Volume 14 Issue 4

Cellulose transparent and flexible film was prepared by dissolving micro-crystalline cellulose powder in Dimethylacetamide/Lithium Chloride (DMAc/LiCl) followed by regeneration in acetone and subsequent washing with water. The solution was cast on a glass plate. The interactions of water molecules and the swollen cellulose in the gel were examined by differential scanning calorimetry, DSC. An increased melting point of water in the gel indicated the presence of stronger bonding between water and cellulose than in the non-modified cellulose. The prepared dried films had 63 g/m2 weight and 0.06 mm thickness with 1.14 g/cm3 density.The prepared dry film exhibited high transparency, around 95% with visible light. The transparency and mechanical properties of the films were stable at high temperature (120°C) and exposure to UV irradiation. Thermal analysis of the prepared sample indicated film stability up to 275 °C. The tensile strength of the cellulose film was around 120 MPa with about 10% strain to break. The mechanical properties of the films were stable in alkali and acidic solutions.

Different transition metals (Ni, Co, Fe, and Mn) at different amounts (0 mmol/g to 1 mmol/g) were introduced into the co-pyrolysis of rice straw and polyethylene. The thermal behavior and the kinetics of rice straw, polyethylene, transition metal-treated rice straw, rice straw/polyethylene, and transition metal-treated rice straw/polyethylene were comparatively investigated via thermogravimetric analysis. The Ni, Co, Fe, and Mn promoted the decomposition of rice straw and polyethylene in mixtures compared with non-transition metal-treated mixtures in terms of the initial decomposition temperature. The presence of these transition metals catalyzed the synergistic interaction between the rice straw and the polyethylene in mixtures, which resulted in a reduction of residue yield from 14.9 wt% for rice straw/polyethylene to 12.6 wt% to 14.5 wt% for transition metal-treated mixtures. Moreover, the difference in weight loss suggested that the negative influence of the softened polyethylene on the rice straw in mixtures could be greatly reduced after the involvement of transition metals. Kinetic analysis revealed that the pyrolysis of rice straw, polyethylene, and transition metal-treated rice straw were well fit by a single first order reaction; two consecutive first order reactions were needed to describe the co-pyrolysis of rice straw/polyethylene with or without transition metals.

Enhanced cellulase production was studied with ultraviolet mutagenesis and the mutated cellulase gene in E. coli DH5α was cloned for production under controlled conditions. Aspergillus niger inoculum was exposed to UV radiation for different time intervals. The UV exposure of 10 min to A. niger yielded 330 μmol/min/mg specific activity. The mRNA of mutant A. niger yielding maximum enzyme activity was isolated and used for the synthesis of cDNA. The cDNA prepared from mRNA was used for the PCR amplification of mutated cellulase gene with primers designed on the basis of a cellulase gene database from A. niger. The amplified cellulase gene was cloned into E. coli DH5α followed by expression in E. coli BL21. The cellulase activity by wild type A. niger, A. niger UVMT-I, and recombinant E. coli was compared by analysis of variance test. The specific activity of cellulase by recombinant E. coli was maximum (441 μmol/min/mg), followed by A. niger UVMT-I (330 μmol/min/mg) and wild type A. niger (96 μmol/min/mg).

Rotary veneers from spotted gum (Corymbia citriodora) and white cypress pine logs (Callitris glaucophylla) recovered from the native forest in Queensland, as well as Queensland plantation hoop pine (Araucaria cunninghamii) logs were used to manufacture LVL products following six different lay-up strategies including blended species LVL. The different lay-up strategies were to determine the opportunities for improving the mechanical performance of plantation softwood LVL by including native forest veneers. The manufactured products were evaluated for their bending performance, tension, bearing strength perpendicular to the grain, and longitudinal-tangential shear strength. The all-spotted gum LVL showed superior performance in all testing compared to other construction strategies. Blending even a small amount of spotted gum veneer with plantation hoop pine veneer resulted in improved mechanical performance, especially in flatwise bending. Opportunities exist to develop more optimised construction strategies that target specific product performances while optimising the use of the variable veneer qualities generated from log processing.

Structural development and modification of bamboo culm’s anatomical characteristics occur during the maturation period. This process affects the conductivity efficiency in individual bamboo culms (above ground). The present study clarified this process in the sympodial type of bamboo rhizome (belowground). This study aimed to observe the anatomical characteristics of Gigantochloa scortechinii rhizome, examine their relationship with different study sites and rhizome ages, and investigate their relationship with hydraulic conductance. Destructive sampling on four consecutive rhizomes was conducted using a selective random sampling method. All rhizome anatomical characteristics were significantly different between study sites except parenchyma diameter, parenchyma lumen diameter, and fiber cell wall thickness. The results also indicated that the vascular bundle diameter, parenchyma diameter, parenchyma lumen diameter, parenchyma cell wall thickness, fiber diameter, fiber cell wall thickness, and fiber length increased with age, but radial to tangential ratio decreased with age. All measured characteristics including the conductance elements had no relationship with hydraulic conductance, except parenchyma diameter and parenchyma lumen diameter. The sizes parenchyma diameter and lumen diameter did not imply a determinant factor in hydraulic conductance. Further studies on rhizome chemical attributes should be carried out to isolate the cause of decreasing hydraulic conductance.

