مجله تحقیقات علوم چوب و کاغذ ایران
سال بیست و ششم شماره 3 (پیاپی 36، پاییز 1390)

In this study, the effect of elimination and relative decrease of sodium silicate along with substituting the organic complex of sulvy-x was investigated on optical properties of CMP pulp bleached by hydrogen peroxide. The brightness of paper were increased to 66.8%, yellowness decreased to 22% and opacity decreased to 80% with increase in sodium silicate charge from 0.7% to 3%. Also, with complete elimination of sodium silicate and using of sulvy-x at different levels of 0.4, 0.5, 0.7 and 1%, highest brightness and lowest yellowness were shown at 0.5% sulvy-x. These values were 66.1% and 21.8%, respectively. The brightness of paper enhanced from 61.2% to 67.3% with increasing of sulvy-x charge from 0.4% up to 0.5% blended with constant value of 0.7% sodium silicate. But the brightness decreased at higher levels. Generally, pretreatment by DTPA prepared the paper with lower brightness and higher yellowness at two different states namely silicate-free and silicate-containing with sulvy-x. Pretreatment by DTPA at silicate-free state led to decrease of opacity but at silicate-containing state terminated to improve of opacity values. Increasing of bleaching time up to 120 minutes resulted in the paper with higher brightness, higher opacity and lower yellowness at silicate containing state with sulvy-x. At silicate-free state, increasing of bleaching time up to 120 minutes led to improve of opacity while brightness improved and yellowness reduced with increase in bleaching time to 90 minutes. Also, the brightness of paper decreased at higher times (120 minutes) and yellowness increased. In conclusion, achieved results from comparison of optical properties of paper produced from peroxide bleaching of hardwood CMP pulp indicated that we could produce the paper with desirable or even better optical properties by replacing of sulvy-x rather than sodium silicate compared to conventional peroxide bleaching.

This research was performed to investigate the properties of CMP pulp from rape straw. Samples of Colza straw was prepared from a farm located in the vicinity of Babul. Chemo mechanical Pulping process was employed using the 20 % cooking liquor of Mazandaran pulp and paper mill (Sodium Sulphite) based on the dry weight of colza straw. Cooking time and temperature were adjusted at 30, 40 and 50 minute and 170 degree centigrade, respectively. Pulps were refined up to 300± 25 CSF by using PFI Mill refiner and 60 g/m2 hand sheets were made from each sample of pulps. The strength indices of hand sheets were measured using TAPPI standards. The results showed that strength indices like Tensile strength, Tear strength, Burst strength, Breaking length and Stiffness increased as the pulp yield decreased.

In the present study the effects of hot water pre-extraction and alkaline catalyzed were evaluated on soda-aq pulping of kenaf whole stem. In this respect, following kenaf chips pre-extraction at various temperature and time conditions, pulp preparation were carried out on oven-dried weight loss levels of 8.5, 11.5 and 14.5 % of the samples, and the reference untreated kenaf chips performed by using Soda-AQ at 3 levels of H-factors (983, 1408 and 1832 hours). Results indicated that kenaf chips weight losses increased while the pre-extracted pH decreased as pre-extraction temperature and time increased. The required H-factor for achieving certain level of weight loss was reduced by adding small amounts of alkali (0.15 % on oven dried kenaf) on hot water extraction stage. The Pulp yields were reduced by increasing cooking H-factor and extracted weight loss. Averages comparison indicated that significant differences were observed, at 95% confidence, between the pulp yield and kappa number from reference pulp and pre-extracted pulp samples at levels of about 8.5, 11.5 and 14.5 %, and pulp yields and their kappa number were higher in reference pulps than pre-extracted samples. In addition, pulp yield average was higher in pre-extracted samples by alkaline catalyzed than pre-extracted samples by hot water, however, no significant differences were observed between their kappa number average. Meanwhile, to obtain a certain (similar) kappa number, pre-extracted kenaf chips in comparison with reference untreated kenaf chips require lower H-factor.

