مجله تحقیقات علوم چوب و کاغذ ایران
سال بیست و ششم شماره 1 (پیاپی 34، بهار 1389)

This research was conducted to investigate the feasibility of producing particleboards using surface activation method of P. deltoides particles followed using cross-linking agents to bond wood particles. At first, nitric acid was used as an oxidative agent at different proportions including 0, 3, 4.5 & 6 percent (based on OD weight of wood) and two assembly time of 0 and 1 hour. Black liquor was used as cross-linking agent at two amounts of 5 and 7 percent. The results indicates that using 6% nitric acid and 7% liquor had the best performance and that, the assembly time of 1 hour had negative effect on all properties. The ATR spectrum of treated samples showed the increase in the absorbtion rate at 1740 cm-1 related to COOH group as compared with control samples. The spectrum indicated that increasing oxidation, would increase absorbtion rate of COOH group aswell.

In this study, changes in optical behavior of poplar Kraft lignin and bagasse Soda lignin, before and after reducing with sodium borohydride and sodium hydrosulfite (dithionite) and also after methylation using dimethyl sulfate, was monitored by measuring optical indices (brightness, k/s, whiteness and Post-Color numbers) of impregnated papers following accelerated thermal aging. The structural changes in lignins caused by reductive reactions, were mostly verified by using absorbance changes (UV-Vis spectrometry) and FI-IR spectroscopy. It was observed that, regarding elimination of chromophoric carbonyl and quinone groups, sodium borohydride showed better and more sustainable performance than sodium hydrosulfite. Therefore, it could be inferred that to improve the brightness of lignin-containing papers and persistance of this brightness, sodium borohydride could exhibit more efficiency and higher applicability.

In this investigation, 36 laboratory medium density fiberboard (MDF) panels were produced using alder wood fibers. The variables were steaming time of 5, 10 and 15 minutes, press time of 4 and 6 minutes and resin content of 9 and 11%. Physical and mechanical properties of panels were measured and analyzed. The results indicated that the maximum MOR was related to panels produced with 6 minutes press time and 11% resin consumption. The maximum Internal Bonding (IB) was related to panels made with 15 minutes steaming and content resin of 11%. However, test panels produced at 6 minutes press time showed minimum thickness swelling. The results indicated that the MDF boards produced from alder wood fibers exhibit desirable physical & mechanical properties which are above then EN standards. Consequently application of alder wood fibers to improve physical & mechanical properties of MDF panels produced from nonwood materials and agricaltural residues is recommendeable.

Paper and ink characteristics effects on print density were investigated. For this purpose three types of papers and four types of printing inks at 2 viscosities levels (25-30, 50-55) were used. After measuring of paper and ink characteristics, chosen paper were Printed by inks and then printing density was measured. Statistical analysis was conducted based on a complete randomized design in factorial experimental model and means were analyzed and grouped by Duncan multiple range test (DMRT) using SPSS software. Result indicated that solid content, pH and particles diameter of inks have significant effect on print density. While roughness and water absorption of papers do not have on significantly influences on print density. There was not any significant difference between two viscosity levels and print density.

In this study, particleboard was produced by eucalypt and poplar wood mixture. Variations were as follow: -Combinations of Eucalyptus and Poplar wood were (%100, %0), (%66.5, % 33.5), (%33.5, % 66.5) and (%0, % 100) respectively. -Resin content (%8 and %10) Physical and mechanical properties of boards such as MOR, MOE, IB, TS2 and TS24 were examined according to EN standard. The effects of various raw materials combinations on bending properties were significantly different. Maximum of MOE and MOR were observed in %66.5 of Poplar wood and % 33.5 of Eucalyptus wood. As expected, Physical and mechanical properties of boards were improved by increasing of resin content. Results indicated that TS2 and TS24 were increased with increasing of Poplar wood in combinations. Also the lowest amounts of these properties were obtained in eucalyptus and poplar wood mixture of %100 and %0 respectively.

Bagasse pulping process was conducted using soda liquor in five maximum cooking temperatures, 80, 100, 120, 140 and 160 degree centigrade. To evaluate rate equations of delignification reaction in each temperature, pulping was done in the same alkali and liquor to bagasse ratio but varying cooking times and the results were presented in the form of rate equations with respect to residual lignin concentration in the pulp. The rate equations revealed that delignification reaction rate of bagasse depends both on cooking temperature and residual lignin concentration. The order of rate equation in higher temperatures is far higher than those in low temperatures and due to this, reaction rate in high temperatures is more dependent on residual lignin concentration and far than the rate reaction in lower temperatures. With reaction progressing, the difference between the two rate reactions is reduced and after one point it will be reversed. Using experimental data, the order of delignification reaction rate in temperatures 80, 100, 120, 140 and 160ْ C were obtained as 4. 6, 4. 6, 5. 5, 22. 8 and 22. 7 respectively. The rate constants were also calculated as 1. 3×10-5 conc. -3. 6 min. -1, 1. 1×10-4 conc. -3. 6 min. -1, 7. 2×10-5 conc. -4. 5 min. -1, 6. 2×10-10 conc. -21. 8 min. -1, 4. 0×10-11 conc. -21. 7 min. -1, respectively.

