مجله تحقیقات علوم چوب و کاغذ ایران
سال بیست و پنجم شماره 2 (پیاپی 33، پاییز 1389)

The use of corn stalk residues in combination with poplar wood for particleboard production is investigated. Four combinations of corn stalk and P.nigra particles (100% corn stalk; 75% corn stalk, 25% poplar wood; 50% corn stalk, 50% poplar wood and 25% corn stalk, 75% poplar wood) is used. Two resin contents of 10 and 12% and two press temperatures of 170 and 180 C were employed. The results showed that increasing press temperature from 170 to 180 C, decreased both MOR and MOE of boards and increasing resin content from 10% to 12%, improved MOR. When the ratio of poplar wood to corn stalk increased, both MOR and MOE of the boards increased and the highest values were reached at 50% and 75% poplar wood. Higher press temperature and lower ratio of corn stalk improved internal bond (IB). Higher press temperature, resin content and lower ratio of corn stalk, decreased thickness swelling. Based on the results, with the application of either 25% to 50% corn stalk and press temperature of 170 C, standard particleboard can be produced.

In this investigation chemical, physical, morphological, pulp and paper making characteristics of Populus costanzo were investigated. The average dry and critical specific gravity was found as 0.39 and 0.36. The fiber morphology include fiber length, diameter, lumen and thickness of cell wall were determined as 1.14 mm, 28.84 µm, 28 µm and 2.92 µm respectively. The average chemical composition were measured as cellulose 50.74%, lignin 19.18%, Ext. 1.22% and Ash 1.65%. Kraft Process was used for Pulping. The maximum yield and kappa number of Populus costanzo at 1 hour cooking time, 150°c cooking temperature and 12% effective alkali conditions were obtained as 61.91% and 54.83% respectively. While minimum yield and kappa number following 3 hour cooking, 170°c cooking temperature and 16% effective alkali condition, obtained as 45.63% and 13.42 respectively.

Most industrial production processes need cooling water to operate efficiently and safely. Refineries, steel mills, petrochemical manufacturing plants, electric utilities and paper mills all rely heavily on equipment or processes that require efficient temperature control. Cooling water system control these temperatures by transferring heat from hot process fluids into cooling water. As this happens, the cooling water itself gets hot before reuse it must either be cooled or replenished by a fresh supply of cold water. The aim of this study was utilizing domestic wood in cooling towers structure. For this purpose, five wood species include: hornbeam, oak, alder, poplar and eldar pine different regions with different climate, include: power plant Montazer- Ghaem near Karaj, power plant Loshan north of Iran, power plant Dorcheh Esfahan in center of Iran and petrochemical manufacturing plants Bandar-Emam from south of Iran, were selected. Sampling were conducted and treated with CCA. All samples were put in the cooling towers and were tested during the study period. (Mechanical tests such as specific gravity, static bending, compression parallel to grain and hardness). Based on this study, the mechanical properties of these species during last four years were done. At the fifth year, there werent any virtual damages,while significant difference was achieved in terms of mechanical properties. Among the wood species, poplar and eldar pine had minimum mechanical degradation and that pinus eldarica had better quality than populus species.

The objective of adding reinforcing fillers such as natural fibers to plastics is to increase the strength compared with neat plastic and wood. In this research the effect of wood pulp fiber length (short, medium and long), aspect ratio and fiber content (27%, 37%, 47% and 0% (non-reinforced PP)) with 3% maleic anhydride grafted polypropylene on wood plastic composites (WPCs) has been studied. Results showed that increased fiber length or aspect ratio and fiber content increases mechanical properties (tensile strength, tensile modulus and MOE). Impact strength was inversely correlated with fiber content and fiber length, and that fiber content was more important factor than fiber length in this regard. The impact strength of composite of softwood pulps was much higher than wood floor composite plastic. The significant interaction between fiber length and fiber content, and lack of a specific trend in the treatments made assessment of the effect of fiber properties on MOR difficult.