Effect of Kraft lignin as a compatibilizer on the short-term water absorption (2 and 24 hours) and mechanical properties of wood flour-polypropylene composites was studied. The black liquor of Chooka pulp and paper mill was acidified and Kraft lignin was extracted by precipitation. The extracted lignin at three levels of 2, 5 and 10 percent was mixed with wood flour by physical mixing method. All materials used were oven-dried. Wood flour, lignin and PP with or without MAPP were used to produce composites by flat hot press method. The results of this study indicated that generally lignin improved physical (short term water absorption) and mechanical properties (flexural modulus, flexural strength and impact strength). The bending test result showed that without MAPP, the composites with 2 and 10 percent lignin exhibited higher flexural modulus and strength, respectively. But at the presence of compatibilizer, the composites with 5 percent lignin exhibited the highest flexural modulus and strength. The composite with 2 percent of lignin exhibited higher flexural modulus and short-term water absorption rather than the composites with 2% MAPP. This result indicated positive effect of lignin in the composites. Also the composites with 10 percent lignin exhibited the highest impact strength and short-term water absorption. But there were no significant difference between the impact strength of composites with 5 and 10 percent lignin.

This research was conducted to evaluate the effects of acetylation and the resin type on three layered populus particleboard against white-rot fungus, Trametes versicolor. Populus particles were acetylated at three levels of acetyl content (WPG of 0, 8.39% and 17.27%). In manufacturing of single and three layered boards with acetylated particles two type of resin, urea formaldehyde and isocyanate(as adhesives) were employed. The results indicated positive role of acetylation in reducing decay rate. Weight loss of boards made from isocyanate was less than the boards containing urea formaldehyde resin. Also, three layered boards showed higher resistance against the fungus compared with single layered boards.

The longitudinal gas permeability of tension wood and normal wood of Populus nigra dried by two different drying conditions was measured. Board specimens were dried under mild conditions (50ºC, and ٪63 relative humidity) to reach ٪11. 8 MC, and under severe conditions (62ºC, and ٪35 RH) to reach ٪7 MC. After drying, dowel specimens of 14 mm in diameter and 40 mm length were prepared. Epoxy resin was applied all around each specimen to prevent fluid passing through lateral direction. Results showed that under both moisture conditions, longitudinal gas permeability values in normal wood were greater than those in tension wood. Furthermore, the permeability of both tension and normal wood decreased by increasing of drying intensity and decreasing of final moisture content.

In this study two types of paper sludge, prepared by Mazandaran wood and paper company and Latif papermaking company along with wood flour utilized as plastic filler in polypropylene and high density polyethylene based composites. Weight percentage ratio of coupling agent, polymer and filler were kept constant 2%, 38%, and 60% in all formulations, respectively and composites were prepared by varied ratios of paper sludge and wood flour include 0: 60, 40: 20, 20: 40, and 60:0. Density, water absorption and thickness swelling of injection molded composites then measured. The results indicated the gradual substitution of wood flour by paper sludge increases the density of composites, and improves their water absorption and thickness swelling. The ratio of paper sludge to wood flour had statistically significant difference on all these properties, but the paper sludge type showed statistical difference just on the density of composites. Further to that, polypropylene based composites demonstrated lower density, water absorption and thickness swelling compared to high density polyethylene based ones.

Utilization of date palm and kenaf fibers for reinforcement of plywood was investigated and after making plywood with layers of horn beam wood (Carpinus betulus), physical and mechanical properties were analyzed. Variables were the type of fiber (kenaf and date palm), the type of filler (wheat flour and waste paper) and the content of resin (150 and 200 g/m2). The results of this study show that utilization of kenaf and date palm fibers was effective in improvement of physical and mechanical properties of plywood. The mean of specific gravity for reinforced plywood with kenaf and date palm fibers was 0.723 and 0.739 g/cm3 respectively and specific gravity of control was 0.656 g/cm3. The least water absorption and thickness swelling were about reinforced boards with kenaf fibers and 200 g/m2 resin with wheat flour filler. The reinforced boards with kenaf fibers and 150g/m2 resin with wheat flour filler have the best mechanical properties. So the kenaf fibers for reinforcement of properties of plywood were better than date palm fibers and the utilization of wheat flour in manufacture of these boards had better results compared to waste paper filler.

