Research Articles

Nine soluble polysaccharide fractions were sequentially extracted with hot water at 80, 100, and 120 °C for 3 h, and 60% aqueous ethanol containing 0.25, 0.50, 1.00, 2.00, 3.00, and 5.00% NaOH at 80 °C for 3 h from dewaxed bamboo (Dendrocalamus brandisii) sample, and their chemical compositions and physicochemical properties were examined. The sequential treatments yielded 20.6% soluble polysaccharides of the dry dewaxed bamboo material. Molecular weight and neutral sugars analysis revealed that the soluble polysaccharides were mainly composed of arabinoglucuronoxylans and amylose starch. Spectroscopy (FT-IR, 1H, 13C, and 2D-HSQC NMR) analyses suggested that the isolated arabinoglucuronoxylans from bamboo (D. brandisii) could be defined as a linear (1→4)-β-linked-xylopyranosyl backbone to which α-L-arabinofuranose units and/or short chains of 4-O-methyl-glucuronic acid were attached as side residues via α-(1→3) and/or α-(1→2) linkages. In addition, it was found that the thermal stability of polysaccharides increased with an increment of their molar mass.

The effects of moulding pressure and initiator content on the performances of kraft fibre-reinforced UPE composites were investigated by means of tensile evaluation, DMA analysis, SEM analysis, and short-term creep tests. The results indicated that the prepared composites had much higher tensile strength and modulus and better creep resistance than traditional thermoplastic wood plastic composites (WPCs). These improved properties resulted from the incorporation of the strong kraft fibres as reinforcement. The combination of the fibers with the thermosetting UPE matrix produced enhanced kraft-UPE interfacial adhesion. Changes in moulding pressure and initiator level produced various effects in the properties of composites. As the moulding pressure increased from 6 MPa to 25 MPa, the mechanical properties and creep resistances increased gradually until a moulding pressure of 20 MPa was reached; after this point, the values decreased. With an increase in the initiator content from 0.3 PHR (parts per hundred parts of resin) to 1.0 PHR, the tensile strength and interface adhesion first increased, then decreased, while the instantaneous strain and maximum strain values (measured in the creep tests) decreased gradually.

Bark, as a residue from trees, is mostly used for thermal energy production, but a better utilization of this resource was considered as an alternative raw material for wood-plastic composites (WPCs). The influence of bark, wood, and blending of bark and wood flour content of the poplar tree on the mechanical characteristics of WPCs were investigated. Wood and bark flours with 2% maleic anhydride-grafted polypropylene (MAPP) and polypropylene were compounded into pellets using a counter-rotating twin-screw extruder, and test specimens were prepared by injection molding. The results showed that both bark fiber and wood flour increased mechanical strength (flexural strength (MOR), flexural modulus (MOE), tensile modulus, and tensile strength) significantly (P<0.05). Composites made with bark flour exhibited lower mechanical strength compared to those made with wood flour and wood flour/bark flour. Differences in chemical composition between bark and wood, fines, low aspect ratio (length/width) of bark flour, delamination between fines and matrix, and the lower intrinsic fiber strength of bark fibers compared to wood fibers are good explanations for this demarcation. The notched impact strength of all reinforced composites was significantly lower than neat polypropylene (P < 0.05).

Pretreatment of straw separated from cattle and horse manure using N-methylmorpholine oxide (NMMO) was investigated. The pretreatment conditions were for 5 h and 15 h at 120 °C, and the effects were evaluated by batch digestion assays. Untreated cattle and horse manure, both mixed with straw, resulted in 0.250 and 0.279 Nm3 CH4/kgVS (volatile solids), respectively. Pretreatment with NMMO improved both the methane yield and the degradation rate of these substrates, and the effects were further amplified with more pretreatment time. Pretreatment for 15 h resulted in an increase of methane yield by 53% and 51% for cattle and horse manure, respectively. The specific rate constant, k0, was increased from 0.041 to 0.072 (d-1) for the cattle and from 0.071 to 0.086 (d-1) for the horse manure. Analysis of the pretreated straw shows that the structural lignin content decreased by approximately 10% for both samples and the carbohydrate content increased by 13% for the straw separated from the cattle and by 9% for that separated from the horse manure. The crystallinity of straw samples analyzed by FTIR show a decrease with increased time of NMMO pretreatment.

Lignin was obtained from black liquor samples from soda-AQ pulping of oil palm empty fruit bunch (EFB) fiber. Oil palm EFB reinforced epoxy composite samples with varying lignin content of 15, 20, 25, and 30% as curing agent were prepared. The chemical structures of lignin were characterized by FT-IR, and CHN analysis. FT-IR and CHN analysis confirmed structural changes of epoxy resin after use of EFB-lignin as curing agent in epoxy resin. Thermal analysis of composites was carried out by thermogravimetric analysis (TGA). The TGA graphs showed that crosslinking of epoxy and lignin as curing agent may induce relatively high-chain rigidity in the polymer and may result in an enhanced thermal stability of the EFB/lignin-epoxy composite systems. The mechanical properties (tensile, flexural, and impact behavior) and physical properties (water absorption) of the composite samples were evaluated. Mechanical properties of epoxy composites cured with 25% lignin were found to be higher than that of the composite prepared from a commercial curing agent. Scanning electron micrographs showing tensile fracture of the composites showed evidence of good fiber–matrix interaction, induced by the curing agent.

