Iranian Journal of Wood and Paper Science Research
Year:2019 | Volume:34 | Issue:1 (66)|Papers Count:13

Simultaneously providing different but paradox properties of paper products has been the utmost challenging issues of papermakers, e. g., reaching proper strength combined with high water absorbency in hygienic papers has been an issue. For example, higher fiber bonding results in lower accessibility to the hydrophilic functional group. Therefore, hydrogel has attained increasing importance in bulky cellulosic diapers. In this study, surface coating on paper was investigated and compared with distillated water saturated papers. The chitosan-acrylic acid (AA) hydrogel was converted to nanoparticles using ultrasonic homogenizer and Dynamic Light scattering (DLS) confirmed the dimension of Nano scaled particles. SEM images and paper caliper revealed the formation of Nano-hydrogel coating layer on paper. The water uptake of all papers coated with 1, 1. 5 and 2% Nano-hydrogel increased significantly up to 50% compared to the untreated sample. Burst and dry tensile strengths were improved in a similar way as with water uptake, but tear strength was unchanged. Increased fiber bonding due to the presence of carboxylic acid in AA combined with hydroxyl and amine groups in chitosan, and the reinforcing effect of Nano hydrogel film formation on the cellulosic substrate resulted in strength improvement. Wet tensile strength of paper revealed remarkable increase at 2% coating application, but providing negligible enhancing effects at the lower dosages. Paper opacity, brightness and whiteness remained almost unchanged, but due to chitosan yellowish nature, the paper yellowness increased. The coated paper stiffness enhanced compared to untreated paper, but revealed lower stiffness than water saturated papers. The caliper, tensile and burst indices of water treated papers were reduced and stiffness increased.

One of the most important sources of environmental pollution is dye from industrial wastewater which is harmful for human health and environment. Therefore, the aim of this study was to evaluate the removal potential of Methylene Blue (MB) dye from aqueous solutions by saw dust modified using ultrasonic wave with response surface methodology. The batch experiment was conducted to evaluate the effect of dye concentration, contact time, adsorbent dosage and pH on dye removal from aqueous solution. Response surface methodology was applied to appraise the effect of these different variables. The dye concentration in the solutions was measured by spectrophotometer at the wavelength of 664 nm. The results showed that the optimum parameter values for maximum color removal efficiency were: dye concentration 20 mg/L, reaction time 8 min, dose of adsorbent 4 g/L and pH=9. The Maximum and minimum dye removal were obtained at 92. 29 and 47. 5 percent, respectively. Analysis of variances test showed that the quadratic model was the best model to explain the interaction of variables. Based on analysis of variance (ANOVA), the coefficient of correlation value (R 2 =0. 9116) was high, showing that the experimental values fitted well with the predicted values. In addition, the statistical analysis of the results indicated that in the range studied, dose of adsorbent and pH had a significant effect on color removal efficiency. The Gibbs free energy and enthalpy data verified its spontaneous and endothermic nature. In addition, survey of pseudo first and second order kinetics models presented that the adsorption process was compatible to pseudo-second order kinetics equation.

In this research, the effect of coating with Polycaprolactone (PCL), nanocrystalline Cellulose (NCC) and zinc oxide Nanoparticle (ZnO NP) and their blend on the mechanical and optical properties of handsheet papers were investigated. First, coating materials with specific condition (PCL 10%, NCC 4 and 6%, ZnO 3%) were coated on the papers. The coating materials weight on the papers was (2. 2-2. 7 g/m 2 ). The results showed that the mechanical properties (Tensile strength index, Burst strength index and Tear strength index) of the coated papers were enhanced with addition of NCC. The ternary blend of these coating materials had the highest mechanical properties than the untreated papers. With addition of NCC, the brightness was enhanced and the opacity was reduced. Also, the color indices were improved with addition of NCC and ZnO and the effect of ZnO was more remarkable than NCC, but in ternary blend of materials, the color indices were improved with increasing the amount of NCC.

Mold growth resistance of Polyurethane and Diotrol coatings containing natural (Thyme essential oil) and synthetic (IPBC) fungicides in both ordinary and microencapsulated forms was studied. Polymethyl methacrylate (PMMA) microcapsules were prepared using solvent evaporation method by means of oil emulsion formation in water. Mold growth resistance against Aspergillus niger was determined using Filter Paper Disc method before and after aging process as defined in ASTM D 5590 Standard. Adhesion strength and surface roughness of coated samples were also measured. Results revealed that biocide-free coatings cannot provide adequate protection against mold growth, and addition of biocides, especially IPBC, significantly improved the mold growth resistance. Even after the aging process, microencapsulated biocides were able to provide better protection against mold growth due to controlled-release mechanism and shielding-effect of polymeric shell. Although the surface roughness of polyurethane coating was increased by using of biocides in both forms, especially microencapsulated ones, its adhesion strength reduced.

