Research Articles

Measures of the resistance to algal decay of conventional (medium density fiberboard [MDF] and plywood) and novel wood-based composites (WPC) were investigated in the same or varying wood species by using an artificial accelerated test with four mixed algal suspensions (Chlorella vulgaris, Ulothrix sp., Scenedesmus quadricauda, and Oscillatoria sp.). The morphology characterization of the surface and fracture of the specimens was analyzed using scanning electron microscopy (SEM) and a digital instrument. The pH value and the mass loss rate of the different wood species were also tested. The results showed that the algal resistance of the MDF and plywood were superior to that of the WPC of the same wood species. Furthermore, the algal resistance capacity of WPC made from various wood species were ranked as: Liquidambar formosana > Cunninghamia lanceolata and Melaleuca leucadendra > Ricinus communis > Eucalyptus grandis × E. urophylla and Pinus massoniana. There was a close relationship between the pH value and the algal resistance level; as the pH value increased, the alga resistance of the WPC also increased. The algal colonization only had a negative effect on the appearance of the samples.

This paper aimed to investigate the reasons for improved properties of bamboo alkaline peroxide mechanical pulp (APMP), such as relatively high brightness and low post-colour number, by alkali hydrogen peroxide pre-extraction (AHPP) treatment. It was found that AHPP could affect the dissolution of 1% sodium hydroxide extractives, benzene-ethanol extractives, and acid-soluble lignin. The results of Fourier transform infrared (FTIR) and 13C-nuclear magnetic resonance spectroscopy (13C-NMR) illustrated that carboxyl, syringyl, guaiacyl, acetyl, and methoxyl groups of the milled wood lignin (MWL) in bamboo were degraded slightly after AHPP treatment. However, some lignin-like structures, the links of α-O-4, β-O-4, and some carbohydrates such as xylan, α-glucose, β-glucose, α-mannose, and β-mannose in lignin-carbohydrate complexes (LCCs) were degraded noticeably. The analysis of UV spectrophotometry indicated that AHPP treatment was conductive to the degradation of some chromophores in MWL. The degradation of MWL and LCC under simulated AHPP conditions showed consistency with the above results.

Carbon fibers (CFs) were mixed with wood fibers using the solution blend method to make highly conductive fiberboards. The microstructure, conductivity, shielding effectiveness (SE), and mechanical properties of fiberboards filled with CFs of various lengths and contents were investigated. The uniform distribution of CFs formed an excellent, three-dimensional conductive network. The CF-filled fiberboards exhibited evidence of percolation and piezoresistivity. A greater content of shorter CFs was necessary to realize the effects of percolation. The corresponding thresholds of fiberboards containing CFs of 2, 5, and 10 mm in length were 1.5%, 0.75%, and 0.5%, respectively. The volume resistance of fiberboards tended to be stable as the external pressure increased to 1.4 MPa. The volume resistivity of fiberboards reached equilibrium when the CF content was 10%. The fiberboards with greater than 10% CF content exhibited a SE of 30 dB above the average, yet they met the requirements for commercial application. The mechanical properties of fiberboards were investigated, and CFs were found to enhance the modulus of rupture (MOR) and modulus of elasticity (MOE). Therefore, it was concluded that fiberboards containing CF of 5 mm in length exhibited the best performance between percolation threshold and steady CF content.

The effects of seasoning on resistance of sapwood and heartwood of Dalbergia sissoo Roxb., Acacia nilotica Wild., and Pinus wallichiana A. B. Jacks against consumption by Odontotermes obesus (Ramb.) was evaluated in no-choice and choice laboratory and field experiments. Seasoning was done in an oven at 60, 80, and 100 °C for 10 and 15 days. The amount of wood consumed generally decreased as the drying temperature increased, indicating that the drying process contributed to termites’ resistance of the woods and made them unpalatable for the termites. The woods that were dried at 100 °C for 15 days showed a significant reduction in weight after the consumption by termites compared to the woods dried at 60 and 80 °C and control both in laboratory and field trials. Similarly, the wood that was dried at 100 °C for 15 days showed highest termite mortality rate in laboratory no choice and choice tests. Consequently, the termites showed maximum feeding propensity on unseasoned P. wallichiana and the minimum on seasoned D. sissoo measured with significant differences in weight loss and mortality. Based on the feeding indicated by wood weight loss, the descending order of preference was Dalbergia sissoo > Acacia nilotica > Pinus wallichiana. The importance of wood seasoning for termites’ resistance is also discussed.