Reducing basis weight could lead to huge savings of forest resources as well as energy consumption and waste treatment in the papermaking process. However, low basis weight paper generally lacks normal strength and stiffness. The lower the basis weight of the paper, the more important is surface sizing. Highly cross-linked cured epoxy resin, due to its epoxy group and phenyl group, has gained such outstanding mechanical properties and dimensional stability that it could be utilized to enhance paper strength and stiffness through surface sizing when incorporated with oxidized starch. In this study, the impacts of sizing volume, fluid temperature, curing agent, and curing system dosage on sizing were investigated. Our results indicated that a rigid resin layer and interpenetrating polymer network formed on the surface and in the inner layer of the paper, respectively. The formed resin layers strongly support the paper and thus resulted in the improvement of strength and stiffness.

The beta-O-4 bond cleavage of a non-phenolic β–O-4 type dimeric lignin model compound, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl)-ethanol (III), was examined in systems using potassium tert-butoxide as a base (0.5 mol/l) and tert-butanol (tBuOH), dimethylsulfoxide, 1,4-dioxane, or tetrahydrofuran as a solvent. The β–O-4 bond of compound III was cleaved in any system at 30°C, and 2-methoxyphenol (II) was liberated. The amount of compound II liberated was close to the quantitative yield on the basis of the amount of compound III that disappeared, except for the treatment in the t-BuOH system. The reaction rate was dependent on what solvent was used. Half-life periods for these systems were roughly about 6.0, 3.0, 0.7, and 0.2h, respectively. It seemed that the rates were very high when the polarity of the solvents was low. Two reaction products generated from the aromatic ring with two methoxyl groups of compound III, 4-acetyl-1,2-dimethoxybenzene and 3,4-dimethoxybenzoic acid, were detected in all the systems. A peculiar reaction product, 1,2-dimethoxybenzene, was detected in a fairly large quantity, only when the latter two solvents with low polarities were applied.

Poplar (Populus alba L.) lumber with a nominal thickness of 7 cm from the Taleghan region in Iran was dried through convective kiln drying and under three different programs of T5–D2 (Forest Product Laboratory proposed program for poplar), T5–D4, and T5–D6 in order to obtain the optimum kiln schedule so as to protect the wood quality at an appropriate level up to final moisture content of 12±2%. Subsequently, the intensities of warps, superficial and internal cracks occurrence, residual stresses, drying rate, and final moisture gradient were measured. Results revealed that due to low warping values, more homogeneous final moisture profile, fewer internal cracks, and absence of superficial cracks in the program T5–D2 compared to the other two (T5–D4 and T5–D6), this program can be recommended as an optimum program for poplar lumber drying at commercial scale from the Taleghan region. On the other hand and from an energy efficiency point of view, in comparison with the mild schedule (T5-D2), the severe schedule (T5-D6) by saving 456 h of drying time, reduced electricity consumption by 6156 KWh and was therefore found to be $ 240.08 more profitable in this trial.

The aim of this work was to examine the influence the lignin component of wood on the photodegradation of high-density polyethylene (HDPE) in wood/HDPE (WPE) composites. The neat HDPE and wood/HDPE composites were prepared using a twin screw extruder followed by an injection moulder. The lignin content was varied from 0 to 29 %wt. of wood by the addition of delignified wood pulp into wood flour. The results suggested that the photodegradation of HDPE in WPE composites was accelerated by the presence of lignin; the chromophoric groups in the lignin enhanced UV adsorption onto the WPE composite surface. The carbonyl and vinyl indices, color, percentage crystallinity, and the melting temperature increased when the lignin contents were increased. The color fading in WPE composites resulted from photobleaching of lignin. In addition, the presence of lignin led to the development ofl cracks in WPE composites, especially at high lignin contents. For the effect of UV weathering time, the carbonyl and vinyl indices, discoloration, and percentage crystallinity increased as a function of UV weathering times, whereas the melting temperature of HDPE in both neat HDPE and WPE composites and water absorption of specimens decreased; the wood index in WPE composites increased during the initial UV weathering times and then decreased at 720 h weathering time.

Encapsulation of methane-producing bacteria was carried out with the objective of enhancing the rate of biogas production. Encapsulation with a one-step liquid-droplet-forming technique was employed for the natural membrane, resulting in spherical capsules with an average diameter and a membrane thickness of 4.3 and 0.2 mm, respectively. The capsules were made from alginate, using chitosan or Ca2+ as counter-ions, together with the addition of carboxymethylcellulose (CMC). A Durapore® membrane (hydrophilic PVDF) with a pore size of 0.1 µm was used for synthetic encapsulating sachets having width and length dimensions 3×3 and 3×6 cm2 for holding the bacteria. During the digesting process, the dissolved substrates penetrated through the capsule membrane, and biogas inside the capsules was able to escape by diffusion. The results indicate encapsulation to be a promising method of digestion, with a high density of anaerobic bacteria. The method holds considerable potential for further development of membranes and their applications.