Research Articles

A three-component flame-retardant system was prepared based on in situ polymerization of ammonium polyphosphate (APP), diatomite (DE), and aluminium trihydroxide (ATH) to improve the flame retardance and smoke suppression properties of fibrous materials. Compared to the two-component system of APP-DE, the addition of APP-10% DE-4% ATH dosed at a filler load of 20% of the fibrous material reached a limited oxygen index of 27.5%, which was approximately 9.1% higher than the two-component system. The lower mass loss rate and higher residual mass at high temperatures resulted in excellent flame retardance. The synergistic effect on alleviating combustion and reducing heat release was shown by the 16.6%, 22.1%, and 12.5% decreases in the peak heat release rate, total heat release, and average effective heat combustion, respectively. Superior fire resistance was demonstrated by a higher fire performance index and a lower mass loss. A smoke suppression effect was shown by the peak smoke release rate and the total smoke release results that were 28.7% and 15.8% lower than the two-component system, respectively. Based on the porous structure of DE and generated aluminum oxide (Al2O3), the outstanding adsorption effect and flame-retardant effect was also demonstrated by the production rate of carbon monoxide (CO) and carbon dioxide (CO2).

Four additives including two specimens of kaolin clay, limestone, and a byproduct of a sugar mill (BSM) (mainly CaCO3) were utilized to increase ash fusion temperature (AFT) of corn straw. The results showed that the ash softening temperature (ST) was increased by 250 to 380 °C and agglomeration or slagging could be avoided during combustion with each additive. Meanwhile, the slagging/fouling tendency of all ash samples fell within the “low” range according to alkali index. Lime was shown to have the best effect, which indicated that calcium oxide was the best compound to increase the AFT of corn straw densification (CSDF). Both kaolin specimens made the fusion range very narrow. BSM had the least effect on ST among the four. All the additives diluted the concentration of chlorine by more than 50%. No agglomeration or slagging phenomenon appeared in real boilers burning CSDF with lime blended as additive.

Recently, enhancing the performance of polyurethane (PU) coatings with cellulose nanomaterials (CNM) has been actively researched. Cellulose nanomaterials exhibit considerable potential to increase the mechanical strength of PU coatings due to their high aspect ratios and elastic moduli. In this study, PU reinforced with CNM was coated onto paper to enhance the paper’s mechanical strength and soiling resistance. To investigate the reinforcing effect, two different CNM, cellulose nanocrystals (CNC) and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibers (TOCN), were selected, and suspensions with different ratios of PU and CNM were prepared. After coating the paper with each of them, the mechanical properties of the paper, including tensile strength, folding endurance, and soiling resistance, were evaluated. The mechanical strength and anti-soiling performance of the PU-CNM coated papers were greatly enhanced. Especially, PU-TOCN had superior properties as a durable paper coating despite a low TOCN concentration, less than 2%, because the TOCN crosslinked with PU via polyaziridine. Furthermore, the PU-CNM coating protected the paper from being contaminated, which was confirmed by scanning electron microscopy and energy dispersive X-ray mapping. Consequently, durable paper exhibiting soiling resistance was fabricated by coating the paper with PU-TOCN suspensions.

The effect of the end distance was studied relative to the static ultimate lateral load capacity of a single-shear unconstrained wood-plastic-composite-to-metal single-bolt connection (SUWSC). Equations estimated the static ultimate lateral loads of the SUWSCs that failed during the end tear-out, splitting, and yield modes and were obtained using stress concentration factor regression- and mechanics-based approaches. The experimental results showed that the stress concentration factor was a linear function of the end-distance to bolt-diameter ratio for the SUWSCs that failed during end tear-out and splitting modes. The static ultimate lateral loads of the SUWSCs that failed during the yield modes were estimated using a mechanics-based equation. The minimum end distance for the SUWSCs that failed without end fracture (i.e., only with yield mode) was 25.4 mm, which was four times larger than the bolt diameter.

Epoxidized jatropha oil (EJO) was investigated as a sustainable alternative to petrochemical-based plasticizers to reinforce the plastics, leading to increased ductility and toughness of kenaf-reinforced poly(lactic acid) (PLA). The EJO was melt-blended into kenaf-reinforced PLA at concentrations from 1 wt% to 5 wt%. The blends were then hot-pressed into sheets to characterize their mechanical and physical properties. Kenaf fibers were treated with 6% sodium hydroxide (NaOH), and the effects thereof on the composites’ tensile, flexural, and impact properties, as well as their water absorption and density were stu died. The impact strengths of the kenaf-reinforced PLA composites were improved with the addition of EJO up to 5 wt%, with a maximum over 10 times that of the neat PLA. The flexural strength and modulus increased 4% and 50%, respectively, for treated kenaf-reinforced PLA plasticized with EJO. This increase demonstrated the alkalization treatment’s notable improvements to the composites’ properties. Furthermore, analysis by scanning electron microscopy (SEM) of the composites’ tensile fracture surfaces indicated better interaction adhesion of the treated kenaf-reinforced PLA plasticized with EJO compared with the untreated composites. Compared to untreated 1 wt% EJO biocomposites, the treated 5 wt% EJO biocomposites reduced water absorption from 3.1% to 1.6% after 8 weeks of immersion.

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.