فصلنامه پژوهشهای علوم و فناوری چوب و جنگل
سال هجدهم شماره 3 (پاییز 1390)

The kinetics of the delignification at the residual phase of kraft pulping of bagasse was studied. Kraft pulping was carried out under chemical charge of %14.11 (as NaOH, based on O.D. bagasse), sulfidity of %25.11 and liquor to raw material ratio as 20: 1. The cooking maximum temperatures as 85, 70 and 55°C, were selected and reaction time varied from 0 to 720 min. based on maximum temperature. The initial Klason and acid soluble lignin content of bagaase were measured as %19.23 and %1.87, respectively. The rate of delignification was first order with respect to lignin yield based on oven dried raw material and the process at least can be divided into three delignification phases. The reaction rate constants of delignification varied with pulping maximum temperature. The values were 1.6×10-3 min-1, 1.5×10-3 min -1 and 1.4×10-3 min-1 for cooking maximum temperature of 85, 70 and 55°C, respectively. The activation energy of delignification was 4.27 kJ/mol for residual phases. Lignin content at the transition point of second and third phases was calculated as 4.66, 5.21 and 6.17 percent for the cooking times of 85, 70 and 55oC, respectively. Thus, at transition points, lignin content of the pulp is a function of pulping temperature and decreases with increasing of cooking temperature.

Unbleached kraft pulp of Eucalyptus microtheca from Iranshahr region (Sistan and Baloochestan province) was prepared and its physical, mechanical and optical properties including grammage, thickness, density, bulk, tensile strength, tear strength, burst strength, brightness and opacity, were measured. To determine the best experimental treatment concerning total mechanical and optical properties of handsheets, the scoring method based on the normalization equations was used. The mechanical and optical properties of the best treatment were determined as follow: Tensile index 40.50Nm/g, Tear index 5.68 mNm2/g, Burst index 2.954 kPam2/g, Brightness 17.77 percent ISO and opacity 98.57 percent. The results show that unbleached kraft pulp of Eucalyptus microtheca from Iranshahr has suitable mechanical and optical properties for the production of packaging paper. Thus, development of its plantation in Iranshahr region, with the aim of supplying part of the required cellulosic raw material for local pulp and paper industries, is recommended.

In this research, the sanding dust was used to manufacture wood –plastic composite its their properties were compared with wood flour–Polypropylene composite. Sanding dust and wood flour were separately mixed with of Polypropylene at three levels of 50%, 60% and 70%. Coupling agent (MAPP) was used at two levels (4% and 6%). Totally twelve composites were produced. The composites were manufactured using hot press. After preparation of test samples, mechanical properties (bending and hardness) and physical properties (water absorption and thickness swelling) were measured. Results showed that addition of both fillers reduced modulus of rupture and increased modulus of elasticity, water absorption and thickness swelling. The urea – formaldehyde resin present in sanding dust caused a reduction in mechanical and physical properties of polypropylene-sanding dust composite compared with polypropylene -wood flour composite at the same levels of fillers.

In this research, the decay resistance of sawdust–polypropylene composite has been evaluated by microscope. The scope of research was to assess the effect of different weight percentages of sawdust (45%, 60% and 75%) sawdust distribution on the fungal decay. ASTM D1413-99 test method was used to carry out decay test and Trametes versicolor was chosen as a white rot fungus. After 12 weeks exposure of the composites samples to the fungi, the weight losses were determind using Soil Block test. Analyzing the data using ANOVA one way statistical method, it has been shown that the weight losses of the composite due to decay were proportional to the sawdust weight percentages. Also, it was found that weight losses were higher in those treatments with upper sawdust percentages. In order to microscopic study, a light microscope was used. The results showed that increasing in the weight percentage of sawdust, led to particles aggregation, their nonuniform dispersion, decreasing in particles encapsulating by polymer and increasing in hollows and voids between sawdust and polypropylene which made the composite susceptible for fungi attack.

In temperate forests canopy gaps play an important role in driving stand dynamics. The purpose of this research was to compare soil characteristics in forest gaps with several size and its relation to Beech regeneration density in Lalis forest, Chalous. In order to investigate factors, three gap sizes as small gap (200 m2), medium gap (400 m2), and large gap (600 m2) with three replicate were selected in locatation. Mineral soil samples were randomly collected from four different places in each gap, all over the gap area. Nine circular subplots of 3.14 m2 were established inside each gap on two principal diagonals and the regeneration density of Beech species was estimated. Some of soil characteristics, such as total carbon, total nitrogen, available phosphorous, soil acidity (pH), C/N ratio, saturation moisture and soil texture (clay, silt and sand) were measured. Results showed that the carbon and C/N ratio significantly decreased with increasing of gap size. The other soil characteristics significantly increased with increasing of gap size. Similar to results, statistical difference between regeneration densities with soil characteristics was found. With thicken of soil characteristics consisting of nitrogen, phosphorous, pH, and moisture, regeneration density increased. Carbon and C/N ratio affected negatively on regeneration density, But there were no significant differences in soil texture ingredient between gaps.

