IRANIAN JOURNAL OF WOOD AND PAPER INDUSTRIES
Year:2018 | Volume:9 | Issue:3 |Papers Count:12

Rigid polyurethane foam (PUF) with desirable properties such as low thermal conductivity, easy production and processing is extensively used in the industrial applications. Currently, the PU industry is heavily petroleum-dependent, because its two major feedstocks, i. e. polyols and isocyanates, are largely petroleum-derived. Due to concerns over the depletion of fossil resources and pollution, there has been a great deal of interest in developing bio-based polyols from renewable resources. Lignocellulosic biomass is considered to be suitable for production of bio-based polyols, having hydroxyl group rich compounds. In bio-refining processes, the lignocellulosic macromolecular are broken down and converted into a viscous liquid using certain solvents. The use of high volumes of liquefaction solvents increases the production cost of bio-polyols. This has led to research on low cost and renewable solvents such as crude glycerol. In this research crude glycerol was used as a solvent for liquefaction of sawdust and polyol production. The influence of process variables such as reaction temperature and time on polyol properties, namely biomass conversion ratio, acid number, hydroxyl number and viscosity were measured according to the certain standards. With increasing liquefaction temperature, increased production efficiency and viscosity and acid, hydroxyl number of polyols decreased. Finally, polyol of liquefaction at 180 and 360 min with production efficiency of 51%, acid, hydroxyl number and viscosity of 9/7, 325 mgKOH/g and 18 Pa, s was determinate as optimum polyol.

The aim of this study was to determine stress carrying capacity of doweled corner joints in wood members made with modified resin (polyvinyl acetate) and comparing it with unmodified ones. Joint members were out of European silver fir (Abies alba) and dowels were made from beech and poplar woods as variables in this study. Diameter of dowel had three levels in size, namely 6, 8 and 10 mm. The experimental joints were tested under diagonal compression loads. Results showed that stress carrying capacity of tested joints made with modified glue is more than unmodified ones. Maximum stress capacity was observed in the joints of beech with 10 mm in diameter dowels. Based on the results, the highest strength belonged to those joints made with beech wood glued with modified resin containing 10 mm dowel. Furthermore, the lowest strength belonged to poplar joints made with unmodified resins and 6 mm dowels. The improvement can be due to an increased viscosity and controlled penetration of the resin into the wood structure and hence better bonding. Concerning the wood species, beech had the highest stress carrying capacity that can attributed to its higher density.

In this research, the use of alkali sulfite-anthraquinone liqueur (AS-AQ) powder as filler of urea formaldehyde resin (UF) and replacing it with wheat flour in the production of plywood was considered. The AS-AQ liquor powder was used as filler of UF resin in plywood manufacture at four levels of 0, 5, 10 and 15% based on oven dry weight of UF resin. Then, the physical and mechanical properties of the samples, including thickness swelling after 2 and 24 hours immersion in water, bending strength and modulus of elasticity (parallel and perpendicular to surface grain) and bonding shear strength were measured. The results showed that the amount of thickness swelling of the boards after 2 and 24 hours of immersion in water did not increase significantly, and all the levels had a thickness swelling at the standard level. Increasing the consumption of liqueur powder did not have a negative significant effect on the dimensional stability of the boards. Bending strength and modulus of elasticity parallel and perpendicular to the surface layer was improved by an increase in the use of liquor powder, but there was no significant difference between the levels. Therefore, considering the physical and mechanical properties of the boards, it is appropriate to use alkali sulfite-anthraquinone liqueur powder as filler of urea formaldehyde resin.

According to the importance of urea formaldehyde resin in plywood industry and to replace a suitable filler for this resin with wheat flour (common filler), lignin derived from three black liquors including alkaline sulfite-AQ, soda-AQ and Kraft was evaluated as filler-extender for urea formaldehyde resin in the plywood manufacture. For this reason any of the four types of lignins were used at 0, 10, 20 and 30% dry weight of resin. After that, the physical and mechanical properties of samples including thickness swelling after 2 and 24 hours immersion in water, flexural strength and modulus of elasticity parallel and perpendicular to the surface layer and shear strength were measured. The results of this study showed that increasing the lignin of alkali sulfiteanthraquinone and then kraft lignin, respectively increased the flexural strength and modulus of elasticity parallel to the surface layer. Also, the bonding shear strength of the samples using three types of lignins increased. On the other hand, the use of these three types of lignin, improved the dimensional stability of the boards. The results show the superiority of lignin from alkaline sulfite anthraquinone process compared to other lignins to improve the mechanical properties of plywood.

