Research Articles

Soda lignin was divided into two fractions with different molecular weights by methanol extraction. Lignin amine was synthesized from the low-molecular-weight lignin fraction via Mannich reaction and was used for interfacial modification of poly-(vinylchloride) (PVC)/wood-flour composites. The PVC/wood-flour composites were prepared from surface-treated wood flour and PVC by melt compounding. The lignin amine treatment provided almost equivalent improvement in mechanical performances of composites as aminosilane treatment does. The tensile and impact strengths of composites prepared from 30phr of wood flour treated with 2wt% lignin amine were increased by 21.0% and 43.9%, respectively, compared to those prepared from untreated wood flour. Furthermore, lignin amine treatment could also significantly reduce the water absorption of composites. A significant increase in storage modulus (E’) was observed upon incorporation of wood flour with lignin amine treatment. The improved dispersion of wood flour in polymer matrix was observed by SEM images when the wood flour was treated by lignin amine. The experimental data indicate that the polymer-wood interfacial combination is strengthened.

An activation process involving chitosan was conducted to prepare electroless nickel plated wood veneers for electromagnetic interference (EMI) shielding. In this process Pd(Ⅱ) ions were ed on wood surface modified with chitosan. Then they were reduced and dipped into a plating bath in which Ni-P co-deposition was successfully initiated. The coatings were characterized by SEM-EDS and XRD. The metal deposition, surface , and electromagnetic shielding effectiveness were measured. The morphology of the coating observed by SEM was uniform, compact, and continuous. EDS results showed that the coating consists of 1.8 wt.% phosphorus and 98.2 wt.% nickel. XRD analysis indicated that the coating was crystalline, which is supposed to be related to the low phosphorus content. The plated birch veneers exhibited electro-conductivity with surface resistivity of 0.24 Ω·cm-2 and good electromagnetic shielding effectiveness of over 50 dB in frequency range from10 MHz to 1.5 GHz.

Particleboard and medium density fiberboard (MDF) panels were produced using stone pine (Pinus pinea) cones, which were mixed with either wood particles or fibers from pine and beech wood at various ratios. Specimens from the panels were subjected to AWPA E10-06 soil-block tests using two brown-rot fungi, Gloeophyllum trabeum and Postia placenta and two white rot fungi, Trametes versicolor and Pleurotus ostreatus for 12 weeks. Specimens were also subjected to subterranean termites, Coptotermes formosanus, according to the JIS K 1571 standard test method for 3 weeks. Pinecone material in the furnish had no considerable effect on the decay resistance of particleboard and MDF specimens subjected to the brown-rot fungi; however, mass losses in the specimens exposed to the white-rot fungi were gradually decreased as the pinecone ratio in the furnish increased. No increased resistance was observed in the specimens exposed to the termites. In some cases, the specimens containing pinecone furnish had greater mass losses compared to the control specimens.

The damping coefficient of the first mode in the longitudinal vibration of mulberry and walnut woods was characterized to find justifications for the water soaking of woods in traditional musical instrument industries in Iran. Visually clear and sound beams were prepared from Morus alba and Juglans regia, and the damping coefficient in the temporal field was evaluated before and after three continuous cycles of soaking of specimens in distilled water (24 hours, pH 7, and temperature 50 oC). Experiments were conducted with free longitudinal vibration using the free-free bar method in 360 × 20 × 20 (L ×R ×T) dimensions. Soaking cycles homogenized and decreased the damping coefficient in both species. On the basis of such results, the suitability of water soaked specimens is discussed in traditional musical instrument industries in Iran, taking into the account the longitudinal sound velocity, modulus of elasticity, and density affecting the acoustic limits. These two series of testing specimens were suitable in resonators and xylophone bars for backs, sides, and ribs and not for top plates, unless as the outstanding piece, since they marginally meet the density, sound velocity and damping coefficient limits qualified for those applications.

Aspergillus niger NCIM 1207 produced significantly high levels of β-glucosidase and β-xylosidase activities in submerged fermentation. Cellulose induced only β-glucosidase, while xylan induced both β-glucosidase and β-xylosidase activities. Both the enzymes of this strain were found to undergo catabolite repression in the presence of high concentrations of glucose and glycerol. The sudden drop in pH of the fermentation medium below 3.5 caused the inactivation of enzymes when the fungus was grown in glycerol-containing media at lower temperatures. The growth of the organism at 36 oC led to an increase in pH of the fermentation above 6.0 that affected β-xylosidase activity significantly. Highest levels of β-glucosidase ((19 IU mL-1 or 633 IU g-1 of substrate) and β-xylosidase (18.7 IU/mL-1 or 620 IU g-1 of substrate) activities were detected when A. niger was grown at 30 oC for first five days followed by further incubation at 36 oC. Such a process of growing the organism at lower temperatures (growth phase) followed by producing the enzymes at higher temperatures (production phase) in case of fungal systems has not been reported so far. The zymogram staining of the β-glucosidase demonstrated that A. niger produced only single species of β-glucosidase. We feel that A. niger NCIM 1207 is a potential candidate to produce both β-glucosidase and β-xylosidase in high amounts that can be used to supplement commercial cellulase preparation.