Tree bark has an important role in cambium protection, vital activities and defences against disease and insects. Determination of bark is important for estimating wood volume and tree growth. The trading of forest woods is based on tree volume that include bark, thus, knowledge of bark percentage of forest trees is important. The purpose of this study is to examine the variables affecting bark thickness and to derive models predicting bark thickness of standing tree in Asalem forest area.Totally, 179 beech trees (Fagus orientals Lipsky) were measured based on diameter classes (5 cm). The results showed that bark thickness is affected by different variables including diameter, total height and age of trees. Bark thickness in varied diameters is different, so that, the percentage rate of bark in class with diameter lower than 40 centimeter to the class with a diameter 40 to 80 centimeter and a diameter over 80 centimeter is 1.2 and 1.49, respectively. The results of this study indicate that the bark percentage in trees with fewer diameters is higher than in thicker trees. However, the amount of bark thickness increases with increasing of tree diameter, and the correlation between tree diameter and bark thickness is positive, with a R2 of 0.72. The amount of bark thickness increases as tree age increases as well, and the percentage rate of bark in class with age lower than 80 years to the class with a age 80 to 150 years and a age over 150 years is 1.12 and 1.41, respectively (R2=0.67). In order to create suitable model for estimating of bark thickness, 10 statistical models were tested by regression analysis. Power model with coefficient of determination of 0.84 (R2=0.84, See=0.221) is suitable for estimating of bark thickness for Fagus orientals Lipsky.

Reinforcing the medium density fiberboard with metal and synthetic nets was the main object of the present study to enhance is mechanical properties. Sample boards were manufactured by routine processes. Two types of the reinforcements, steel metal and synthetic nets, were applied in both surfaces of the sample boards. The reinforcements were placed 1/4 of the board thickness, adjacent to the surface layers. Urea formaldehyde resin was applied in the boards. However, a group of the metal reinforcements was embedded in epoxy resin prior to application in the boards. Bending strength of the boards were determined according to DIN EN 310 and the value of modulus of elasticity. Results revealed that the reinforcements affected the bending properties in the boards. The boards reinforced with the metal nets gained higher strengths than the synthetic ones. Application of the epoxy embedded reinforcements caused the boards to achieve the highest strengths than the others.

In the present research, kenaf chips have been pre-extracted to weight loss levels of about 8.5, 11.5 and 14.5%, based on oven dried Kenaf chips by hot water and acid catalyzed hot water prior to pulping process. Pre-extracted and un-pretreated (control sample) Kenaf chips were converted to pulp by soda-AQ process at three cooking times 60, 90 and 120 minutes. The results of pre-extraction stage indicated that pre-extraction time to achieve a specified weight loss has been reduced with addition acid catalysis (Sulphric Acid). The results of pulping indicated that pulp yield reduced by increasing cooking time as well as weight loss of Kenaf chips in pre-extraction stage. In terms of the average pulp yield and kappa number at constant cooking time, there were significant differences at 1% error level between un-extracted (control sample) and the chips pre-extracted to 8.5, 11.5 and 14.5% weight loss. As, control pulp had highest yield and kappa number and pre-extracted pulp, at 14.5% weight loss, had lowest yield. In addition, in terms of pulp yield there were significant differences at 1% error level between un-preextracted (control) Kenaf chips and samples extracted with pure hot water and acid catalyzed hot water at any weight loss levels of 8.5, 11.5 and 14.5%. Control pulp had highest and hot water pre-extracted pulp had lowest yield. Significant differences at 1% error level were observed between control sample and pre-extracted Kenaf chips at similar amounts of weight loss in terms of average pulp kappa but there were no significant differences for average kappa number between pulps pre-extracted from hot water and acid catalyzed treatments. The results of physical and strength properties of hand sheets showed that different strength amounts were reduced by increasing the amounts of pre-extracted weight loss from 8.5 to 14.5% for all second pre-extraction methods. On the other hands, strength amounts of pulp from hot water pre-extracted Kenaf chips were often lower than pulp samples pre-extracted by acid catalyzed hot water.

Suitable site-selection of industrial units creates proper conditions for optimum use of material and reduction of waste, and on the other hand, leads to more sell and hence high profit. The objective of this study is to determine the effective criteria in decision making of selecting the most suitable location for establishing a furniture unit. For this purpose, after preliminary investigation and interviews, 25 effective criteria were identified. The hierarchy of these criteria was designed and then the priority rates (weighting value) of obtained criteria and sub-criteria were determined using Analytical Hierarchy Process (AHP). The results showed that among 25 identified effective criteria, the five criteria as market capacity, purchasing cost of raw material, man force availability, granted facilities and man force cost have the highest priorities, respectively.