An experiment was conducted to study polymerization conditions and important production factors, the amount of resin and press temperature on physical and mechanical properties of produced boards by urea formaldehyde (UF) and melamine urea formaldehyde (MUF) were compared. Purified UF resin (control treatment) and its mixture with MUF at 25, 50 and 75% proportions and at 170 and 180˚C temperatures were used to make homogen particle boards. The proportion of resin to particles was 10 percent by dry weight. Other production factors were assumed as fix factors. Eight experimental groups (treatment) with three replications per each were studied. Produced particles were derived from species Alnus subcordata. Physical and mechanical properties measurement prepared samples were based on European EN standard. Examined Physical characteristics include water absorption and thickness swell and mechanical characteristics were modulus of rupture, modulus of elasticity and internal bond. The data were analyzed in completely randomized design with factorial arrangement (4*2). Statistical significances among treatment means were determined by multiple range test of Duncan. The results of this study showed that physical and mechanical properties of boards were significantly improved by increasing the level of MUF resin and temperature. In sum, taking into account the quality and economical aspects of produced particleboard based on MUF resin as compared to that of control, we have concluded that 50 percent of MUF resin and 180 degree centigrade of press temperature are optimal levels.

The water repellency and dimensional stabilization of wood species are important for outdoor uses. In this study, the water absorption and water repelling of poplar wood (Populus alba) by emulsion of paraffin, Quaternary ammonium and starch, were investigated. Paraffin in three levels of 0%, 3%, 5%, Quaternary ammonium in three levels of 0%, 1.5%, 2.5% as well as starch in three levels of 0%, 1% and 2%(by weight) were selected as variables. A set of matched specimens were set aside as control, for making comparison. Results showed that the amount of paraffin had a significant positive effect on water absorption and water repellency that is increasing paraffin would improve these properties. Furthermore, specimens treated with paraffin had better water repellency than control samples. Based on the results, it is claimed that the treatment of 5% paraffin, 0-1.5% Quaternary ammonium and 0-1% starch will provide optimal water absorption and water repellency in treated specimen without any damage to other physical properties.

In this study, deinking of old newspaper by chemical and enzymatic methods was investigated. Chemical treatment was conducted using chemicals at different times of 10, 20 and 30 minutes, consistency of 10%, temperature of 50±1C along with washing, flotation and combination of washing/flotation. While, enzymatic treatment was accomplished at different concentrations of 0.025, 0.05, 0.1 and 0.2% of cellulase enzyme (on the basis of oven dried waste paper), pH range of 5-5.5, different times of 10, 15 and 20 minutes, consistency of 10%, temperature of 50±1C along with washing. The results of comparing optimal chemical and enzymatic treatments showed that, deinked pulp by chemical method provided higher brightness and yellowness. Also, deinked pulp by chemical method had provided papers with higher bulk, higher caliper as well as higher air resistance.

The heat transfer through three orthotropic directions and the evolution of temperature gradient in beech (Fagus orientalis) and spruce (Picea abies) during drying were investigated. Due to low capacity of dryer, small flat-sawn boards with dimensions of 80 × 25 × 40 mm (L×R×T) were used. Then, the boards were dried at the dry-bulb temperature of 60 °C and relative humidity of 50%. Four surfaces of the boards were coated by polyurethane-coated aluminum foil to confine the heat flux along one direction. Then, the boards were thermally insulated by 50 mm-thick styrofoam. Holes of 1mm diameter were made on the board specific distances to measure the temperature using thermocouple. The results showed that the temperature of each wood increased as heat up progressed until it reached the wet-bulb temperature. Then, it remained at an almost constant value as the wet bulb temperature until the wood moisture content reached the hygroscopic range. Furthermore, the pattern of the temperature profile for both wood species was almost identical. The surface temperature of the boards increased until it reached the dry-bulb temperature of 60 °C, while the core temperate remained as the wet-bulb temperature (48-52 °C) throughout the rest of drying period.

