Volume 9 Issue 4

A safety analysis for Larch (Larix gmelinii) 2×4 lumber, based on the requirements of Chinese national standards, is presented in this paper. Static, third-point bending tests were conducted using an MTS universal testing machine. The bending strength was adjusted to 15% moisture content (MOR15) and was fitted with three different probability distribution models. The best fitting MOR15 model for Larch 2×4 lumber possessed lognormal distribution. Furthermore, a procedure for calculation of a reliability index (β) was developed using the first-order second-moment method. Results of reliability analysis indicated that the reliability indexdecreased nonlinearly as both the design value of bending strength increased and the reduction of live to dead load ratio (ρ). Finally, it was suggested that the design values for the bending strength of Larch 2×4 lumber were 18.4 MPa for grade SS, 11.6 MPa for grade No.1, 12.7 MPa for grade No.2, and 10.3 MPa for grade No.3, to meet the target reliability level.

Poly-(vinylidene fluoride) (PVDF), which has a low surface energy, is a common material used for ultrafiltration (UF) membranes. Bacterial cellulose (BC) contains a large number of hydroxyl groups, which has a strong water holding capacity. It can improve the hydrophilicity of PVDF. By means of in-situ composite preparation, with the introduction of tetraethoxysilane (TEOS) as silicon source from the outside of BC and polymerizing, hybrid reinforcing material comprised of BC and silica (BC/SiO2) was achieved which were catalyzed by different acids. After that, by means of a phase separation method with PVDF, composite membranes (PVDF/BC/SiO2) were prepared. Visible spectrophotometry, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to investigate the characteristic of BC/SiO2 hybrids. The structure and properties of composite membranes were also investigated. After catalysis by acid, SiO2 particles uniformly adhered to the surface of BC fibers, which resulted in small pores being formed preferentially in the interface of PVDF composite membranes, while reducing the finger-like pores. At the same time the retention of the composite membranes were improved. So both the properties and structure were improved due to the presence of certain BC/SiO2 hybrid reinforcements.

An efficient wood harvesting activity aims to fully recover wood as a measure to increase the profit, but safety prescriptions should be obeyed each time when harvesting operations are performed. A study was carried out in three forest compartments in order to determine whether the actual tree felling procedures match the recommended ones and, if not, to compare how the used practices may affect the wood recovery when felling trees using a conventional undercut. The study yielded significant statistical differences between the recommended and used cuts dimensions, as well as significant differences between the procedures used by three studied work teams. The general trend was to make deeper cuts and smaller openness when performing undercuts. Since one reason for such tree felling procedures may be the increment of wood recovery rate, we conducted a comparative analysis between the potential volume loss in the two mentioned scenarios, and only small differences were found; this should discourage the use of such tree felling techniques. The present estimates suggest that the potential volume loss was 0.89 to 1.20% of the harvested volume, yielding small gains in terms of wood recovery if compared to that of 1.74 to 3.17% corresponding to the recommended practices.

Cotton stalk bark fibers (CSBF) were extracted by steam flash explosion, completed within 0.09 s, and the extracted fibers were compared with those obtained by conventional alkaline treatment. Results indicate that the optimum steam pressure was 2.5 MPa when steaming time was set to 2 min for extracting CSBF. Under the optimized conditions, the obtained CSBF had a cellulose content of 72%, length of 48 mm, fineness of 45 dtex, crystallinity index of 68, moisture regain of 8%, water retention of 98%, and tensile strength of 2.4 cN/dtex, which were similar to results obtained by conventional alkaline treatment. Compared with bark of cotton stalks, CSBF had lower moisture regain and water retention, and higher onset decomposition temperature. The results show that moderate steam flash explosion is a chemical-free, quick, and effective method for exploring the industrial applications of bark of cotton stalks as natural cellulose fibers.

Information on the morphological and physical properties of biofibers is necessary to support the mechanical understanding of the biological design of plants, as well as for the development of new technology that adds value to non-traditional bioresources, such as those based on Ulex europaeus fibers. Ulex europaeus fibers were extracted through a chemical pulping process at 170 °C and with 40 g/L NaOH. The dimensions of the fibers produced were 0.97 ± 0.1 mm in length and 13 ± 2 μm in diameter. Pressed fiber paper sheets were made to evaluate their mechanical properties. Burst and tear indices of 1.2 mN/kg and 8.6 Nm²/kg, respectively, were recorded. The values obtained did not compare well to fiber paper sheets from Pinus radiata, presumably due to the significant amount of non-structural elements of wood present in the samples and the lower length of Ulex europaeus fibers, which resulted in lower tensile strength. Additionally, nanoindentation tests were conducted to assess the hardness and elastic modulus of the fibers, obtaining average values of 0.84 GPa and 9.23 GPa for the stem, respectively. These values were significantly lower than those of industrial biofiber, perhaps due to the lower morphogenic maturity of Ulex europaeus fibers compared to other traditional sources of fiber.

