Volume 15 Issue 3

This study focused on the increase of processing temperature of sugarcane bagasse fiber and polypropylene composites by removing sucrose and moisture in bagasse fibers. The relationship between the number of washing times and remaining sucrose in bagasse fiber were measured by high-performance liquid chromatography (HPLC). The analysis showed that original bagasse fibers, which had been obtained from a sugar cane mill, contained 4.0 wt% sucrose. To clarify the effect of the remaining sucrose and moisture on the limit of processing temperature in bagasse composites, the sucrose removed bagasse (40 wt%) or the original bagasse (40 wt%) was mixed with polypropylene (60 wt%), respectively. Then, the composite specimens were prepared with hot-press forming at various temperature. The observations of the composites appearances and their flexural tests were carried out. The results showed that the limit of processing temperature in the removing sucrose and moisture of bagasse composites was dramatically improved. The flexural properties in the sucrose and moisture removed bagasse composites did not decrease until 260 °C, while that in the original bagasse composites decreased at 240 °C.

Surface sizing is employed to increase the wetting resistance against liquids and to improve strength and surface properties of paper. Starch solution is the most widely used for surface sizing, and its effect is highly dependent upon how deep the starch solution penetrates into the paper structure. Better tensile strength can be obtained when starch penetrates deep into the thickness direction of paper. However, holdout of starch solution is beneficial for improving the stiffness and air or liquid resistance. This study was focused on the use of cationic polyacrylamide (PAM) as a surface sizing additive to control the penetration of starch solutions into paper, thus improving bending stiffness of paper. The effects of the ionic property, viscosity, and charge density of PAM on starch penetration and bending stiffness of surface sized papers were investigated. The penetration of starch solution was investigated with confocal laser scanning microscopy. The enthalpy changes accompanying the mixing of cationic PAMs with oxidized starch was determined using an isothermal titration calorimeter to see the molecular level interaction between PAM and starch in mixing. The addition of cationic PAM to oxidized starch solution made starch molecules stay on the paper surface rather than penetrating into the paper structure.

Wood quality depends on many circumstances, as it is sensitive to changing properties, depending on the environment. This work evaluates the influence of moisture content of selected wood-based composites on their basic mechanical properties, i.e., modulus of rupture and modulus of elasticity. The selected panels were divided by application in construction materials and furniture materials, which demand specific conditions during service-life. The increase of moisture content in different types of wood-based panels resulted in a slight reduction of the modulus of rupture and the modulus of elasticity. Boards for use in dry conditions, mainly in the furniture industry, were more sensitive to lowering their modulus of elasticity with higher board moisture content compared with those designed for humid conditions, mainly from the building industry.

This paper discusses mechanical, morphological, infrared spectral, and thermal properties of fly ash/sugarcane fiber reinforced epoxy polymer composites. Samples were prepared with and without the addition of 2 wt% of fly ash. Sugarcane fiber additions were varied from 0 wt% to 10 wt% (with an increment of 2 wt% for each sample), while the epoxy was used as a binder. A comparative study of these properties was completed on samples with and without the addition of fly ash in the composites. Based on the results obtained, the addition of 2 wt% of fly ash improved the tensile strength and hardness properties but reduced the flexural strength of the composites. Additions of fly ash reduced bubble or void formation in the composites, while toughening the composites and improving adhesion between the fiber and matrix. Samples with 4 w% of fiber and 2 wt% of fly ash composites showed high tensile strength and hardness properties, while 2 wt% of fiber composites showed high flexural strength.

Medium density fibreboard (MDF) fibres produced by a mechanical pulping process have shown potential for reinforcement in natural fibre composites (NFCs). In this work, the effect of process options, available in a pilot-scale fibre processing facility, on NFC properties were investigated. These were: a) refining energy; b) pre-treatment by sulphonation (i.e. chemi-thermo-mechanical pulping (CTMP)) and c) whether the extractives stream (i.e. the plug screw pressate) was discarded or included with the fibre. There were improvements in composite performance with refining energy, although these were not strong or consistent across composite properties. The CTMP fibres gave a substantial improvement over conventional MDF fibres in flexural, tensile, and impact properties, which may be due to improved fibre-matrix interfacial properties because of better mechanical interlocking and the removal of extractives.