The suitability of wood and non-wood species for use in pulp and paper industry can be predicted by their morphological and chemical characteristics. In this research, morphological and chemical properties of four species of Ulmacea family, Ulmus glabra, Ulmus compestris, Zelkova carpinifolia and Celtis australis have been compared. Of each species, three cross section discs of 5 cm thickness were selected. Wood slivers of three zones: near to pith, middle part and near to bark wood were macerated in a mixture of acetic acid and hydrogen peroxide at 60°C for 48 hours. Biometric coefficients of fibers in three zones and four species have been measured and analyzed by a factorial, complete randomized block design. Results showed that, Zelkova carpinifolia wood has the least lignin, ash and extractives as well as the highest cellulose. The fibers of, Zelkova carpinifoliahas has the highest slenderness ratio, Runkel ratio and hence is most suitable species in Ulmacea family for paper industry. Fiber length and wall thickness near to bark zone was significantly higer compared to the pit zone. Therefore it is suggested that the mechanical properties of pulp of this three zones are different.

In this study, the influence of the fungus Coriolus versicolor on the durability of horn beam (carpinus betulus) in natural state and treated with chromated copper arsenate (CCA) was evaluated. CCA is a kind of water borne preservative that was used to treat specimens under vacuum and pressure (Bethel procedure) with amount of 3.5 & 1.5 percent on the basis of oven dry wood. Specimens were contaminated with the cultured fungus for eight weeks in incubator. After this period, weight reduction, compressive strength (parallel to grain) and hardness of specimens were measured. Weight reduction of treated samples with 3.5 & 1.5 percent CCA were 1.68 and 1.73 percent respectively. Weight reduction of control samples were much higher (22.87 percent) than treated ones. There was no significant difference between the Compressive strength (parallel to grain) of treated and control samples in the absence of the fungus but in the case of the samples affected by the fungus there were significant differences. Compressive strength (parallel to grain) of treated samples with 3.5 & 1.5 percent of CCA were 64.33 and 60.10 (Mpa) respectively but Compressive strength (parallel to grain) of control samples were much lower (38.44 Mpa) than treated samples. There was no significant difference between the hardness of treated and control samples without effect of fungus. On the other hand, the hardness of treated samples was slightly more than control samples, but this difference was not significant in 5 percent level. The hardness of treated and control samples with the effect of fungus have significant difference. Hardness of treated samples with 3.5 & 1.5 percent of CCA were 5788(N) and 5799(N) respectively. However hardness of control samples were much lower (3139N) than treated samples. Eventually CCA (Tanalith c) increased the durability of horn beam (Carpinus betulus) wood from nondurable level to a durable level.

In the course of enhanced bioremediation, addition of nutrients such as carbon, nitrogen, phosphorous, substrates, electron acceptors as well as vitamins (Thiamin, etc) and veratryl alcohol, increased metabolic activities will influence the production of enzymes and enhances the deterioration of pollutants. In this study, the effect of 1% (V/V) of nutrients containing various mineral salts, carbon (glucose and malt), nitrogen (casein peptone yeast extract) and some enzyme inducer such as veratryl alcohol and thiamin hydrochloride on production of laccase, peroxidase and xylanase enzymes by Phanerochaete chrysosporium in bagasse preparation effluent was investigated. The results showed that MSB+MCTV is the most effective additive which causes the highest lignolitic activity of this fungus after 5 to 7 days in the case of laccase and peroxidase and 3 days for xylanase, and maximizes the production of the enzymes. The production of these enzymes is measured at 78, 193 and 60 U/l respectively. However, in conditions no additive, the relevant values are 26, 54 and 16 U/l respectively. The relation between different stages of fungus growth and enzyme production as well as changes in lignin and carbohydrate of effluent after the period of nine days is also investigated

