Research Articles

Short date palm tree lignocellulosic fibers were used as a reinforcing phase in a polyepoxy thermoset commodity resin. Unmodified fibers as well as counterparts chemically oxidized using TEMPO catalyst mediation were used as fillers for composite materials prepared in a Resin Transfer Molding process. The preparation was facilitated in the case of the composites based on oxidized fibers. During the process, the front displacement of injected resin was more regular, more homogeneous, and faster in the case of oxidized fibers. The morphology, thermal and mechanical properties of the resultant composites were characterized by SEM, DSC, DMA, as well as three-point bending and Charpy impact tests. An elevated reinforcing capability of the oxidized fibers as compared to their unmodified counterparts was demonstrated, particularly by a high strain test in the glassy state. This confirmed the enhanced filler/matrix interface observed in such materials during the process and in the final composite as analyzed by SEM. No significant difference in reinforcing capability of the two kinds of filler was observed in the DMA analysis.

This study was performed to determine the effect of boric acid treatment upon the decay resistance and mechanical properties of poplar wood. Test specimens were prepared from poplar wood (Populus nigra L.) to meet ASTM D 143-94 and BS 838:1961 requirements. Samples were impregnated with boric acid solution (0.5, 1, and 2% w/w in distilled water) and by a long-term (21 days) dipping technique to reach complete saturation. Impregnated specimens were exposed to rainbow white-rot fungus (Trametes versicolor) for 14 weeks according to BS 838:1961 as applied by the kolle-flask method. The weight loss, compression strength parallel to the grain, and Brinell hardness were determined after impregnation and exposure to white-rot fungus. The highest weight loss (28.60%) was observed for untreated control samples and the lowest (0.63%) occurred in samples treated with 2% boric acid solution. The highest compression strength parallel to the grain was noted in samples treated with 0.5% boric acid and decayed (22.59 MPa) and the lowest compression strength parallel to the grain was recorded in untreated decayed samples (10.42 MPa). The highest Brinell hardness on tangential surface was observed in samples treated with 1% boric acid and decayed (1.32 KN) and the lowest was noted in untreated decayed samples (0.39 KN). The highest Brinell hardness on radial surface was observed in samples treated with 1% boric acid and decayed (1.07 KN) and the lowest was found in untreated decayed samples (0.35 KN).

This paper presents the production of xylooligosaccharides from auto-hydrolysis liquors of wheat straw and sunflower stalk, as wells as the antioxidant activity of these autohydrolysis liquors. The autohydrolysis liquors (raw or refined by ultrafiltration) of both wastes were subjected to the action of two different endoxylanase to produce xylooligosaccharides with low degree of polymerization that are potentially useful as food additives. Trichoderma reseei xylanase led to the highest proportion of oligomers with degree of polymerization values in the range 1–3, while Aspergillus niger xylanase gave mainly oligomers with polymerization degree in the range 2-3. T reseei xylanase gave a higher increase in equivalent xylose concentration and produced more monosaccharide than A.niger xylanase. Membranes with a nominal MWCO 1 kDa did not reject antioxidant-related and other low molar mass compounds, and most of these compounds were recovered with monosaccharides in the permeate of the membrane.

Polyaniline (PAn)-coated conductive paper was prepared by in-situ polymerization of aniline and a two-step process. XPS results confirmed that the bond between PAn and cellulose existed in the form of hydrogen bonding. The mild treatment did not result in the oxidation and degradation of cellulose. Decreased bonding strength of conductive paper was attributed to the coverage of hydroxyl groups on pulp fibers by PAn. For the PAn-coated paper about one in every three nitrogen atoms was doped with p-toluenesulfonic acid (PTSA). The quinoid imine nitrogens of the PAn molecular chain were preferentially doped. Pulp fibers seemed to be favorable for the doping of PAn with PTSA. The surface resistivity sharply decreased at least two orders of magnitude with a very small increase in the amount of PAn coated (from 3.6% to 4.2%). A continuous conductive network was formed and the surface resistivity was lowest when the amount of PAn coated reached 30.1%. The upper and lower threshold values were around 4% and 30%, respectively. SEM study showed that the shape of the PAn coated on pulp fibers was spherical with a diameter from 100 to 200 nm.

In this work the annual plant called Luffa cylindrica (LC) has been characterized and used to prepare macroscopic lignocellulosic fibers and cellulosic nanoparticles, viz. microfibrillated cellulose (MFC) and whiskers, each of which can be used as a reinforcing phase in bionanocomposites. The morphological, chemical, and physical properties of LC fibers were first characterized. The contents of lignin, hemicellulose, and other constituents were determined, and scanning electron microscopy (SEM) observations were performed to investigate the surface morphology of the LC fibers. Sugars contents were determined by ionic chromatography, and it was shown that glucose was the main sugar present in the residue. MFC and whiskers were prepared after chemical treatments (NaOH and NaClO2), purifying cellulose by eliminating lignin and hemicellulose. Transmission electron microscopy (TEM) and SEM made it possible to determine the dimensions of LC whiskers and MFC. Tensile tests were carried out to investigate the mechanical properties of LF nanoparticles.

