مجله صنایع چوب و کاغذ ایران
سال دوازدهم شماره 2 (تابستان 1400)

In furniture production, polishing processes are very important for the technical, economic, and aesthetic performance of wood materials. Thus, surface coating with paints can protect wood against specific environmental factors such as moisture, changes in dimensions, and degradation by microorganisms including fungi. This study aimed to investigate the effect of nano-wollastonite (0, 5, and 10%) on moisture resistance in sealer-killer and sealer-semi-polyester paints on Fagus orientalis, Abies sp, and Populus sp. The results showed that among the studied species, beech treated with nano and without nano had better adhesion resistance compared with Abies. Also, the performance of semi-polyester paint was better on tensile strength compared with killer paint. Finally, the highest adhesion resistance was related to the 5% nano-wollastonite.

In the current research, the feasibility of producing cellulose nanofibers from waste printing and writing paper and its potential for application as an additive in recycled pulp was considered. Although the origin of pulps for producing nanofibers were recycled ones, but they were hardly converted into nanofibers by mechanical force after mild acid pretreatment by applying 8% wt. of pure sulfuric acid relative to amounts of dry fibers in the pulp suspension with 1% consistency at 70°C for 1 hour. Analysis of nanofibers by transmission electron microscopy showed the successful production of fibers with nano-diameter (25-50 nanometer). Then, the ability of this product to improve the strength properties of recycled paper and also its effect on drainage of pulp (as one of the most important process properties) were investigated. In this regard, these cellulose nanofibers were added to the recycled fibers at 0, 3, 6 and 9% consumption levels (based on dry weight of pulp) with 1500 rpm agitation for 10 minutes. Results showed that all dosages of cellulose nanofibers had a positive effect on strength properties. The highest dosage of nanofibers improved the tensile and tear indices 31% and 17%, respectively. Also, nanofibers application didn’t change the opacity and brightness of the produced sheets. In addition, pulp drainage was decreased significantly by applying nanofibers. The results of current study showed the potential of nanofibers produced from recycled fibers for improving the properties of final papers, especially the mechanical ones and more aspects can be considered deeply in future investigations.

The conservation and preservation of historical paper as cultural and historical heritage against harmful factors such as microorganisms is important. It was shown that the thiophanate methyl antifungal in 200 PPM concentration could inhibit destructive effect of several fungi on paper without negative effects. However, it is necessary to complete the studies by investigation the effect of thiophanate methyl on other materials used in historical paper, including inks.In this research, the effect of thiophanate methyl on gall ink as the most widely used ink in historical paper was studied.For this purpose, after the ink preparation and placing it on the paper surface, the samples were immersed in a solution containing thiophanate methyl, and the effect of accelerated aging on gall ink and treated gall ink were investigated by determination of pH, color, and tensile strength of paper as well as by FTIR-ATR spectroscopy and SEM microscopy. The pH results showed that the gall ink is highly acidic, which causes the acid hydrolysis reaction lowering the paper strength. Moreover, thiophanate methyl in concentration of 200 ppm brightens the color of the gall ink. Due to the adverse effect of paper immersion on paper strength, the treatment should be conducted by spray method. Overall, although thiophanate methyl could protect the historical papers against fungus, but it showed various adverse effects on the gall ink that should be considered.

Enzymatic treatments have different effects on different types of pulps. In this study, the effect of cellulase treatment on drainage and dewatering capability and also paper strength properties of four types of first-hand (virgin) and recycled pulp was investigated. First-hand pulp included chemi-mechanical pulp (CMP) made from hardwoods (mixture of beech, hornbeam and poplar) of Iran northern forest and imported softwood bleached Kraft pulp (BKP) while recycled pulp comprised of old corrugated containerboard (OCC) pulp and deinked pulp (DIP). Both types of recycled pulps have been sourced from domestic factories in Iran. For enzyme treatment of pulp, the consistency of the pulp was set at 10%, the cellulase enzyme intake was 0.5% based on the dry weight of the pulp, the temperature, time and pH of the reaction were set at 50 Celsius centigrade, 60 min, and 5.5 to 6.5, respectively. From all kind of the pulp, before enzymatic treatment, fiber classification was performed in Bauer McNett fiber classifier and dimensional distribution of fibers and fine content in different types of pulp was determined. The results of this study showed that the effect of cellulase enzyme on chemical pulps with less lignin is more than semi-chemical pulp with more lignin and low cellulose. Cellulase enzymatic treatment increases the strength properties of pulp with more cellulose and improves the drain ability of the pulps with more fine content such as CMP and OCC.