The purpose of this study was to investigate which equation (Linear, Exponential equation and quadratic) can describe exactly the interaction effect of particle size and adhesive percent and predict mechanical properties of particleboard (modulus of rupture, modulus of elasticity and bending strength). For this work three levels of density including 0.65, 0.7, and 0.75 g/cm3 and also, three levels of adhesive content including 8, 9.5, and 11% and four levels of slenderness ratio of particles including 46.35, 33.7, 21.51 and 12.87 were used. After conducting the experiment and preparing the data, three kind of equation (linear, quadratic and Exponential equation) for each mechanical property based on slenderness of particles, density and adhesive percent obtained. The result indicated there was no correlation between mechanical properties of particleboard and quadratic equation but there were good correlations between linear and Exponential equation. Also the result indicated that Exponential equation can describe efficiently the simultaneous effect of slenderness and adhesive present on the mechanical properties of particleboard, and it can predict better mechanical properties than linear equation.

In this research, effects of mixing the birch wood with hornbeam and beach on optical and physical properties of papers produced at constant freeness range of 300 ml, CSF and yield of 85% and reference of CMP pulp (75% hornbeam plus to 25% beach) was investigated. CMP pulp was produced from birch chips at 10,20,30 and 40% content within the conditions of pulp yield:85%, liquor to dried chip ratio (L/W) of 7/1, sulfite percent of 20% on oven-dried wood chips, cooking temperature:160C, cooking time:85-135 minutes blended with 60-90 % hornbeam and beach. After defibration and refining the cooked wood chips, the standard hand sheets of 60 g/m2 were made from different pulps and the optical and physical properties of paper produced were compared. The results from comparing the optical properties of paper showed that using up to 40% birch chips blended with hornbeam and beach led to brightness improvement and yellowness and opacity reduction compared to control CMP pulp. Increase of birch use to 30% indicated no significant effect on opacity values at confidence level of 99% compared to control CMP pulp. Utilizing 40% birch resulted in the preparation of papers with lower caliper, smoother surface and higher air resistance.

This research was performed to investigate fiber biometrical properties (length, diameter and fiber thickness) of hornbeam species from Astara in Iran. Initially, disks were prepared with three trees of hornbeam species and then fiber isolation was carried out using Franklin method. Length, diameter and wall thickness of fiber provided were determined by laboratory microscope using eye scaled lens. The measurement of fiber dimensions was made at the pith region and at the distances of 2,6,12 and 15 centimeters and four geographical sides. The results indicated that length, diameter and wall thickness of fiber increased significantly with enhance of distance from pith. The highest fiber length, diameter and wall thickness obtained were 1.509 mm, 23.93 µm and 3.897 µm, respectively. The consequences attained from changing of fiber dimensions at various distances from pith to bark indicated that fiber dimensions change decreased by increase in distance from pith up to 15 cm and the highest change of fiber was observed at distance of 2-6 cm from pith. The results of measuring the fiber dimensions at various geographical sides didnt indicate any significant deference between the values of fiber length, diameter and wall thickness at 1% level of probability. The combined effects of distance from pith and different geographical sides also did not show any significant deference on fiber dimensions.

