C for 120 min. The parameters evaluated were wood density (ρ), equilibrium moisture content (EMC), mass loss (ML), water absorption (WA), volumetric swelling (SV), anti-swelling efficiency (ASE), and water repellent efficiency (WRE), for both treated and untreated samples. The buffered media significantly affected the EMC (%), ρ (g/cm3), ML (%), and WA (%), with no significant effects on the ASE (%) and WRE (%). It was concluded that the hydrothermal treatment in the buffered medium with a pH of 8 had the most significant effect on the physical properties of OPW.

The natural durability of wood to mold fungi was tested under laboratory conditions with locally sourced Citharexylum spinosum and Morus alba woods. The mold fungi were Penicillium selerotigenum, Paecilomyces variotii, and Aspergillus niger. Changes in surface elemental composition were evaluated with energy dispersive X-ray spectroscopy (EDX) and the biodeterioration of wood surfaces by scanning electron microscope (SEM). The C peak element of C. spinosum wood was affected significantly (P = 0.0004) and decreased from 49.91% in the control specimens to 47%, 40.1%, and 40% with P. selerotigenum, A. niger,and P. variotii,respectively.Also, the C peak element of M. alba heartwoodsignificantly decreased (P < 0.0001) from 51.33% in the control specimens to 41.49%, 45.66%, and 43.66% in wood inoculated with A. niger, P. variotii,and P. selerotigenum,respectively. The elements Al and Cu were observed in high percentages with M. alba heartwoodinoculated by P. variotii. The methanol extract from M. alba heartwood showed good inhibition against the growth of A. niger at a concentration of 32 μg/mL, and the methanol extract from C. spinosum woodshowed remarkable inhibition against the growth of P. variotii at a concentration of 8 μg/mL. The results of this study clearly showed the changes that occur in wood samples as a result of fungal infestation.

The use of cellulose nanofibers (CNF) as an additive in papermaking is an attractive alternative to improve paper’s strength. However, the costs of CNF production need to be competitive compared to other approaches aimed at reducing mechanical beating. Five different types of CNFs were prepared following different pretreatments: TEMPO-mediated oxidation at basic and neutral conditions, soft acid hydrolysis, enzymatic treatment, and mechanical beating. All of the pretreated fibers were later passed through a high-pressure homogenizer. The resulting CNFs were each applied to a papermaking pulp to investigate their reinforcing ability. Results indicated that the TEMPO-oxidized CNFs offered the highest increase at the same nanofiber content compared to the other types of CNFs. However, an analysis of the cost of increasing paper’s breaking length by 75% indicated that TEMPO-oxidized CNFs were more expensive than the other CNF grades, whereas CNFs from mechanical and acid pre-treatment offered similar increases at lower prices. The results indicated that CNFs of high fibrillation degree were not necessary to induce dramatic increases in paper strength. This finding offers a new possibility for the escalation of CNF production to industrial levels with competitive prices.

Utilizing wood powder and corn starch as the main materials with polyurethane adhesive as a cross-linking agent, the starch/wood powder composite material was prepared via molding forming techniques. The effects of wood powder mesh and addition of wood powder on the properties of composite material were investigated. The compatibility of starch and wood powder and the thermal stability of composite were evaluated by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMA), respectively. The mechanical properties and water absorption of composite material were also tested. The results showed that the mechanical properties and water resistance of composite material first increased and then fell with increasing mesh, and the best performance was obtained when the mesh ranged from 80 to 100. The best compatibility, mechanical properties, water resistance, and thermal stability of composite material was obtained with 10% polyurethane crosslinking agent addition.

A 100% renewable, easily-prepared, and industrialized abrasive grinding wheel was produced based on a biobased thermosetting resins matrix; the matrix was made of condensed tannin-furanic resin, originating from biosourced raw materials such as tree barks and crops, which bond the particles of glass sand. These grinding wheels exhibited no cracks or pores. Moreover, the related properties of these products were characterized by the measurements of compression resistance, Brinell hardness, and wear resistance; the results were comparable to those of commercial grinding wheels prepared with synthetic phenolic resins and aluminum oxide particles. The results indicated that incomparable hardness and strong resistance towards compression can be obtained using the new tannin-based grinding wheels. Besides that, the results also revealed excellent properties of abrasiveness when compared to a commercial Taber Calibrade wheel H-18.

A new computational model, based on fracture mechanics, was used to determine cutting forces. Unlike traditional computing methods, which depend on many coefficients reflecting the machining of solid wood, the new model uses two main parameters: fracture toughness and shear yield stresses. The aim of this study was to apply this new method to determine these parameters for the tooth cutting edge principal positions and longitudinal and perpendicular cutting speed directions. Samples of beech wood (Fagus sylvatica L.) were sawn. The measurements of energetic effects (cutting power and cutting force) while sawing wood were carried out on two laboratory stands: the sash gang saw and the circular sawing machine. The basic relationships between different sawing methods, such as cutting on a frame sawing machine (sash gang saw) and a circular sawing machine, and the fracture toughness and shear yield stresses were recognizable. The data obtained could be applied to the computation of the energetic effects on other wood cutting methods.