Regarding to various applications and adequate characteristics of HPL veneer such as beauty, mechanical strengh, un-absorption of water and vapor, as well as chemical and thermal resistances, the need to this veneer has been developed in different industries and local production make possible exchange saving. Therefore, investigating the effective criteria on optimal site-locating of HPL veneer factories has been important. For this study, the Golestan province was selected as one of talented provinces in wood industry. The effective criteria on HPL veneer site-location has been recognized and classified into "Economics", "Substructure", "Humanity" and "Materials and product" groups. The survey data has been gathered from experts, industry holders and academic connoisseurs in 2009. Weighting and ranking of measures has been conducted using flexible and practical AHP technique and the Expert Choice software. The results revealed that among 23 investigated effective criteria for site selection of HPL veneer the score of factories, the status of lateral industries with the score of 0.115, high capacity of investment absorption (0.095), number of competitors and sale markets (0.088), and assurance in supplying raw materials (0.071) were selected as priorities. By the way, the weights of materials-product, substructure, economic, and humanity criteria were derived as 0.339, 0.283, 0.268 and 0.110, respectively.

To determine of biometrical (fiber length, fiber diameter, lumen and cell wall thickness), physical (density and volumetric swelling), chemical (amount of extractives, cellulose, lignin and ash) and mechanical (modulus of rupture, modulus of elasticity, compression strength parallel to grain, compression strength perpendicular to grain, shear parallel to grain, janka-hardness and nail withdrawal) properties of eucalyptus camaldulensis wood from Sistan region five trees were selected and evaluated. The results showed that fiber dimensions in tree trunk, from pith to bark and decreased from bottom to top. The volumetric swelling variation decreased in radial axis from pith to bark and in longitudinal axis from bottom to the top. There were no significant different at 5 percent statistical error level between the cellulose and ash content values in heartwood and sapwood, respectively. On the other hand, significant difference at 5 percent statistical error level was observed between lignin and extractives values in heartwood and sapwood, respectively. Also, mechanical properties of wet and dry samples were determined. The results indicated that the mechanical properties of wet samples were lower than dry samples, significantly.

Alkaline sulfite pulping of old corrugated container to produce bleachable pulp was investigated. Pulping variables including active alkali of 14, 16, and 18% (based on oven-dry weight of OCC and Na2O); sodium sulfite to sodium hydroxide ratios of 50:50 and 30:70; pulping temperatures of 125,145,165 and 175ºC and pulping time of 60 and 120 minutes were examined. After preliminary pulping and evaluation of the strength of the pulps with the lowest kappa number, pulp with kappa number of 18.3 and brightness of 50.17% which was produced applying 18% active alkali, sodium sulfite to sodium hydroxide ratio of 30:70 and pulping time and temperature of 120 minutes and 175ºC respectively with 64% yield (based on oven dry weight of washed OCC) and 72.7% yield (based on original weight of the OCC) was selected for totally chlorine free bleaching trials. Brightness, opacity, tensile and tear strength indices of this pulp were measured as 50.17%, 81.36%, 27.7 N.m/g and 12.35mN.m2/g, respectively. Bleaching this pulp applying 3% H2O2 and 2.25% NaOH generated bleached pulp with brightness and opacity as 57.14% and 78.24%, respectively. The bleaching yield was measured as 92%. Tensile and tear strength indices of this pulp were measured as 27 N.m/g and 12.45 mN.m2, respectively.

Structural investigation of different parts of raw material is a step to achieve its more suitable processing. The aim of this study was to investigate fiber morphology and chemical composition of rice straw parts at different heights for internodes in lower, middle and upper parts, leaves and nodes separately as wella their mixture. Fibers were separated using Franklin method and their chemical composition was determined according to the related TAPPI test methods. Results showed that fiber length, fiber diameter and cell wall thickness of fiber decreased in internodes from down to top. The largest diameter and cell wall thickness were related to the nodes. The amounts of ash, acetone extractable materials, lignin and cellulose of leaf were higher than the other parts of the straw. Ash and acetone extractable materials percentage increased in straw from down to top but amounts of lignin and cellulose decreased in straw in the same direction. The results indicate that the internodes of rice straw are better than the leaves for pulping because of the average longer fibers and lower percentage of extractive, ash and lignin in internodes than the levels. So, in preparation of the pulp raw materials, it is necessary to remove the unsuitable parts of rice straw such as leaves and nodes.