مجله تحقیقات علوم چوب و کاغذ ایران
سال سی و پنجم شماره 2 (پیاپی 71، تابستان 1399)

This study uses the Lignin-Glyoxal adhesive to replace chemical resins with environmental compounds producing plywood. producing plywood, pure Lignin (L.100%), lignin- glyoxal 15% (L.85-G.15), lignin-glyoxal 30% (L.70-G.30) and Urea-formaldehyde (control) were used as adhesive at 160 gr/m2 level. Accompanied with ammonium chloride (1%) as the hardener and wheat flour (30%) as the filler based on the dry weight of the adhesive characteristics of adhesives included solid material percentage, viscosity, specific weight and PH were measured. After producing the laboratory boards, the physical and mechanical properties of samples, such as thickness swelling after 2 and 24 hours of being soaked in water, shear strength, modulus of rupture, and modulus of elasticity were measured. In addition, the groups and bonds in the pure lignin and lignin-gloxal adhesives were identified by Fourier Transform Infrared (FTIR) spectroscopy. The results indicated that the independent effect of adhesive type on the thickness swelling of plywood after 2 and 24 hours was significant. Although the results suggest that modifying the lignin would improve the plywood in all cases, the control boards had better featurers than those made with the Lignin-Glyoxal adhesive.

In this study, the effect of nano-wollastonite on physical, mechanical and morphological properties of composites made of bagasse and gypsum was investigated. The mixing ratio of sugarcane to gypsum pulp at three levels (80:20, 70: 30 and 40: 60%) and nano-wollastonite at three levels of zero, 3 and 7% were considered as the variables of this study. The thickness of the test boards was 16 mm cake density of all boards was considered to be 1.10 gr/cm3. Then the mechanical and physical properties of the specimens including modulus of rupture, modulus of elasticity, internal bonding, water absorption after 2 and 24 hours immersion and density of boards according to DIN-EN-634 and fire resistance (weight loss percentage) according to ISO 11925 Were measured. In this study, a thermocouple and a flask were used to measure the hydration heat. Microscopic images (SEM) were obtained from the fracture surface of the specimens to investigate the common boundary between bagasse-gypsum and nano-dispersion. The results showed that with increasing bagasse mixing, the modulus of rupture, modulus of elasticity and internal bonding decreased and water absorption and weight loss percentage of boards exposed to fire increased. Application of nano-wollastonite up to 7% improved all mechanical and physical properties of composites. Also, microscopic imaging (SEM) showed that the optimum level of nano-wollastonite can fill vacant voids due to gypsum hydration and create a uniform structure.

Clearing of paperwork and documents is one of the main steps in protecting and restoring these works. Considering the fact that the stains generated by hand contact due to numerous page turning of books on the surface of the paper, the appearance and aesthetics of the book pages are distorted. It also chemically degrades cellulose tissue; therefore, removing it is important in the process of protecting paper documents. Different methods and chemicals are used to remove various stains on paper, including organic solvents which are flammable and toxic, therefore, the use of some methods and materials for paperwork, as well as the health of restorers and even the environment, are hazardous. This research evaluates the Enzruth gum extract at different concentrations for removing stains generated due to hand contact, based on the advice of ancient texts, in order to resolve such problems. Maceration (soaking) method was used to extract gum. Fourier transform infrared spectroscopy was used to evaluate the sample with historical samples and colorimetric, pH-meter methods, macroscopic and microscopic observations with digital loop were used to evaluate the detergent rate of the extract. The results of observations and calculations of color variations and acidity indicate the cleansing power of the hydroalcoholic extract of Enzruth gum with an increase in its concentration with respect to the stain density thus, a more favorable and acceptable cleansing can be evaluated. This research is an applied and analytical-descriptive method that resulted in the finding of documents and experimental data, and finally conclusions were obtained by analyzing the information gathered