In order to simultaneously improve the strength and decoration properties of plantation wood, a multi-effect modifier was prepared by compounding acid red 18050(G) with melamine-modified urea formaldehyde resin (MUF). Various compounding methods for MUF synthesis such as adding dye with the first part urea (U1G) or with the second part urea (U2G), or direct blending with MUF resin (BG) were tested. Chinese fir plantation wood was impregnated with these modifiers separately, and its color, color fastness, and dyeing mechanism were studied. The results showed that G had good compatibility with MUF and could prolong its storage time, and all compound modifiers exhibited permeability and coloring effect on Chinese fir wood. Compared with G-dyed wood under the same conditions, all the compound dyed wood had better color fastness to water, and the U2G-dyed was the best, the color fastness to xenon light of U2G dyed wood was greatly improved.. Fourier transform infra-red (FTIR) analysis showed that compared with MUF-modified wood, the dye affected MUF hydroxyl-methylation reaction in U1G, lowered the polycondensation degree, and extended its storage time. The dye might have promoted the ionic reaction between resin amino and dye sulfonic groups in U2G, thus displaying better color fastness.

The feasibility of performing finger jointing of green rubberwood was considered with typical adhesives used for gluing kiln-dried wood. The effect of initial moisture content of rubberwood (12 ± 1.1%, 37.6 ± 3.2%, and 61.2 ± 6.1%), hot air oven-drying temperatures (60 °C, 80 °C, and 100 °C), and types of adhesives (polyurethane (PU) and emulsion polymeric isocyanate (EPI)) on bending and compressive properties of finger jointed rubberwood products were investigated. The controls were manufactured from 12 ± 1.1% moisture content rubberwood. The type of adhesives had no significant effect on the examined properties of the finger-jointed specimens. The initial moisture content had a slight effect on the modulus of rupture (MOR) and modulus of elasticity (MOE) of specimens bonded with EPI adhesive. The MOR of all types of specimens bonded with EPI adhesive were slightly lower, but their MOE tended to be slightly higher than the control. The drying temperature slightly improved the MOE of specimens bonded with EPI adhesive. The result suggests that the finger jointing process of green rubberwood using typical adhesives could be performed without notably reducing the strength of the final products compared with the control.

The main objective of this study was to investigate the key mechanical properties of cross-banded laminated veneer lumbers (LVL-C) manufactured from blending veneers recovered from sub-optimal native forest spotted gum and plantation hoop pine logs. The recovered veneers were separated into three grades based on their dynamic modulus of elasticity (MOE). Additionally, the spotted gum veneers were visually graded to evaluate whether a relationship exists between the MOE-based and visual grades. In total, six 12-ply reference LVL and six mixed-species 12-ply LVL-C panels were manufactured and analyzed for (i) flatwise and edgewise bending performance; (ii) bearing and tension strength perpendicular to the grain; and (iii) longitudinal-tangential shear strength. Little correlation was found between MOE-based and visual grades for the spotted gum veneers. The LVL- C showed flatwise and edgewise MOE up to 24% and 13% lower, respectively, than the reference mixed-species LVL. The flatwise and edgewise modulus of rupture were up to 39% and 19% lower, respectively. On average, the tensile and bearing strengths of the LVL-C were considerably higher than the hoop pine LVL and mixed-species LVL, with the former being approximately three times higher. The manufactured LVL-C showed markedly higher bending properties and tensile strengths than commercial LVL-C products.

Bamboo floorings are the most important industrial products in the bamboo sector. With the aim of providing a useful guide for the development of bamboo floorings, this study quantitatively assessed the environmental impacts of the two primary types of bamboo floorings, laminated flooring and scrimber flooring, using life cycle assessment (LCA) software SimaPro. The purpose of this study was to find out which type of bamboo flooring is more environmentally friendly through quantitatively analyzing the input and output of materials and energy during the whole life cycle of the two types of flooring products. The present study demonstrated that the majority of the environmental burdens were associated with the process of bamboo strip production for bamboo laminated flooring (59.3%), and the process of panel processing for bamboo scrimber floorings (56.9%). In terms of environmental loads, bamboo laminated flooring was considered more sustainable than bamboo scrimber flooring, as the total environmental loads of bamboo scrimber flooring was approximately 1.6 times that of bamboo laminated flooring.

Tungsten trioxide (WO3) nanosheets were deposited onto a wood surface by a solvothermal synthesis method using temperatures between 90 and 120 °C. These WO3 nanosheets were used to improve the color, as well as to enhance the photochromic characteristics and ultraviolet aging resistance of the wood. The results indicate that the WO3 nanosheets on the wood’s surface were affected by the treatment temperature. The formed nanosheets included nanoparticles and rod-shaped structures, which are highly crystallized. Different structures were generated in the nanosheets, which affected their functionality. The modified wood not only exhibited photochromic phenomena when excited by ultraviolet radiation, but also demonstrated resistance against ultraviolet light aging.