مجله تحقیقات علوم چوب و کاغذ ایران
سال بیست و نهم شماره 3 (پیاپی 48، پاییز 1393)

In this study، optical behavior of methylated and unmethylated Bjorkman lignin from populus wood and two lignin model compounds (phenolic and non phenolic) with β-O-4 linkages after transferring on a cellulosic matrice (Whatman Paper) was investigated in different times (0، 5، 10، 15، 20 h). Then paper surface was analyzed using Attenuated Total Reflectance (FTIR) thecnique. The results showed that irradiation altered the chemical structure of all samples. Lignin was the most sensitive component to photodegradation and the intensities of its characteristic bands decreased significantly during the process of irradiation. This was accompanied by formation of new carbonyl groups appearing at 1735 cm_1. Compared with the unmethylated forms، the rate of lignin degradation and carbonyl formation was relatively lower in methylated forms. In other words، methylation of phenolic hydroxyl group reduced the chemical changes induced by irradiation.

In this study، cationic pulp fiber (CPF) was prepared and then was blended with virgin pulp fibers to produce handsheets and improve the paper properties. (3-chloro-2-hydroxy propyl) trimethyl ammonium chloride was applied in three levels of 0، 2، 4% (based on the OD weight of the fibers) to prepare cationic pulp fiber and three temperatures were used as follow: 40، 60 and 80 °C. The results showed that the effect of temperature، CHTMA and CHTMA*temperature interaction was significant statistically on cationizing the fibers. Maximum content of cationic CHTMA adsorption on pulp fibers was obtained by application of 2% CHTMA and 60 °C temperature with the average of 53. 33%. The mixture of 70% long fibers، 30% short fibers، 1% cationized pulp fiber، 5% PCC and three levels of C-PAM (0، 0. 05 and 0. 1%) was used to prepare handsheets. Freeness of blended pulp and mechanical properties of produced paper such as tensile index، tear index and burst index was determined. Statistical analysis of results showed that the effect of applied treatments was strongly significant on mentioned characteristics. The highest amount of CSF and mechanical properties obtained in different conditions as follow; freeness (669 ml): CPF 1%، C-PAM 0. 05%، PCC 5%; Tensile index (15. 25 N. m/g): CPF 1%، C-PAM 0. 1%، PCC 5%; Tear index (12. 3 mN. m2/g): CPF 1%، C-PAM 0. 1%، PCC 5%; Burst index (0. 68 kPa. m2/g): CPF 1%، C-PAM 0. 05%، PCC 5%.

In this study, wheat straw particle boards were produced by using a mixture of polypropylene with urea formaldehyde resin and its properties were investigation. The ratio of polypropylene to the wheat straw particles was as 10:90, 20:80 and 30:70 percent, respectively. Urea formaldehyde was used at three levels of 4, 6 and 8 percent based on oven dried weight of wheat straw particle. Mechanical and physical properties (modulus of rupture, modulus of elasticity, internal bonding, water absorption and thickness swelling after 2 and 24h soaking in water) of the produced boards were measured. The results showed that increasing polypropylene with urea formaldehyde resin to wheat straw particles, resulted in increasing the bending strength, modulus of rupture and modulus of elasticity of the boards. The results also indicated that water absorption and thickness swelling after 2 and 24h soaking in water decreased with increased polypropylene with urea formaldehyde resin percent. The UF resin content can be reduced in the particleboard as a function of increasing the PP powder.

This study was conducted to investigate the effect of Cu nano Particles on density profile and mechanical properties of medium density fiberboard. One layer fiberboard (MDF) with a density of 0.58g/Cm3and a thickness of 17 mm were produced using Cu nano particles in three levels (5, 10 and 15wt%based on solid content of resin) and Urea formaldehyde resin content in two levels (8 and 10wt%based on oven dried fibers) as Variable factors. The control panels produced using 10 % resin without cu nano particles (based on oven dried fibers) with the same characteristics of other panels. Mechanical strength including internal Bonding (lB), Bending strength, Modulus of elasticity and density profile using slicing method were determined. The results indicate that increasing the amount of Cu nano-particles had no significant effect on the internal Bonding as well as bending strength and Modulus of elasticity of panels.The increasing of resin content from 8 to 10percent improved 43.7% modulus of elasticity.18.9% bending strength and 23%internal bond of panels. In addition the increasing of Cu nano particles up to 5% caused relatively higher IB for panels produced using 8%resin in compare to the control panels(containing10% resin) as well as their density profile are more uniform and have the lowest differences between maximum and minimum density in the density profile

In this study the GMDH neural network based on genetic algorithm to predict the physical and mechanical properties of particleboard laboratory scale has been used. predict the mechanical and physical properties of particleboard we used input parameters such as neural network including time of press closing (10،20 and 30) s، moisture mat (8،10،12 and 14) % and temperature press (150،160،170 and 180) °C as the input data and the output data is used as the physical and mechanical properties. The efficiency of these techniques evaluated with statistical criteria of mean square error (MSE)، root mean square error، (RMSE)، mean absolute deviation (MAD) and the correlation coefficient (R2). Results showed that the values of MSE، RMSE and MAD for properties MOR، IB، TS24h، TS2h، WA2h and WA24h is low. Errors were obtained for the MOE model was very high. According to the values obtained from MOE is not the appropriate model to predict. R2 values obtained from the test and training set properties for MOR، IB، MOE، TS24h، TS2h، WA2h and WA24h more than 0. 91%، Which reflects the performance of these models is better.

