IRANIAN JOURNAL OF WOOD AND PAPER INDUSTRIES
Year:2010 | Volume:1 | Issue:1|Papers Count:8

In this research, water absorption and thickness swelling behavior of hydrothermally modified fiberboard (MDF). Were evaluated Fibers were treated in a stainless steel reactor at temperatures of 120, 150 and 180°C for holding times of 0, 30 and 90 min. Test boards were prepared based on the target density of 0.7g/cm3 at the press temperature of 175°C as well as the pressure of 30 bar and the press time of 5 min. Urea formaldehyde (UF) resin was applied at 10% based on the fibers dry weight. Test samples (10´20´20mm) were cut from the boards, dried in an oven and soaked in the water. Water absorption, thickness swelling and their rates were measured in the soaked samples.Results revealed that increase of the treatment temperature caused decrease of water absorption and thickness swelling in the treated boards except in samples treated at 120°C. It was also indicated that increase of the holding time did not significantly affect water absorption and thickness swelling.

As the outdoor application of Wood Plastic Composites (WPCs) become more widespread, the resistance of these products against weathering, particularly ultraviolet (UV) light becomes more important. When WPCs are exposed to outdoor ultraviolet light, rain, snow and atmosphere pollution, they will be degraded which can be indicated by color fade. To investigate the effects of methylation and Anti-Oxidant separately and together on discoloration of weathered wood plastic composites, composites of poplar wood flour and high density polyethylene.Were made according to the ASTMD 2565, samples were placed in Atlas Xenon apparatus for 250 and 2000 hours. Discoloration and FT-IR spectra of the samples were measured and compared.The results have shown that methylation in short term and long term can relatively reduce the discoloration of weathered samples and also in short term can hinder the photodegradation. FT-IR spectra showed that, in long term, neither of the treatments could protect lignin from irradiation within wood flour. But methylation limited the depth of penetration of weathering. The Antioxidant did not have an influence on color change in a long period of time, but was able to relatively decrease it in short term.

In order to perform a qualitative and quantitative investigation on tannic acid content in Oak bark, the bark samples were collected from Educational Forest of Gorgan Agricatural Science and Natural Resources University. Solvents were used in laboratory to extract tannin and were considered as variables. Regarding diversity of bark components, Tappi Test Method (T264-om-88) was used to determine extractives contest. Twenty grams dry material was placed in a soxhelt. Extracted material with hot water, methanol and water methanol (1:1) solvent were 25±2, 20±2 and 18±2 percents respectively. Tannic acid existance in extracts was determined using High Performance Liquid Choromatography (HPLC) and types of bonds were determined using FT-IR. Results showed that water methanol solvent was the best solvent for extracting tannin.the amount of extracted tannic acid in maximum wavelength of 250 nm and using gradient system, in solvent water methanol, methanol and hot water solvent were 70±2, 30±2 and 5±2 precents, respectively. Amount of tannin in the bark using solvent water-methanol was determined to be 14 perecents that was the highest amount.

Effect of immersion temperature on long-term water uptake behavior of HDPE/wood sawdust Composite was studied in this research. Panels of wood plastic composites (WPCs) were manufactured from a mixture of sawdust of wood and High density polyethylene powder at 60% by weight filler loading at constant temperature and pressure using a dry blend/hot press method. The nominal density and dimensions of the panels were 1g/cm3 and 35´35´1 cm3, respectively. Specimens were cut from the panels based on DIN-EN 317 standard. The prepared specimens were immersed in distilled water at 20, 40 and 60°C to measure long-term water absorption. The results showed that water absorption in HDPE/wood sawdust composite proved to follow the kinetics of a Fickian diffusion process. By increasing the immersion temperature, the time to reach to maximum value of water absorption decreased and maximum value of water absorption increased. Diffusion coefficients were affected parabolically by immersion temperature.

Wood resin of mixed tropical hardwoods (MTH) Kraft pulp was removed and characterized. Characterization of wood resin from different pulping stages was achieved accurately using Pyrolytic Gas Chromatographic-Mass Spectrometry (Py-GC-MS). Two types of resin were recognized: (1) small fraction of unreactive and inaccessible damar resin which was only found to be concentrated in centri-cleaner reject, (2) large fractions of fatty acids, fatty alcohols, and sterols. These can be removed chemically, e.g. by surfactant addition. Results of experiments showed that addition of surfactant enhances removal of extractives and decreases the chemical consumption during bleaching stage.

The current research explains an innovated technique to enhanced mechanice properties of poplar wood by combination of two modification techniques, hydrothermal and mechanical. Blocks of 50´55´500mm3 were cut from poplar wood and treated in a reactor at 120, 150 and 180°C for 30 min. Afterwards, the blocks were pressed at 180°C for 20 min at a pressure of 80 bar to achieve a compression set of 60% in radial direction. Density and bending properties (moduli of elasticity and rupture) as well as impact resistance were determined in the specimens and compared with those of the untreated one.Results revealed that the density, modulus of elasticity and impact load resistance increased as the treatment temperature rose. The highest density, modulus of elasticity and impact resistance were determined in samples treated at 150°C. The modulus of rupture was increased as the temperature was raised up to 120°C and then it was reduced as low as the untreated one at higher temperatures.

The influence of concentration (2, 3 and 5%) of Maleic Anhydride Grafted Polypropylene (MAPP) on long term water absorption and thickness swelling of wood flour/E-glass fiber Hybrid polypropylene composites were studied. The samples (strips with 10 mm thickness and 70 mm width) were made using a laboratory twin-screw extruder. Long term water absorption and thickness swelling kinetics of manufactured hybrid composites were evaluated by immersing them in water at room temperature for several weeks. Water diffusion coefficients and thickness swelling parameter (KSR) were calculated by evaluating the water absorption isotherms. The results showed that increase in MAPP content to 2 and 5% significantly decrease maximum water absorption, thickness swelling, water diffusion coefficients and KSR of the composites. Water diffusion coefficient of the studied composites was proved to follow the kinetics of a Fickian diffusion process.

The dimensional stability of wood is an important property for outdoor applications. In this study, the dimensional stabilization of poplar wood (Populus Alba) by applying emulsion of paraffin, quaternary ammonium and starch was investigated. Paraffin at three levels of 0%, 3%, 5%, quaternary ammonium at three levels of 0%, 1.5%, 2.5% and starch at three levels of 0%, 1% and 2% were selected as variables. Some physical characteristics including longitudinal, tangential and radial swelling were determined. Based on the results, for optimizing physical properties, the treatment of 5% paraffin, 0-1.5% quaternary ammonium and 0-1% starch was recommended.