The large availability and cheap price of oil palm (Elaeis guineensis) trunk makes it an attractive raw material for value-added applications, but its low density and high carbohydrate content are highly undesirable. In this work, oil palm trunk (OPT) was steam-pretreated and compressed at high temperature. The compressed OPT was laminated using polyvinyl acetate (PVAc) using either 250 or 500 g/m2 adhesive spread rate (ASR). Soil burial testing was performed for three months on two different samples to study the deterioration and weight loss by bio-organisms. The laminated, compressed OPT formed with high PVAc ASR was found to be more durable against bio-organisms. The thermal stability of the compressed OPT was studied by thermogravimetric analysis (TGA), and it was observed that the weight loss was lower for steam-pretreated samples compared to those without steam pretreatment. Moisture absorption-desorption testing of compressed OPT was performed, and a hysteresis curve was generated. It was found that laminated, compressed OPTs with 500 g/m2 ASR had lower moisture absorption than those with 250 g/m2 ASR.

This study evaluated the possibility of producing low-density oriented strand boards (OSB) from industrial chips of Pinus sylvestris L. Statistical analysis was used to determine the lowest possible density of resulting OSBs meeting the requirements of EN standard 300 for type 3 boards. The analysis revealed that this type of board could be obtained with a density as low as 425 kg/m3, corresponding to a compression ratio of about 0.85 for pine wood. An important parameter was the quality of the pine chips, the dimensions of which should be as close as possible to the dimensions of standard wood strands.

Commercial interest in Australian hardwood plantations is increasing. The timber industry is investigating alternative supplies of forest resources, and the plantation growing industry is eager to explore alternative markets to maximize financial returns. Identifying suitable processing strategies and high-value products that suit young, plantation-grown hardwoods have proven challenging; however, recent veneer processing trials using simple veneer technology have demonstrated more acceptable recoveries of marketable products. The recovered veneers have visual qualities that are suitable for structurally-based products; however, the mechanical properties of the veneer are largely unknown. Veneers resulting from processing trials of six commercially important Australian hardwood species were used to determine key wood properties (i.e., density, dynamic modulus of elasticity (MoE), and specific MoE). The study revealed that a wide variation of properties existed between species and also within species. Simple mathematical modeling, using sigmoidal curves, was demonstrated to be an effective method to model the evolution of key wood properties across the billet radius and along the resulting veneer ribbon with benefits for tree breeders and processors.

To investigate the effect of pre-freezing treatment on the shrinkage properties and discoloration of Eucalyptus urophylla × Eucalyptus grandis wood, E. urophylla × E. grandis wood samples were treated by pre-freezing at -20 and -40 °C for 72 h and then dried to reach equilibrium moisture content at 12% and 8%, respectively. Color changes were measured by colorimeter and evaluated by diffuse reflectance visible (DRV) spectrometry; mechanical properties were also tested. The results showed that the shrinkage of Eucalyptus wood samples decreased after being pre-frozen, and the overall color change ΔE* increased by 6.11 when the treatment temperature changed from minus 20 to -40 °C. Absorption (ΔK/S) spectra in the range of 450 to 740 nm of the treatment samples exhibited flat-lined, which suggests that the color of wood stabilizes after being pre-frozen and dried. The tensile, compression and bending strengths decreased 4.74, 6.05, 1.18 after pre-freezing treatment at -40 °C, respectively. Pre-freezing treatment at -20 °C is better than that at -40 °C for improving the drying properties of E. urophylla × E. grandis wood.

Facile green synthesis of gold nanoparticles (AuNPs) on cellulose fiber was successfully achieved by reducing chloroauric acid (HAuCl4·3H2O) by means of unbleached kraft pulp. A significant color change in pulp fiber indicating the in-situ formation of gold was observed with one-step synthesis in an autoclave. As-prepared AuNP-cellulose fiber nanocomposites were thoroughly characterized by UV–Vis diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Gold nanoparticles were uniformly dispersed on the surface of the fiber by the bio-reduction of Au3+ from metal salt to Au0 with the α-carbonyl group and conjugated carbonyl of phenolic groups of lignin. The AuNPs formed on cellulose fibers were estimated to have average sizes of approximately 12.5, 12.4, 16.4, and 21.0 nm, depending on the concentration of Au3+ involved in the synthesis.

Soda-anthraquinone (soda-AQ) pulping of barley straw was used to obtain cellulosic pulps for papermaking purposes. The identified parameters, or variables to be optimized, were operating time, anthraquinone concentration, and PFI refiner revolutions, and the influence of these operating variables on pulp properties was studied. A polynomial model that reproduced the experimental results with errors less than 6% was developed. Operating variables were found (46 min of processing time, 0.4 wt.% of anthraquinone concentration, and 3000 rpm of PFI revolution) that yielded competitive pulp properties (82 °SR beating grade number, 870 mL/g of viscosity, Kappa number of 13, 77 Nm/g of tensile index, and 30% ISO brightness) at reasonable chemical and energy costs. On the other hand, this study highlights the usefulness of this polynomial model as a method to minimize the use of anthraquinone in these pulping processes and to be able to predict what the pulp properties will be. For comparison purposes, new operating conditions were found, and the pulp properties still remain at a very good level for this cereal straw.