In this research pulp and paper making characteristics of Sequoia sempervirens from Chamestan noor research station were studied. The dry and critical specific gravity of sap wood 0.352 and 0.324, heart wood 0.43 and 0.40, fiber length 2.01 mm. diameter 39.84µm. lumen 33.15µm and cell thickness wall 2.89µm. The amount of cellulose, lignin, extractive and ash were measured as 52.63%, 35.32%, 6.68% and 0.45% respectively. Kraft process was used for pulping. The yield of these pulps in 12% effective alkali were obtained as 56% and in 18% effective alkali 39.69% respectively. The tear strength of these pulps In 3 and 2 hours cooking times were measured as 19.74 mNm2/gr and 15.22 mNm2/gr respectively.

This study was conducted to investigate the properties of APMP pulp. Prepared from chipped cotton stalks. The pulps were prepared separately from debarked and bark containing stalks using three two-stage treatments.Sodium hydroxide charge as a constant level of 4% and hydrogen peroxide at three levels of 0, 1 and 2% were used in to two-stages, sodium hydroxide as a constant level of 2% and hydrogen peroxide at three levels of 2, 3, 4% were applied. Other conditions of pulping was time's of 20 min for first stage and 100 min for second stage, temperature 70°C and l/w:6:1 as fixed factors considered. Pulp yield determined after neutralization and defiberation. All the pulps were refined up to 300 (ml, CSF) freeness and handsheets were made, then and properties of papers measured using TAPPI standards. Results showed that the pulp yield and brightness was higher in free-bark compared to bark-containing conditions. Also paper produced in free-bark condition with cotton stalks core, resulted the higher tensile and burst indexes and higher breaking length compared to whole cotton stalk.While tear index didn’t show significant difference.Generally, caliper and bulk rates were high in total treatments (free-bark and bark-containing conditions) from cotton stalk APMP process.

In this study, the effect of organic complex "sulvy-x" on the optical properties of hornbeam CMP pulp bleached with hydrogen peroxide was investigated. Sulvy-x was used in two sequences silicate-free and silicate containing in hydrogen peroxide bleaching. The brightness of papers increased to 60.52 while yellowness decreased to 22.6 with increasing silicate charges up to 1%. However, at higher levels than 1%, the brightness decreased and the yellowness increased. Without dosage of sodium silicate but using 0.5% of sulvy-x, maximum brightness of 59.3% and minimum yellowness of 23.4 % ISO was achieved. In silicate-containing bleaching, combination of 0.5% sulvy-x and 0.7% sodium silicate resulted in the highest brightness (60.28 % ISO) and the lowest yellowness (23 % ISO). Optimum charge of sodium hydroxide and hydrogen peroxide were determined as 2.5% and 5%.The best time for bleaching of hornbeam CMP pulp was 90 minutes in either sequences. With regard to results obtained, utilization of the organic complex of sulvy-x could be a suitable substitution for sodium silicate which produces the pulp with higher brightness and lower yellowness in conventional peroxide bleaching.

The objective of this study was to investigate the effect of aminosilane coupling agent on properties of UF and MF-bonded wheat straw boards. The hydrolyzed silane coupling agent was sprayed on fine particles of wheat straw, and blended with UF and MF resins to produce the straw boards. The results showed that the aminosilane had significant effect on improvement of physical and mechanical properties of straw boards so that the internal bond strength was increased significantly by adding the aminosilane up to 2% and 5%. Also thickness swelling significantly decreased at up to 2% silane content, but significant effect was not observed at above 2%. The high-property boards could be contributed to the improvement of bondability between particles and resins for the surface treatment of wheat straw particles by silane coupling agent. The aminosilane had no significant effect on bending strength whereas the bending strength and thickness swelling of MF-bonded boards were improved significantly, because of higher amine groups in melamine formaldehyde resin compared to urea formaldehyde resin.

In this study, aspen chips with OCC (Old Corrugated Container) were used in particleboard production and samples were prepared at two different levels of resin contents (%9 and %10) and three levels of combination: 1- %25 OCC +%75 aspen, 2- %50 OCC + %50 aspen, 3- %75 OCC +%25 aspen. Indeed in this study these two mentioned factors are variable and other factors such as press temperature: 165 ºC, press time: 5 minute, mat moisture %12, board density 0.75 g/cm3 and press pressure 30 kg/cm2 were constant. After the board's fabrication according to DIN-68763 standard, different tests were undergone include: bending strength, modulus of elasticity, internal bonding strength and thickness swelling after 2 & 24 hours immersion in water. The results indicate that second ratio(%50 OCC and %50 aspen chips) is proper for bending applications and the first ratio(%25 OCC and %75 aspen chips) is proper for tensile and thickness swelling applications. Therefore, applying the OCC more than %50 in manufacturing combination; result in decreasing the physical and mechanical properties. Moreover the results show that when the resin content increases, the board features improve.