The purpose of this research is to evaluate the effect of various paper coatings on initial contact angle and its evolution over time. We investigated nine coatings on two types of 75 g and 125 g printing papers. Seven coating compositions containing 80% clay, 20% ground calcium carbonate, dispersing agent and various levels of polyvinyl acetate and lactic acid as binders were used. In the last two coatings, we used 100% precipitated calcium carbonate pigments, cationic starch, methacrylate, dispersant and two levels of cellulose nanofibers. In these suspensions, the amount of cellulose nanofibers in composition 8 is twice composition 9. After coating using rod method, the papers were dried then coated and control samples were calendered. We then performed contact angle measurements using water droplet and Kit No were performed. We noticed largest contact angle and smallest angle change over time for sample 6 containing 75% binder. Last two coatings contained cellulose nanofibers, which caused presence of hydroxyl group on the surface and lowered the contact angle. Composition eight was the most hydrophilic sample. Best barrier property Kit No and largest droplet volume after 20 seconds was accompanied with the increase of the binder percentage in the formulation. For the control sample and three treatments with highest binders, the contact angle over time remains relatively constant which is a sign of hydrophobicity. The correlation between contact angle and volume of the water droplet was determined to be 0.951 and 0.936 in the 75g and 125g papers relatively. We did not notice a significant difference in contact angle and Kit No between 75g and 125g samples.

The widespread use of chemically/thermally modified wood in outdoor applications and in environments with high relative humidity and high temperature has doubled the importance of using hydrophobic monomers. To evaluate the effect of fluorocarbon modification as a binder on the physical properties and chemical structure of paulownia wood, thermal modification was performed at two temperature levels of 150 and 160°C and chemical modification with fluorocarbon at two levels of 15 and 25%. Chemical/thermal modification causes the fluorocarbon monomer and heat to be uniformly transferred into the wood and to reduce its hydrophilicity by causing chemical changes in the wood structure. Specimens were divided into control, thermal and thermal fluorocarbon treatment groups. The thermal fluorocarbon treatment caused modification of the hydroxyl groups and hydrophobicity in specimens. Infrared spectroscopy confirmed the presence of fluorocarbons and bonding with wood polymers. The fluorocarbon reaction resulted in chemical changes, weight gain and bulking of the specimens. The water uptake and volumetric swelling of the heat-treated fluorocarbon specimens were lower than the control and heat-treated ones. Improvement of water repellency efficiency and anti-swelling efficiency of thermal fluorocarbon specimens increased the dimensional stability compared to the thermal control and created a super hydrophobic and leak-resistant coating on the cell walls and inside the lumens. It was attributed to the greater penetration of fluorocarbons and the reduction of wood porosity.

The effect of applying the sequence of enzymatic treatment and refining was investigated on the properties of deinked pulp from mixed office waste paper (MOW). Refining was applied for 700 and 1500 revolutions. Enzymatic treatment was applied for 60 minutes with temperature of 60°C and 13% of consistency. Applying enzymatic treatment led to decrease in strength properties of paper and also decrease in freeness of the pulp. The refining process resulted in increase of paper properties and decrease in freeness of the pulp. By applying enzymatic treatment before refining, the freeness of pulp changed significantly so that, the freeness of the pulp was 496 and 390 for 700 and 1500 refining revolution respectively just for refining but these numbers changed to 397 and 544 for same revolutions for “enzymatic treatment + refining” sequence. In a normal condition increase of refining revolution lead to decrease in pulp freeness but that was interestingly the freeness increased for 1500 refining revolution. This means that the enzymatic treatment was effective. Generally, refining itself improved the quality parameters of pulp and paper, but applying this process after enzymatic treatment changed everything.

The most important challenges of using minerals and fillers in the papermaking process are low retention and sharp reduced paper strength properties. In this research, magnetic papers were synthesized using commercial kraft fibers and iron salts. Nano-iron oxide has the same performance as fillers, as a result, to prevent reducing strengths properties and retention of material in the final paper, chitosan uses as a strength agent and retention aid at 0, 10 and 15% levels. Characteristics of magnetic papers were investigated by atomic force microscope, scanning electron microscope, X-ray diffraction and vibration sample magnetometer. Tensile index and tear index were also determined in magnetic paper samples. The results of the microscopic examination showed that the magnetite nanoparticles were in the size range of 1 to 84 nm and the magnetic materials completely covered the fibers surface. Also, increasing chitosan content, increased the degree of loading and magnetic saturation of the samples. The magnetic paper samples had super para magnetic behavior. The results showed that adding chitosan at 10% increased tear and tensile strength but 15% chitosan decreased the strengths properties of magnetic paper.