The aims of this study were response surface modeling and optimization of Cr(VI) removal from solution using formaldehyde-modified eucalyptus bark. A high removal rate of Cr(VI) was achieved under the conditions of low adsorbent dosing quantity and high initial concentration of Cr(VI). Analysis of variance showed a high multiple coefficient of determination (R2=0.9875), adjusted determination coefficient (R2Adj=0.9714), and the good second order regression equation. The initial concentration of Cr(VI) was 40.15 mg/L, adsorbent dosing quantity 3.40 g/L, and initial reaction pH 2.78, and the largest removal rate was 99.998% under the optimum reaction conditions. Langmuir and Freundlich isothermal models described well adsorption of Cr(VI) by the modified stringy bark. Adsorption kinetics studies showed that the adsorption was controlled by multiple factors, dominated by chemical adsorption. The adsorption was found to be spontaneous and endothermic, with △G0 < 0, △H0 > 0, and △S0 > 0. Adsorption of Cr(VI) by formaldehyde-modified stringy bark was partly controlled by REDOX reactions. The adsorbents were characterized by SEM and FTIR.

Cellulose adsorbent was prepared by ATRP grafting of glycidyl methacrylate onto a cellulose backbone with subsequent functionalization with ethanediamine, and then used for the removal of Cr(VI) from aqueous solution. Batch experiments were carried out to investigate the effects of initial pH and initial Cr(VI) concentration on the adsorption performance. The optimum pH for adsorption of Cr(VI) ranged from 2 to 3, and the maximum uptake of Cr(VI) from solution was 500 mg/g at pH 3.0 and 50 °C. Langmuir and Freundlich isotherms were applied to the adsorption process, and the thermodynamic parameters were calculated. The results showed that the sorption process to be feasible, spontaneous, and endothermic. Kinetics studies revealed that the pseudo-second-order kinetic model fitted well with the experimental data and the intra-particle diffusion was not the only rate-determining step for Cr(VI)sorption onto adsorbent. The cellulose adsorbent before and after Cr(VI) adsorption were characterized using scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Regeneration of cellulose adsorbent loaded with Cr(VI) can be achieved by treating with 2.0M NaOH.

An experimental study of wood impregnation was implemented by applying centrifugal methods. The impregnants were a 10% aqueous solution of potassium chloride and a 2% aqueous solution of borax. Birch (Betula pendula) and aspen (Populus tremula) wood samples in different moisture content were tested. The impregnation time in the centrifugal device were 30 seconds repeated 21 times, and the samples were measured after every 30 seconds. The experimental results were fitted to a nonlinear filtration law, which indicated that the centrifugal wood impregnation was dependent on wood species, wood moisture, rotational speed, and radius. Determination of rotational speed and centrifuge radius for impregnating aspen and birch at varying lengths and humidity under conditions of the nonlinear impregnant filtration law can be done using the example charts that were developed and presented in this study.

Producing microbial oils via oleaginous yeast fermentation has drawn broad attention in the biodiesel industry. The oleaginous yeast Lipomycesstarkeyi utilizing diverse carbon sources including glucose, xylose, glycerol, and willow wood sawdust (WWS) hydrolysate for the biosynthesis of oils in its cell growth were investigated in this study. High carbon/nitrogen ratios within the glucose media significantly increased the lipid content of Lipomycesstarkeyi cells and modified the fatty acid composition of lipids, promoting the accumulation of C16:0 fatty acids and saturated fatty acids (C16:0 and C18:0). The accumulation of C18 fatty acids (C18:0, C18:1, and C18:2) and unsaturated fatty acids (C16:1, C18:1, and C18:2) was restricted. When crude glycerol and WWS hydrolysate were used as the sole carbon sources for L. starkeyi fermentation, the dry cell weight, lipid content, and lipid productivity were 9.1 g/L, 46.2%, and 4.2 g/L, respectively, for glycerol, and 8.2 g/L, 42.7%, and 3.5 g/L, respectively, for the hydrolysate solution. This study provides useful information for producing oils with L. starkeyi fermentation using glycerol and WWS hydrolysate as the primary or secondary carbon substrates.

The surface of oil palm empty fruit bunch fibres contains embedded silica bodies or protrusions. The mechanical contribution of the protrusions towards the integrity of the fibres is still not clearly investigated. In this work, 2D and 3D finite element simulations on the surface and cross section of the fibres, respectively, were performed. The information for the models was obtained from scanning electron microscopy analysis and mechanical tests for the silica body characteristics and elastic modulus, respectively. Different silica bodies arrangements and the effect of spiked geometry of the silica bodies was investigated using 2D models. Cohesive zone modelling was introduced to simulate damage or debonding between the interface of silica bodies and fibre. A 3D finite element model was later developed consisting of a silica body (sphere) embedded halfway in the matrix. The numerical results showed that the 2D model was sensitive to critical stress compared to silica bodies spiked geometry, arrangement of silica bodies on the fibre surface, and cohesive energy. On the other hand, the results showed that for 3D models with thicknesses larger than 0.2 mm, the effect of the silica bodies on the elasticity of the fibre was not significant.