An integrated approach was studied for in-house cellulase production, pretreatment, and enzymatic conversion of sugarcane bagasse into glucose followed by the production of second generation bioethanol. Solid state cultures of Aspergillus sp. S4B2F produced significant levels of cellulase complex on wheat bran, supplemented with 1% (w/w) soyabean meal, moistened with 1.5 parts of distilled water after 96 h of incubation at 30oC. The highest productivities of endoglucanase, exoglucanase, and β-glucosidase were 66, 60, and 26 IU/g of fermented dry bran, respectively. The enzyme components had a temperature and pH optima at 50oC and 4.0, respectively and revealed high thermostability at 50oC, retaining 66, 54, and 84% residual activities after 72 h. Pretreatment with 2% alkali in combination with steam was the most efficient pre-hydrolysis method for enzymatic bioconversion and fermentation of cellulosic residue of sugarcane bagasse, which produced the highest cellulose conversion (67%), with glucose and alcohol yields of 323 mg and 175 ml respectively per dry gram of bagasse.

Rice straw fiberboard was made using 12 wt % urea-formaldehyde (UF) resin as binder and 1.0 wt % polymeric methylene diphenyl diisocyanate (pMDI) and 1.2 wt % wax emulsion as water retardants. The prepared fiberboards were heat-treated at 120, 150, 185, and 210°C in the presence of steam in a high-temperature dry kiln, respectively for 90 min. The effect of water retardants and heat treatment on the water resistant and some mechanical properties of the fiberboards were investigated. It was found that the water resistance of the rice straw fiberboard could not be improved by adding wax emulsion. The use of pMDI to the system significantly increased the interfacial strength and reduced 24-h thickness swelling (TS) compared to the boards with or without wax emulsion. After heat treatment, the TS was significantly decreased due to the decrease in the free reactive hydroxyl group content of rice straw fiber. Some mechanical properties of the fiberboards, such as the internal bonding strength, modulus of elasticity, and modulus of rapture were dramatically reduced with increasing temperature from 120°C to 210°C.

Three hybrid systems were compared to a solvent-based low-VOC system. The goal of the project was to determine if the hybrid systems met the requirements of the kitchen cabinet and furniture industries. Adhesion of each system to the substrate was first evaluated, and significant differences were recorded. Subsequently, resistance to heat and moisture was evaluated using hot box and hot and cold check tests. These tests indicated that the experimental systems generally performed relatively well in terms of thermal resistance, but the appearance of those prepared from solvent-borne sealers and lacquers were less stable. The chemical resistance of these systems was also studied. The ability of the finish to withstand the effects of substances typically found in a kitchen was tested, as was their resistance to detergents and water. All the systems performed very well in vertical testing. Volatile organic compound emissions were finally measured after conditioning times of 3 and 21 days. These tests showed that the different systems behaved quite differently. The systems prepared with solvent-borne sealers and lacquers produced a high level of VOCs at the beginning of the test, with a rapid decrease thereafter, while the opposite was observed in systems based on water-borne sealers and lacquers.

Using a multi-effect evaporation system to concentrate the effluent from alkaline peroxide mechanical pulping (APMP) plants is known to require a high energy consumption. In order to improve the situation, a polyethersulfone membrane was used to concentrate the effluent of APMP plants beforehand. An orthogonal experimental design was applied and a mathematical model was established to optimize the filtration parameters. An estimation of potential energy and water savings from this new concentration process was developed. The optimal filtration conditions obtained were: molecular weight cut-off at 10,000 Dalton, trans-membrane pressure at 3 bar, feed temperature at 50oC, cross-flow velocity at 420 rpm, and volume reduction factor at 0.93. The average permeate flux under these conditions was 45.31 l/m2.h. The total solids content was increased from 14.74 g/l in the feed to 95.04 g/l in the concentrate. The permeate had low total solid contents of 8.75 g/l, Chemical Oxygen Demand of 6696 mg/l, and Biochemical Oxygen Demand of 4383 mg/l. Such qualities would allow the permeate to be reused in the alkaline peroxide mechanical pulping process. With this new concentration process, about 4840.6 kwh energy can be saved and 23.3 m3 effluent discharge can be reduced for each ton of pulp produced.

Recent studies on the ultrastructure and composition of the gelatinous layer (g-layer) in poplar have reported findings of xyloglucan. Using correlated fluorescence, scanning- and transmission electron micros-copy, we found evidence for xyloglucan present in and surrounding the g-layer, using the fucosylated xyloglucan specific CCRC-M1 antibody and the carbohydrate binding module FXG-14b. However, labeling of isolated gelatinous layer remained negative.