In the present research, the biodegradability of poly-lactic acid-canola stem flour composites in three levels of 25, 35, and 45% canola stem flour made by compression molding technique were studied. In order to study the biocompatibility behavior of the composite, three methods of biological degradation were used for Trametes versicolor and Gloeophyllum trabeum fungi, longterm water absorption and soil burial for 4 months. The results of statistical analyzes showed that the composites weight loss due to the degradation by fungi and burial in the soil was imcreased as the amount of rapeseed canola stem flour in the composite increased while pure poly-lactic acid showed a very high durability against these agents. In addition, there was no effect on the weight loss of samples in the long run leach test so that the weight of composites and poly-lactic acid samples was constantly increasing and there was no effect on weight and thickness loss. The growth of fungi myceliums was clearly detectable and also detectable in images of electron microscopy from the fracture properties of composites. Unlike poly-lactic acid, fungi myceliums crossed the polymer into rapeseed stem flour and reduced the weight of the composites. The results of the FTIR spectroscopy on poly-lactic acid before and after exposure to the Gloeophyllum trabeum fungus confirmed the validity of the above results. According to the results of this study, poly-lactic acid, as a biodegradable polymer, has been shown to be very durable against degradation by natural biological agents.

In this study, the effect of bagasse piling storage method on the physical and mechanical properties of particleboard was studied. Wet depithed bagasse was used. Bagasse storage conditions included two moisture content (45% and 55%) and 4 storage times (1. 5, 3, 4. 5, 6 months). First, bagasse chemical characteristics (pH, acid and alkaline buffering capacity) were determined. Then particleboards were fabricated. The physical and mechanical properties of the boards were measured and statistically analyzed. The results showed that at lower Bagasse moisture content, the sample pH and alkaline buffering capacity were decreased and acid buffering capacity increased. Also board bending properties (modulus of rupture and modulus of elasticity) and thickness swelling after 2 and 24 hour immersion in the water were reduced. Bagasse chemical properties tend to be acidic up to storage time of 3 months and the minimum of board bending properties and internal bond were reached in this storage time. The physical properties of boards were improved with increasing of storage time.

A need for control of pathogenic microorganisms in contaminated environments has motivated to prepare the products such as antibacterial papers which resists growth of such organisums. Different methods and materials have been used to make these papers. The purpose of current research is to fabricate silver nanoparticle by means of plasma method and investigate the effect of adding such nanoparticles on the properties of resulting kraft papers Silver nanoparticles have been produced in optimized conditions of 1 kHz frequency, 2 A current and 4 kV voltage, using an instrument developed in Laser and Plasma Research Institute, Shahid Beheshti University. The DLS test confirmed the average size of silver particles at nano scale ( 41. 2 nm). Then, the prepared silver nanoparticles were added at the levels of 0, 25, 50 and 75 ppm to the kraft pulp using cationic polyacrylamide (CPAM) at the dosage of about 0. 05 based on oven dry of fibers as retention agent. The results of paper properties evaluation (having basis weight 60± 3 g/m 2 ) have shown that addition of silver nanoparticles synthesized by plasma method lead to loss of paper strength. The paper brightness has also exhibited a meaningful decrease. However, the paper opacity and antibacterial property was significantly developed at the consumption levels of higher than 50 ppm.

This study deals with the possibility of evaluation and estimation of the wood density of Oak (Quercus castaneifolia) and Beech (Fagus orientalis) wood. First, wood samples were prepared and cut in 4×20×30 cm (thickness×width×length). Then their density was calculated after 72 hours conditioning in an oven at 60° C temperature. In thermography process, the temporal temperature was monitored in 1 st th, 5, 10, 20, 30, 45 and 60 th minutes of cooling (monitoring steps). For investigating the effects of shape factor and dimension on thermographic density evaluation errors, the specimens were cut down two more steps to 3×20×30 cm and 2×15×20 cm and the course of thermography experiments was repeated. The relationships of shape factor, density and the ratio of density to the shape factor with the logarithmic cooling rate were evaluated separately. Results showed that density without considering the shape factor variations was not sufficiently correlated to the cooling rate. However, the ratios of the density to their proper shape factors were promising for the density evaluations from the cooling rates. Finally, it is suggested to revise this non-destructive method using a larger variety of the wood specimens and species.