The addition of a phosphonated chelant (DTPMPA) at different points of a TCF bleaching sequence and its effect on pulp properties were studied in this work. An industrial Eucalyptus grandis kraft pulp was submitted to a counter-ion exchange (Ca2+ or Na+ form) and was then bleached using DTPMPA in the washing or in the bleaching stages of two distinct sequences: OOpP and OQOpP (20 pulps). The counter-ion exchange affected fibre length, as well as the handsheets bulk and air permeability (higher for Na+-based pulps) and handsheet tensile strength, brightness, skeletal density, and total porosity based on Hg porosimetry (higher for Ca2+-based pulps). The hydrogen peroxide consumption in Op and P stages achieved the lowest values when the chelant was distributed rather than applied in a separate Q stage. The addition of chelant in the P stage provides pulps with higher ISO brightness (>85%). The chelant effects were always more noticeable in Ca2+-based pulps.

Bamboo timber is very vulnerable to mould fungi, a characteristic that is attributed to the rich sugar, starch, and protein present in bamboo. Solvents including cold water, hot water, benzene/ethanol, ethanol/ether, 1% NaOH, and 1% HCl can dissolve corresponding components from bamboo, which might be helpful to the resistance of bamboo against mould fungi. In order to study the relationship between surface nutrition and mildew of bamboo, mould resistances of bamboo blocks treated with different solvents were tested in the laboratory and field. Results showed that bamboo treated with cold water, hot water, benzene/ethanol or ethanol/ether had almost the same resistances with the controls against mould fungi, and the surfaces became covered with mycelium within 10 days in laboratory tests, and 5 weeks in field tests. 1% NaOH and 1% HCl were helpful to the mould resistance of bamboo, of which, 1% HCl treatments behaved the best, especially in the s.

This paper reports on the synthesis of Cannabis indica fiber-reinforced composites using Urea-Resorcinol-Formaldehyde (URF) as a novel matrix through compression molding technique. The polycondensation between urea, resorcinol, and formaldehyde in different molar ratios was applied to the synthesis of the URF polymer matrix. A thermosetting matrix based composite, reinforced with lignocellulose from Cannabis indica with different fiber loadings 10, 20, 30, 40, and 50% by weight, was obtained. The mechanical properties of randomly oriented intimately mixed fiber particle reinforced composites were determined. Effects of fiber loadings on mechanical properties such as tensile, compressive, flexural strength, and wear resistance were evaluated. Results showed that mechanical properties of URF resin matrix increased considerably when reinforced with particles of Cannabis indica fiber. Thermal (TGA/DTA/DTG) and morphological studies (SEM) of the resin, fiber and polymer composite thus synthesized were carried out.

This study was carried out to determine the effects of adhesive ratio and pressure time on thickness swelling (TS), internal bond (IB), modulus of rupture (MOR), and modulus of elasticity (MOE) properties of oriented strand board (OSB). For this purpose, 80 mm long strands made of Scots pine (Pinus sylvestris L.) were bonded with phenol-formaldehyde resin at three different ratios (3, 4.5, and 6%) to produce three-layer cross-aligned OSBs. Strands used for the production of OSB panels were made up 40% of core layer and 60% of outer layers. The panels were pressed for three different press times, from 3, 5, to 7 minutes, under 0.4 MPa pressure, aiming for a target density of 0.70 g/cm3. TS, IB, MOR, and MOE properties of OSB panels were evaluated according to the standards (TSE EN 117-319-310). Results showed that MOR and MOE values were changed in the ranges 25.31 to 42.27 N/mm2, and 2848.90 to 6545.63 N/mm2, respectively. Also, the results showed that as adhesive ratio and pressure time increased, the TS, MOR, and MOE values increased too.

Studies on the softening behavior of in situ lignin of normal wood in a given species have never been performed before due to the relatively narrow lignin content and lignin structural variation within one species. Using transgenic trees with different levels of lignin content and/or syringyl to guaiacyl propane (S/G) ratio helped us to overcome this problem. Submersion three-point bending and parallel-plate compression-torsion dynamic mechanical analyses were conducted on one-year-old wild type and transgenic aspen (Populus tremuloides Michx.). The different genetic modifications included groups with reduced lignin content, increased S/G ratio, and both reduced lignin content and increased S/G ratio. Measurements with both methods revealed a statistically significant decrease in glass transition temperature in the reduced-lignin genetic group compared to the wild-type. Increase in the S/G ratio did not affect the thermo-mechanical properties; these results contradict claims that increasing the methoxyl groups would reduce lignin cross-linking and the glass transition temperature.