The use of cellulose nanofibers as strength-enhancing additive in the wet end section of paper machine increases the general strengths of paper. Nevertheless, considerable increase in draining time from pulp suspension and decrease in paper porosity and opacity has been reported as substantial restriction of its application in this section of papermaking. In this study, the effect of applying cellulose nanofibers in the forming section of paper was examined on the properties of three-ply paper made from recycled fibers. Samples of recycled fibers were prepared from Atrak pulp and paper industries. The refined and not dispersed pulps were, respectively, used to form top layer and other two layers. Standard sheets with 40± 2 g/m2 basis weight were prepared from each of the recycled pulps. Then, cellulose nanofibers were sprayed in 1, 2, 4 and 6 levels (based on oven dry weight of fibers) on one sheet surface and subsequently mild suction was done applying cellulose nanofibers spraying machine designed and fabricated in Zirab research campus. Finally, three-ply paper with 120± 5 g/m2 basis weight were prepared using treated sheets and its properties were evaluated. The overall results revealed that spraying cellulose nanofibers on the forming sheet led to an increase in tensile and burst indices of the paper about 33. 59 and 26. 29 percent, respectively. This process particularly had a considerable effect on the strength improvement between layers in multiply paper which is the most important in these kinds of papers. Thereby, the value of this strength has been significantly increased from roughly 116 J/m2 to 217 J/m2. SEM micrographs prepared from paper thickness confirm larger link between layers and multi-ply condensation.

The aim of this research were to facilitate the use of starch in paper works that combined they are not sensitive to water and also identify the characteristics of adhesives (sheets) enabled starch and starch together new. The research, analytical comparison and gathering data through experiments related to research like pH measurement, colorimetric, infrared spectroscopy with attenuated total reflection (FTIR-ATR), measurement of tensile strength and adhesion strength of the samples was also measured. The present study was thus that the adhesives were prepared rice starch and rice starch plate enabled. The prototyping was done using adhesives. Thermalhumidity accelerated aging specimens for 384 hours and changes color, pH, tensile strength and adhesion are studied. The results showed, the highest acidity after two rounds of the sample aging RS (tissue paper coated with glue rice starch) with pH 6/1 after the optical aging and 6/01 after Thermal-humidity aging as well as the lowest acidity of the average of the samples SF (plate starch) with pH 8/35 after optical aging and pH 8/20 after Thermal-humidity. after optical and Thermal-humidity aging, the highest tensile strength of the sample RS is the 1/08 kN per meter. Reviews results that the adhesion strength test showed after stage optical aging, the maximum adhesion of the is sample RS 1/32 Newton and after the Thermal-humidity aging of the highest adhesion into sample activated starch sheets (ASF) to amount 1/25 Newton.

The aim of the present study was to produce low density hybrid panels using expanded polystyrene granules (EPS) with different diameter and percentage. Expanded polystyrene granules used in 3 forms of fine, medium and large granules with an average diameters of 0. 55, 2 and 7 mm, respectively. The amount of EPS substituted in the core layer was 5, 10 and 15% based on oven dry mass of wood coarse particles. The results showed that the mechanical properties (modulus of elasticity, internal bond, face and edge screw withdrawal resistance) were significantly enhanced with increasing the EPS diameters. Increasing the amount of EPS from 5 to 15% also significantly improved the internal bond and physical properties. The bending properties and screw withdrawal resistance (both face and edge) were not significantly influenced with increasing the EPS content. The most important finding was that the improvement of all properties in core layer using polystyrene granules was higher in comparison with reference panels.

In this research, rice straw was used as a low-cost and abundant lignocellulose material for adsorption of acidic and reactive dyes from aqueous solution and their adsorption efficiency has been investigated. Rice straw was used after grinding and extraction. The studied dyes were Orangan 7 (AO7) and Rimozol Black B (RBB) obtained from Alvand Sabet Co. in Hamadan. In this study, the effect of pH, temperature, adsorbent and dyes concentration, and adsorption time were investigated to determine the optimum adsorption conditions. Also the adsorption isotherm was studied for both dyes. The results of color adsorption by rice straw showed that the amount of adsorption depended largely on the pH of the solution, and in acidic pH the removal of the dye by rice straw was high. Also, the dye adsorption at the initial stages of treatment is very fast and more than 95% of the adsorption of dye takes place at the first 10 minutes. The adsorption rate was studied using well-known adsorption models, and the results indicated that the equilibrium data for both dyes were perfectly described by the Langmuir isotherm. The maximum adsorptions of rice straw were 16. 5 mg/g and 27. 3 mg/g for RBB and AO7, respectively. Due to low cost and abundance of rice straw, it could be a suitable material for removal of dyes pollutants from industrial and municipal wastewater.