In this research the effects of acetylation in prevention of white-rot and brown-rot fungi deterioration on medium density fiberboard (MDF) were investigated. Sample boards were made from acetylated poplar fibers, which were treated in different time (0, 30, 90 and 270 minutes) to obtain different weight percent gains (WPGs of 0, 4.85, 9.1, and 15.8 %). There were twelve sample boards with considering of three replication for every treatment. The results were analyzed based on a complete randomized design (CRD) under a factorial experiment.Results revealed that the acetylation decrease deterioration effect of white-rot and brown-rot fungi. As it was determined, the weight descending of acetylated boards with the highest WPG (15.8 %) after 16 weeks were measured 1.605 % and 16.93 % for white and brown-rot fungi, respectively; while it was determined as 39.96 and 49.31 percent in untreated boards. The research results showed that the acetylation enhances biologic resistance in the medium density fiberboard.

The effect of the application of different contents of canola particles in the production of particleboard on its acoustic properties were determined using free vibration on free-free bars procedure. 33 samples from each combination of canola and wood particles were prepared and the acoustical properties were determined. Results showed that as the content of canola particles in the combination of particles increases, the modulus of elasticity and acoustic coefficient of boards increased from 1260 MPa and 121.16 m4/s.kg to 1560 MPa and 128.70 m4/s.kg respectively. At the lower content of canola particles in the particles mixture, because of unhomogenity, damping factor increased but by increasing the content of canola particles more homogeneous boards were obtained and damping factor decreased. Also, results showed the significant increase in acoustic coefficient efficiency by increasing the content of canola particles. Therefore as the results revealed, incorporating more canola particles in the particleboard mixture, acoustic properties of particleboard improves and the product can be used in acoustic environments, halls and etc.

This research was accomplished to investigate the bleaching of combined old newspapers (ONP) and old magazines (OMG) deinked by sodium dithionite. The bleaching of pulp was performed using a 0.5, 0.75, and 1% sodium dithionite and different times of 30, 60 and 90 min. The pulps were refined up to freeness of 300 ml, CSF and standard handsheets made from them. The optical and mechanical properties of paper and COD of bleaching effluent were measured according to TAPPI standard methods.The results showed that the brightness of paper was increased significantly with increase in the time and sodium dithionite charge. When the charge of bleaching agent increased, the mechanical properties of paper and COD pollution load of bleaching effluent were increased and paper bulk and opacity decreased but these changes were not statistically significant. Increasing in bleaching time from 30 to 90 min resulted in a significant improvement in tensile, burst and tear indices and decrease the opacity of paper.

In this study the effect of boiling water pretreatment on yield and optical, physical and mechanical properties of NSSC (Neutral Sulfite Semi Chemical) pulp of Golestan province wheat straw was investigated. Splinted wheat straw was pretreated with the boiling water (100 degrees) in the 10:1 ratio for 30 minutes. NSSC pulping carried out at constant condition including liquor to straw 10:1, maximum temperature 160ºC for 30 minutes. In order to study the effect of NaOH on strength properties of paper in some cases only Na2S03 were used. After pulping defibration was done by laboratory refiner to achieve 380±25ml (CSF). Hand sheets from each pulp with 60 gr/m² were made. The strength properties determined on the basis of TAPPI standard. Results show that pretreatment have a desirable effect on increasing the strength properties of papers such as and tensile, burst, breaking length, stiffness and density, except RCT strength other strengths of paper increase. Measuring the freeness of pulps showed that by increasing chemical contents specially NaOH freeness, yield, thichness and bulk decreased and density increased.

In this study sound absorption coefficient and hardness of gypsum particleboard produced with kenaf stalk and nano clay were investigated. Variables in this study were weight ratio of kenaf stalks to poplar wood in three levels (40, 50 and 60 %) and nano clay content (0, 3 and 6%) based on dried mass of wooden particles. Sound absorption coefficient determined according to ISO 10534-1 and hardness was measured in accordance with the ASTM D-1037 standards. The sound absorption coefficient was measured at four frequencies of 250, 500, 1000, and 2000 Hz. The obtained results showed that with increasing frequencies, sound absorption coefficient increased. With increasing ratio of kenaf stalk in boards, hardness decreased, but sound absorption increased. Furthermore, increase in percentage of nano clay used in the boards increased the hardness and reduced the sound absorption in coefficient in gypsum particleboard. Generally, the highest sound absorption coefficient was shown the boards produced with 60% kenaf and without nano clay in frequencies of 2000 Hz.