In this study, EVOH was coated on paper made of CMP pulp by extrusion method to improve the paper barrier properties against oxygen transmission. Ethylene vinyl alcohol (EVOH) shows poor moisture resistance despite low gas permeability. Therefore, dimethoxydimethylsilane was deposited on EVOH coated paper using Plasma Enhanced Chemical Vapor Deposition on EVOH film as the hydrophobic layer. A random factorial experiment was designed with three factors at three levels including time (6-8-10 min), pressure (30-0400-500 m Torr), and radio frequency power (50-70-90 W). The contact angle, oxygen transmission rate, tensile strength, and strain energy were measured to obtain the optimum condition. Expert Design method using response surface was used to optimize the condition coating of dimethoxydimethylsilane in order to improve the hydrophobic properties, reduce OTR, increase tensile strength and strain energy. RSM method for optimum condition was suggested as: time 6 min, pressure 499. 99 m Torr and power 50W.

Nowadays, the barrier property against water uptake of different packaging papers which are mostly prepared using recycled fibers is of highl important for paper manufacturers. In current study, the effect of AKD sizing agent has been examined on the properties of papers made from recycled fibers of Atrak pulp and paper industries. Sizing of pulp suspension using AKD was conducted at levels of 0, 0. 5, 1 and 1. 5% based on oven dry (OD) of pulp in neutral pH ( 7), according to the TAPPI standard methods. Then, handsheets with basis weight of about 60± 3 g/m 2 were prepared and the Cobb test (60 second) and different characteristics were evaluated. According to the statistical analysis of the results, up to 1 % AKD consumption added based on OD pulp exhibited optimum level in internal sizing of these recycled fibers. In such AKD level, water uptake of size-free papers which was measured at 174± 7. 4 g/m 2, was decreased to the value of about 24± 1. 7 g/m 2 in AKD-treated papers. Furthermore, contact angle of water droplet on the paper surface increased from 35. 2º to 109. 1º . Applying 1 % of AKD, paper tensile index increased to 33. 2± 1. 01 N. m/g by 2. 4 unit compared to the base paper. Apparently, such phenomena can be attributed to the AKD potential in creating hydrogen bonds which concurrent to the development of paper water repellency, resulted in improving bonding-ability of paper network. Additionally, AKD treatment led to meaningful increase of paper opacity. This can also be attributed to the increased filler retention in the fibers network, which influences the development of light scattering from the paper surface.

Rice straw is among the important lignocellulose residues in Iran and the world. In this research, rice straw as renewable lignocellulosic materials were used to produce Nano-structural lignocellulosic aerogel. For this purpose, rice straw powder was first pre-treated in sodium hydroxide aqueous solution and the resulting gel mixture was transformed into physically bonded lignocellulosic porous and ultra-lightweight aerogel through consecutive processes including freezing-thawing, solvent exchange and freeze-drying. The product properties including apparent density and total porosity were determined, and other physical and chemical properties were evaluated using SEM, FTIR, XRD, nitrogen absorption (BET) and DSC methods. The results showed that a significant portion of the rice straw compounds were dissolved in aqueous alkali solution and removed during the subsequent stages of aerogel production. The resulting aerogel showed a nano dimensional structure composed of particles and interconnected nanofibers, which had a great chemical and physical difference from the original rice straw.

Wood is a natural material, and human beings for a long time have been in close contact with wood. Psychologically, wooden structures, and any kind of wood-craftsmanship give people a sense of relaxation. This research was conducted to investigate the relationship between wood color and wood decors at work and living on emotional and psychological reactions of individuals. In this investigation, 384 individuals from Karaj city were selected as random sampling method. In this research, a researcher-made questionnaire was used. In inferential statistics, SPSS tests including Kolmogorov-Smirnov test (for data normalization) and correlation test were used. Results of statistical analyzes revealed that, research hypotheses based on the effect of the color of the decor of the place of residence and work on the psychological reactions and emotional affirmation was confirmed.

In this study, the possibility of three-layered oriented strand board production from hornbeam (Carpinus betulus L. ) wood was investigated. Two press times (6 and 8 minutes) and three press temperatures (180˚ C, 200˚ C and 220˚ C) were applied and 12 mm thick laboratory boards were made from hornbeam wood strands. The strands on the surface layers were aligned in the longitudinal direction of the board and the middle layer strands are cross aligned to the surface layers. In all treatments, board density of 0/7 g/cm 3 and mat moisture content of 7% and phenol-formaldehyde resin (PF) content of 7% based on the oven dry weight of the strands were kept constant. The mechanical and physical properties of the boards were measured as defined in relevant European standards test methods EN 300. The internal bond (IB) and thickness swelling (TS24) of boards were significantly improved as the press time increased from 6 to 8 minutes. The modulus of rupture (MOR) and internal bound (IB) and thickness swelling (TS24) were significantly improved as the press temperature increased from 180˚ C to 220˚ C. Overall results showed that the highest MOR and IB and the lowest TS24 were reached at 8 minutes press time and 220˚ C press temperature and the properties of all boards made applying these conditions exceed the EN 300 standards values for MOR, MOE, IB and TS24.