A new formaldehyde-free wood adhesive, primarily composed of defatted cottonseed flour (CF) and polyamine-epichlorohydrin (K736) resin, was investigated for the preparation of interior plywood. Sodium hydroxide was an essential component of the adhesive. The effects of pH values of the CF-K736 adhesive, the CF/K736 weight ratio on the pot life of the adhesive, and the water resistance of the resulting plywood panels were investigated in detail. The hot-pressing temperature and time were optimized in terms of the water resistance of the resulting plywood panels. The resulting 5-ply plywood panels met the industrial water resistance requirements for interior application under the following conditions: pH > 11, CF/K736 weight ratio in the range of 8/1 to 5/1, hot-press temperature ≥ 120 °C, and hot-pressing time > 4 min. The pot life of the adhesive was approximately 3 h when the pH was 12 and the CF/K736 weight ratio was 8/1. The curing mechanism of the adhesive is discussed.

Experimental binderless and adhesive-bonded particleboards were made from three different sample sizes, 0 to 103 µm, 104 to 210 µm, and 211 to 500 µm from Rhizophora spp. wood trunk at 1.0 g cm-3. The objective was to evaluate the physical and mechanical properties of the particleboards. The binderless and soy-lignin bonded particleboards were fabricated and studied based on the density, internal bonding, modulus of rupture, water absorption, and thickness swelling. Microstructure study using scanning electron microscopy (SEM) and elemental analysis by carbon hydrogen nitrogen (CHN) analyser were also performed. Particleboards with adhesives improved the internal bond strength. Smaller particle sizes also were shown to be able to improve the thickness swelling outcomes, with lower hygroscopic properties. The SEM images showed that smaller particle size allowed better bonding with adhesives and provided superior strength in the fabrication of tissue equivalent phantom material. The CHN ratio demonstrated by soy flour and lignin revealed no major difference when compared with the Rhizophora spp. samples, showing basic chemical composition of natural adhesives, which was crucial in the fabrication of tissue-mimicking phantom. The study revealed the potential of soy flour and lignin as adhesives for the fabrication of Rhizophora spp. particleboard as a tissue equivalent phantom material.

Thermogravimetric analyses of Pinus sylvestris from Xinxiang were performed to investigate its kinetic characteristics, which could provide information for industrial applications. Thermal degradation experiments were conducted at various heating rates of 10 °C/min, 20 °C/min, and 60 °C/min using a thermogravimetric analysis-differential scanning calorimetry (TG-DSC) analyzer with an inert environment. The peak pyrolysis temperatures of the three major components (hemicellulose, cellulose, and lignin) were predicted by the Kissinger-Kai method, and activation energy values (Eα) were calculated. The Eα of Pinus sylvestris was also estimated by two model-free methods. The decomposition reactions of hemicellulose, cellulose, and lignin at different temperatures were the main reason for fluctuations in Eα. The time for heat transfer was less sufficient at a high heating rate compared with that at a low heating rate, which caused the temperature gradients in the samples. Therefore, the temperature of maximum exothermic peaks was higher than the maximum pyrolysis temperature. This kinetic study could be useful for providing guidance for optimizing the biomass pyrolysis process.

This paper investigated the filtration of black liquor with blade cross-flow by membrane. The lignin content in black liquid filtered by the nanofiltration membrane (NP010) is high under the transmembrane pressure of 0.5 bar, 1 bar, 1.5 bar, and 2 bar at 300 rpm and 800 rpm. In this regard, the tangential velocity on the nanofiltration membrane surface and the pressure variation on the blade in the process of filtration are simulated and analyzed with Fluent software. The tangential flow velocity on the nanofiltration membrane surface and the dynamic pressure on the blade, as well as the law of change under different rotation speed and transmembrane pressure are obtained. The comparison between experimental and simulated results have validated the numerical model of the filtration of black liquid by the blade dynamic cross-flow. According to the experimental and simulated results, the optimized filtration conditions are obtained when the blade dynamic cross-flow uses 1 kDa nanofiltration membrane to filter black liquor.

Low permeability of many wood species causes problems during timber manufacturing, including long drying times, material losses after drying, and expensive drying processes. Impregnating low permeability timber with preservatives and resins is extremely difficult. In the pulp and paper industry, use of low permeability wood results in shallow chemical penetration, and it requires the use of small-sized chips, high chemical usage, and high-energy consumption. Microwave (MW) wood modification technology can provide solutions to many of these problems. The wood structural changes in Norway spruce and radiata pine after MW modification with 0.922 and 2.45 GHz of were investigated. High intensity MW application (specific MW power 22 to 25 W/cm3, applied energy 79 to 102 kWh/m3) to moist wood caused the following wood structural changes: pit opening and pit membrane rupture; middle lamella weakening and rupture; and ray cell wall destruction and check (voids) formation mainly in the radial-longitudinal plane caused by the destruction of rays and weak middle lamella regions. Microwave destruction of different wood structure elements provided a significant increase in wood permeability for liquids and gases. Knowledge of the effects of MW treatment to the wood structure elements allows assessment of opportunities for the use of microwave irradiation in wood technology.