Paper’s components identification is important for pulp and paper mills and many organizations. In the present study we tried to identify paper fibers and introduce the most important anatomical characteristics which are effective in identification. First anatomical characteristics of wood and non-wood species which are important in pulp and paper industry were investigated. Then the papers of 3 important paper mills in Iran (totally 5 different papers) which their raw material include forest species, imported pulp and waste paper were sampled and examined. Many slides have been prepared according to ISO 9184-1 (ISO 1990) standard and valuable Atlases useful for identification of exotic species were reviewed. At the end important anatomical characteristics were recorded. Results showed that the fiber identification of papers is feasible. For softwoods identification, cross-field pits and for hardwoods, vessel shape, including, spiral thickening, perforation plate, inter-vessel pits and especially ray- vessels pits are the most crucial features for identification. Parenchyma, fiber biometric properties and fiber shape, in most species were similar and least effective in identification process. Epidermal cells, parenchyma and vessels were the most important anatomical feature for identification of non-woods.

In this investigation, anatomical characteristics of Iranian native woods from Ulmaceae family: Ulmus glabra, Ulmus carpinifolia, Zelkova carpinifolia, Celtis australis have been compared. These 4 woods are similar and have been used in Iranian historical buildings and their identification would be important. Among 4 species, Zelkova carpinifolia is somehow similar to Celtis australis while, Ulmus glabrar is close to Ulmus carpinifolia. Boundary cells of rays in Zelkova carpinifolia and Celtis australis are bigger than inside cells of rays. The difference between Zelkova carpinifolia and Celtis australis are in ray width. Ray width of Celtis australis is 7-8 cells, whereas Zelkova carpinifolia 5- 6 cells. The color of soluble (Glycerin + water) which have been used for softening of wood samples (2× 2 cm) for Zelkova carpinifolia got golden color but others grey. The difference between Ulmus glabra and Ulmus carpinifolia are in appearance of rays. The appearance of Ulmus carpinifolia’s ray is short and wide while ray of Ulmus glabrar is tall and slender. Meanwhile the frequency of rays in cross section of Ulmus carpinifolia is 6-8 per millimeter but in the case of Ulmus glabrar the figure is 4-5.

In this study, the susceptibility of poplar (P. nigra) tension and normal wood to collapse during drying was investigated. Thus, the poplar boards with nominal dimensions of 100 × 50 × 25 mm (L×T×R) were dried using three different drying schedules. In schedule A, the boards were dried under constant conditions (dry-bulb temperature of 600C and wet-bulb temperature of 440C); in schedules B and C, they were dried under a time-based schedule, consisting of 4 and 2 steps, respectively. The initial dry-bulb temperature in schedules A, B and C were selected as 60, 60 and 820C, respectively. After drying, the severity of collapse in the cross section of boards was determined by scanning electron microscope (SEM). The results revealed that collapse did not occur in the boards dried by schedule A. Collapse occurred slightly in the boards dried by schedule B and severe collapse and cell wall degradation developed in the boards dried by schedule C. In the latter, gelatinous layer of tension wood was separated from fiber cell walls. Tension wood was more sensitive to collapse than normal wood. Based on the results, it can be concluded that the occurrence of collapse is influenced by initial dry-bulb temperature rather than wet-bulb depression.

In this paper effect of static densification of treated paulownia on relationship between strength properties and density was investigated. Specimens were steamed at 130 and 170oc and immediately were compressed to 35% and 45% of their original thickness in radial direction. Mechanical properties such as bending strength, brinell surface hardness and compression strength in axial and radial direction were determined for non-densified and densified wood. Indexes of density, strength, quality and strength potential were calculated to study the relationship between strength and density. The results show that the density index and strength index and also strengths significantly increased with increase in densification but strength potential indexes decreased. Steam treatment at 130oc had a slight positive effect on the strengths and strength potential indexes as effect of softening the wood but the strength potential indexes and strengths decreased due to treatment of wood at 170oc. Generally, strength potential indexes of all tested mechanical properties show that strength of densified paulownia was lower compared to what had expected for non-densified paulownia from increasing density, which in turn demonstrate the cell walls were negatively affected by compression. Axial compression strength and brinell hardness were slightly affected by densification.