In this study, physical properties of composite with manufacturing recycling polymers (polypropylene and polyethylene) filled two types paper mill sludge (sludge on the DAF and water waste sludge) were investigated. There levels of paper sludge (15, 30 and 45 wt %) were used to produce composites. Haake machines were used to blend materials and in order to produce standard samples; injection molding system was utilized. Density, water absorption and thicknesses swelling as physical properties composites were investigated. The increasing of both paper mill sludge (sludge on the DAF and water waste sludge) to the recycling polyethylene and polypropylene cause to increased of density composites. But, compare of date obtained from density measuring with other researchers showed that utilization paper mill sludge cause to relatively low composite density and low cost on the unit volume basis. With adding both paper mill sludge (sludge on the DAF and water waste sludge) water absorption and thicknesses swelling increased. The samples including polypropylene and water waste sludge lower water absorption and thicknesses swelling compared with other composite showed.

The work is related to the effect of old corrugated container (OCC) as Urea Formaldehyde resin (UF) extender on properties of medium density fiberboard (MDF) prepared from Bagasse and MDF waste as a partial substitute of fibers. The important variables in this research were ratio of UF resin powder to OCC (at five levels; 100:0, 5/5:1/98, 97:3, 5/5:4/95, and 94:6) and ratio of bagasse fibers to MDF waste (at five level; 100:0, 98:2, 96:4, 94:6 and 92:8). The fixed factors in all treatments were 6 mm/min for press closing time and 150° C for press temperature. Thickness swelling (TS), water absorption (WA) after 24h, modulus of elasticity (MOR), modulus of rupture (MOE) and internal bonding (IB)) of panels were investigated according to EN standard and statistical analysis was performed using SPSS software. The results clearly showed that waste paper powder and MDF waste had a significant effect on the bending strength and modulus of elasticity. Significantly, an increase in OCC can improve internal bonding (IB) while it can be reduced by increasing of MDF waste. Minimum water absorption was found in panels with maximum MDF waste content. It means the panels with 8 percent MDF waste had the least absorption. Moreover, the panels with highest content of MDF waste had the least thickness swelling. No significant difference was found between the effects of various OCC content on the physical properties while it had a meager increase on water absorption and thickness swelling.

Bio and synthetic polymers; micro and recently nano particles were developed in wet end section of papermaking industry. Very special attention is toward their advantages for controlling the process variables and improving of product quality made from recycled papers. In the presence of cationic starch polymer as an anionic trash reducer of pulp, the effects of cationic poly acrylamide (CPAM)-bentonite nanoparticle complex were evaluated on retention, drainage and paper properties made from old corrugated container (OCC). The results showed that addition of CPAM polymer individually enhanced burst, tensile and tear strength indices. The use of nano bentonite following CPAM has significantly increased all of mentioned pulp and paper properties. Dewatering rate analysis by Dynamic Drainage Jar and laboratory hand sheet maker revealed time reduction for the paper manufacturing. Moreover, raw material to final product ratio (total retention) increased from 96.7% up to 98.7%. Long chain cationic poly acrylamide has high capability in the flocculation of papermaking ingredients, individually and particularly in combination with nano bentonite, especially for fiber fines which have a high portion in recycled pulps; thus the problems resulting from unretaining of the ingredients and then their entrance to the process water and finally the paper mill waste water, will reduce.

This study was conducted with the aim of fabricating lab-scale samples of transparent papers with overbeating method. Hence, bleached soda pulp from bagasse fibers was subjected to post-bleaching with sequence of DED to remove any residual chromophores. Then this pulp was refined with PFI mill to achieve different levels of 55, 130, 200, and 260 mL,CSF (Canadian standard freeness). Results indicated that refining has significant effect on optical properties especially transparency so that the maximum value was observed in handsheets made of pulp according to TAPPI standard T 205 om - 8 with least freeness, i.e 55 mL. The variations of transparency due to refining were also further explained by measuring scattering coefficient, opacity and brightness of the specimens. In addition, mercury porosimetry and analyzing the pictures of scanning electron microscopy (SEM) demonstrated the severe variations of pore structure in paper during refining which have great influence on developing transparency.

Microbiological degradation of wood and wood products is one of the most important of their disadvantage which Reduce its useful life. There are various methods to increase the natural durability of wood and wood products that in the most of them by using chemical reagents. In the past years the thermal modification as a ecofriendly method has been used in many times. In this research the effects of steam pretreatment on the fungal durability of particleboard were studied. Steam pre-treatment was applied on the particles of poplar wood in a stainless steel reactor at four temperature levels (155, 165, 175 and 185 ºc) and three retention time levels (15, 30 and 45 min). The amounts of Hemi cellulose. Acetone extractives of wood particles as well as EMC and Mass loss of test panels were measured.The results indicated that the steam pretreatment caused to decrease significantly the amount of Hemi cellulose of wood particles, EMC and mass loss of test samples where as the amount of extractives of wood particles increased.According to the results, the variation of Mass loss of particleboard test samples showed a significant correlation to the variation of EMC of test samples,Hemicellulose and extractives amount of wood particles when the wood particles thermally pre-treated at 165ºC for 30 minutes