Wood and any items made from the wood may be destroyed by biologic and abiotic agents in unsuitable conditions. So far, different materials and methods have been developed to improve disadvantages of wood. Nowadays, researchers are looking for safe and eco-friendly preservatives due to the public concerns about the negative impacts of old ones. Borates are good candidate for new generation of wood preservatives due to the low acute toxicity for mammalians. Borates have board-spectrum efficacy, they are not only fungicide and insecticide but also act as a fire retardant. They are easily dissolved in water and can be diffused deeper into the wood over the time. This is also their biggest disadvantage. Preservatives based on the borate formulations may be easily leached out from the treated wood in the outdoor applications. Today, despite the problems coming from their leaching, they are widely used to protect wood and in particular wood-based composites due to their low toxicity. This study attempts to review the latest research on the possibility of using borates as pesticides and fire retardant in the industry of wood-based composites. Borates have a great potential for protecting wooden composites which are currently commercially used.

In order to use the design softwares for natural fibersthermoplastic composites in structural applications, precise determination of elastic parameters is of importance. Regarding the viscoelastic properties of these materials and their nonlinear stress-strain curves, even at low loading levels, determination of precise elastic parameters by common static tests is not simple. In the present study, methods of loadingunloading test was used to determine the elastic modulus of a natural fiber-thermoplastic composite and the results were compared with the tangent modulus obtained from static compression test. Dynamic modulus was also obtained from ultrasonic test, and a regression relationship was proposed between dynamic modulus and the static one. Results showed that the composite had orthotropic nature and the dynamic modulus from ultrasonic test showed higher values compared with the two others. Also, with increasing modulus resulted from unloading test, the difference between dynamic and unloading modulus decreased linearly. Results also showed that using prevalent method of modulus determination for this material (i. e. tangent modulus at 10-40% of ultimate stress) leads to the elastic modulus estimated much lower than the real value.

Acid prehydrolysis aiming to remove hemicelluloses is one of the key steps in producing dissolving pulp from wood resources. The objective of the present research was to resolve the necessity of using this treatment in dissolving pulp production from old corrugated container. Therefore, temperature of 130° C, acid concentration of 1%, time of 30 min and liquor to paper ratio of 7: 1 were selected as acid pretreatment and the properties of samples with and without prehydrolysis were compared after cooking. The results showed that except reactivity, other required properties of dissolving pulp including accessibility, degree of polymerization and the alpha cellulose content were diminished. Also, the results of yield and chemical composition indicated the destructive effect of this step on samples. Finally, regarding the superior properties of samples with no prehydrolysis and their acceptable value of reactivity, not only the acid prehydrolysis necessity was not acknowledged but also its application is not recommended.

Recently, using chitosan-nanosilica system in papermaking has been considered in several investigations. In the present research, confirming the performance of this nanoparticle system in producing paperboard from recycled old corrugated container pulp, the electrostatic performance of chitosan polyelectrolyte in process and product properties was investigated. In this respect, pH of pulp suspension, as one of the main factors affecting the chitosan electrostatic charge, was considered. The pH adjustment (5, 7 and 9) was done by hydrogen chloride and sodium hydroxide. The results indicated that the process properties (drainage and first pass retention) have been experienced better situation affected by chitosan electrostatic charge in neutral and alkaline conditions. It seems that by changing the pulp suspension pH to neutral and alkaline conditions, the chitosan positive electrostatic charge and its solubility decreases and in contrast, the fiber's negative charge increases. This condition probably affected the chitosan polymer attachment and adsorption status on fibers surface (loop and tail position) in a way that they performed more effectively in floc formation. Therefore, drainage and retention increased about 37. 5 and 36. 5%, respectively, compared with the control sample and 34 and 7%, respectively, in comparison with the acidic condition. Although the mentioned system was successful in increasing the mechanical strength compared with the control samples, but the electrostatic charge changes in different pH conditions had less positive impact on these properties (except internal bonding strength).