The aim of this study was to determine effect of coupling agent contents on the thermal properties and nanoclay dispersion of reed flour /polypropylene /nanoclay composites. For this purpose we considered wood flour 40% fixed maleic anhydride in two levels (5% and 10%) and nanoclay (Cloisite 10A) in three levels (0, 1 and 3%). The materials were mixed in an internal mixer with 175 oC, 60 rmp for 10 minutes and then the specimens were fabricated by injection molding method. The clay structure and dispersion processes have been studied by X-ray diffraction. Thermal characterizations of the nanocomposites were carried out using Differential Scanning Calorimeter (DSC). The results revealed that Enthalpy, Crystallinity and Crystalline temperature of composites were increased by adding up of coupling agent and nanoclay (in some levels) contents. The XRD patterns show the exfoliation structure of nanoclay that indicated on a good dispersion of clay in polymer matrix, which in turn is a reason for increasing thermal properties.

This research was carried out to study the effect of Enzymatic deinking on strength properties of old newspaper deinked pulps. In order to perform this research, we did pulping operation with cellulase and lipase enzyme, in 4% consistency for 2.5 minutes in neutral PH, in two temperatures of 20 oC and 50 oC. Following pulp preparation, we started deinking process by washing on the 120 meshes. We did statistical analyses on the effect of enzymatic and temperature repairs on mechanical strengths of handsheets. The results showed that the enzymatic treatment increases the mechanical strengths of the treated pulps compared to the control pulp. Also, combined effects of cellulase and lipase on improvement of mechanical strengths of pulp were more than cellulase treatment alone. For handsheets made from control pulp the values of burst index, tear index, tensile index, breaking length and tensile stiffness were 1/43, 5/33 (mN.m2/g), 48/64 (Nm/g), 4/9 (km), 476/46 (kN/m), respectively. On the contrary, for enzyme treated pulps the optimum values were 1/92, 5/96 (mN.m2/g), 63/29 (Nm/g), 6/45 (km) and 584/31 (kN/m), respectively. This investigation showed that due to limited availability of woods, enzymatic deinking can be a suitable alternative instead of current deinking in paper recycling industries.

This experiment investigated the effect of the white and brown rot fungi on the PP-Bagasse fiber composites over 5 repetitions and 3 treatments during 8, 12 and 16 weeks. This product that is recyclable, have been made in the Alborz Research Complex under the laboratorial condition using the flat press method, 40% Bagasse fiber, 60% PP and 2%MAPP. At the end of experiment, the effect of nail was considered according to The mycelium coverage percent and Willitnear criteria. Also samples weight reduction and its stiffness was determined according to the standard of, ASTM1037.The samples after being cultured put into the kolle vessels, then they transferred to the incubator with the temperature of 23/5 and relative moisture of 75% and for reaching to the results, after each treatment, the necessary measurements was done. The first factor that evaluated was the mycelium coverage percent that was somehow less in white rot fungus in 8 compare to weeks brown rot fungi. After 12 and 16 weeks all the samples became 100 % covered with Mycelium. Finally the level of decay and the effect of Nail evaluated according to willitnear criteria in which the apparent decay in the brown rot was less than white rot. The weight reduction percent in samples being near in the white rot were more and after 8, 12 and 16 week this was significantly different. By using Sanatam device which is special for the resistant measurement of wood- plastic composite, the stiffness reduction was determined. The results showed that the level of stiffness reduction in the sample’s exposing to the white rot fungi were higher than those that were exposed to brown rot fungi.

This research was performed to investigate replacement of organic complex of Glanapone Stab with sodium silicate on optical properties of hardwood CMP pulp bleached by hydrogen peroxide. The highest brightness of 65.5% and the lowest yellowness of 21.6% was attained at silicate-free followed by replacement of 0.7% and 1.5% Glanapone. But the highest opacity 98.2% was gained using 0.5% glanapone. The brightness of paper increased to 68.1% and the yellowness decreased to 20.8. by adding of glanapone consumption from 0.4% to 0.5% in blended with 0.7% sodium silicate. At higher levels than 0.5% glanapone, the brightness of paper decreased and the yellowness increased. Using Higher levels of 1 and 1.5% glanapone in blended with 0.7% sodium silicate resulted the highest opacity 97.9% and 98%, respectively. Increasing of peroxide usage up to 5% at two different states of silicate-free and silicate-containing with glanapone resulted in the paper with higher brightness and lower yellowness and opacity. CMP pulps bleached at 120 minutes resulted the highest brightness of 71.1% and the lowest yellowness of 18.3% at silicate-containing state with glanapone. Maximum opacity of 98.3% and 98% were shown at bleaching time 30 minutes at two states silicate-free and silicate-containing state with glanapone, respectively. In this research with regard to optical properties in relation to paper produced from CMP pulp bleaching at two states silicate-free and silicate-containing with glanapone,it can be said that possibility of producing the paper with similar optical properties or even better using 0.7% or 1.5% at silicate-free is in compared to conventional hydrogen peroxide bleaching. Also, we could produce the paper with higher brightness along with lower yellowness and similar opacity followed by bleaching time of 120 minutes and hydrogen peroxide 5% in combination of 0.7% sodium silicate with 0.5% glanapone in compared to higher consumed values of sodium silicate.