In order to manufacture wheat straw particleboards, different mixtures of UF and MF resins were applied. The ratio of UF: MF was 0:100,75:25,50:50,25:75 and 100:0 based on resin weight. Boards densities were set as 0.7gr/cm3.Physical and mechanical properties such as thickness swelling(TS) after 2 and 24 hours, internal bonding(IB), modulus of elasticity(MOE), modulus of rupture(MOR) were measured and compared to EN 312-4 standard. The highest amounts of IB, MOR and MOE were from the boards made of 50:50 (UF:MF). All of the boards MOE and MOR amounts of the treatments except for the treatment 100:0 (UF:MF) were in the range of EN 312-4 standard but the IB amounts did not comply. The TS amount was improved in the boards with more MF content but it was not in EN 312-4 range. Due to the thin waxy layer covers the outer most layer of wheat straw surface, the non polar structure of this layer brings low-compatibility between polar resins and wheat straw particles which will result in poor physical and mechanical properties for wheat straw particleboards. Also due to the low porosity of waxy layer, the penetration of polar formaldehyde resins into straw particles surface, not well occur and this is itself an important factor in low physical and mechanical resistance in wheat straw particleboards that in the case of wood.

The lignin dissolution in Kraft pulping for wheat straw was studied. Kraft pulping was carried out under the conditions: chemical charge of 18% (as NaOH, based on o.d. bagasse), sulfidity of 25% and liquor to wheat straw ratio of 10:1. Six cooking maximum temperatures of 85,100,110,120,130 and 150 ◦C, were selected and reaction time varied from 0 to 250 min., based on maximum temperature. The Klason lignin, acid soluble lignin, ash and extractive contents of wheat straw were 18.4%, 2.07%, 3.24% and 4.56% respectively. During alkaline pulping of wheat straw, 64% and 52% of lignin was removed before reaching to the temperature 100 ◦C and 85 respectively. The values for pulp and carbohydrates yield were, about 64%, 58% for 85 ◦C and 61%, 57% for 100◦C.

Effects of different humidity and heat content on the quality of corrugated board, was investigated. Optimal treatment variables include: corrugators speed (50, 100 and 150m/min), wrapping angle of the paper around pre heaters (90,180 and 300 degree) and moisture of paper (6.5%, 7% and 8.5%). Papers that treated for this purpose included: 125gsm Kraft liner, 127gsm medium paper and 140gsm test liner paper. A flute type of 3ply corrugated board was selected for this study. Moisture of paper was measured in 3 places: Paper on roll stand before single facer, paper after single facer pre heater and paper before incoming double facer in hot plate unit. Also temperature was measured in corrugator's rolls, hot Plates in double facer and final board after exiting of the machine. Results show that, warp of final board decreased in speed 50 and 100m/min, moisture 7% and 1800C wrapping angle of the paper around pre heater. That means lower speeds and higher wrapping angles cause more heat on corrugated board and decreasing in warp content resulted. It should be noted that lower humidity than 7% and increase wrapping angle over 180 degree cause over drying and intensive moisture decrease which in turn cause reverse warp in the final board.

The effect of using UF and MUF resins on physical and mechanical properties of particleboards made of rice straw and aspen particles was investigated. The aim of the study was to determine physical and mechanical properties of rice straw particleboard. Single-layer particleboard was produced with 11% MUF and 11% UF. In order to use UF and MUF, 2% hardener was added to adhesives. The Press condition for MUF was: 1750C for 4 minutes and for UF application was 1750C for 6 minutes. Another variable factor was the rice straw content in three levels (15%, 30% and 45%). Other factors such as board density (0/7gr/cm3) and mat moisture (12%) were the constants. The results indicate that increasing rice straw to wood particles cause some reduction in modulus of rupture, and internal bonding, and to some extent increase in thickness, swelling and water absorption of manufactured boards. But comparing and grouping means by duncan test showed that when up to 30% rice straw was added to wood particle these effects remained mostly insignificant. Particleboard bonded with 11% MUF had the highest bending strength. Particleboards bonded with MUF had better bending strength, shear strength, thickness swelling and water absorption after 2 and 24 hours immersion. Grouping the experimental data while using Duncan method was indicated the fact that an optimum condition for manufacturing particleboard while using a mixture of rice straw and wood particles is to add 30% rice straw to the mixture, use 11% melamine urea formaldehyde resin and employ a pressing time of 4 minutes.