The aim of this study was to investigate the mechanical, dynamic-mechanical and morphological properties of poly-capro-lactone/poly-lactic acid/cellulose nano crystal three-component nanocomposites. For this purpose, the nanocomposites were manufactured using casting solution method. Then, mechanical tests including tensile strength, tensile modulus and elongation at break and dynamic-mechanical test including storage modulus, loss modulus and loss factor were performed on nanocomposites. Field emission scanning electron microscopy was used to study the morphology of the nanocomposites and infrared spectroscopy was used to investigate possible reactions. The result showed that with increasing cellulose nano crystal and poly-lactic acid, the mechanical and dynamic-mechanical properties were improved. Field emission scanning electron microscopy confirmed the presence of nanoparticles in the nanocomposites and the results of infrared spectroscopy confirmed the hydrogen reaction between the hydroxyl groups of cellulose nano crystal with the carbonyl groups of poly-capro-lactone and poly-lactic acid, as well as the hydroxyl groups and carbonyl groups of both polymers with each other.

Black liquors are produced as a byproduct of chemical pulping and About 500 million tons of black liquor are produced annually in pulp mills around the world, of which about 95% for fuel consumption and only 2% for the production of special products with higher added value are used. In order to recover more effectively, acidic precipitation of black liquor using gas injection pretreatment has been studied recently. Previous studies have shown the advantage of carbon dioxide injection as pretreatment to reduce sulfuric acid consumption, increase yield and purity of lignin. The Iranian’s pulp and paper mills have the potential to recover lignin, which is burned as fuel. Therefore, this study was performed to investigate new methods of lignin recovery on hardwood Kraft black liquor in Iran. Pretreatment was done using carbon dioxide injection in lignoboost method as well as two-stage oxygen-carbon dioxide injection in Lignoforce method under 2 bar pressure and 80 ° C on Kraft black liquor, Then, the pH was decreased to 2-3 using 6 M sulfuric acid to precipitate the lignin, which was then separated by filtration and washed with water. Finally, the recovered lignin was dried at 50º C. TGA, FTIR, SEM and AFM tests were performed to evaluate the thermal stability, chemical structure, morphology and dimensions of recovered lignin. Also, acid consumption, yield and ash content were calculated. The amount of acid consumed and the ash percentage of lignin recovered from gas injection processes was less than the non-injection method. In addition, the oxygen-carbon dioxide injection method showed higher efficiency compared to the carbon dioxide injection. FTIR results demonstrated a similar chemical structure in the recovered lignin. AFM and SEM images of lignin produced by pretreatment with carbon dioxide injection showed larger particles as well as higher thermal stability compared to oxygen-carbon dioxide injection.

Due to the environmental problems of formaldehyde gas emission, governments, manufacturers and scientific societies are looking for a solution to replace urea-formaldehyde adhesive by non-formaldehyde one for wood composites. So, this research was conducted on the feasibility of using old corrugated container fibers and tannin improved soy flour-based adhesive in green fiberboard production. For this reason, Tannic acid (as hydrolysable tannin) by 10 wt% was used as a modifier for soy adhesive and old corrugated container fibers were used in 0, 25, 50 and, 75 wt% based on the dry weight. The results of FTIR showed the chemical bonding between tannin ingredient and soy amino acids by forming a possible covalent bond. Also, the results showed that the physical and mechanical properties of manufactured raw fiberboard did not meet the EN 622-5 standard. Moreover, results indicated that this type of fiberboard needs more investigation, especially in the dry process. These manufactured boards have good potential to be used as a core material in wall and roof sandwich panels without any formaldehyde emission but more improvements are needed in physical and mechanical properties.

Wood modification with cell wall modifiers change the practical properties of wood. Likely, changing the modification conditions with chemicals by different reactivity has a more favorable effect on wood properties. This research was conducted to determine the effect of cell wall modification with glycidyl methacrylate (GMA) and maleic anhydride (MA) on practical properties of wood polymer composite. Test samples were divided into ten groups; control, impregnated with styrene, and combined modification of cell wall (GMA and MA) at four concentrations of 10, 20, 30 and 40%/styrene. Cell wall modification, with increase in weight and conversion rate, improved hydrophobicity and dimensional stability of specimens which for GMA was more than MA. With increasing of the GMA concentration from 30 to 40% and cell wall bulking, cracks probably formed in the cell wall that increased water uptake and dimensional changes. The presence of monomer along with modification, by reducing the polarity of wood, uniform distribution of monomer in wood, and improving the adhesion between polymer and wood, increased the mechanical properties of composites, which showed the highest improvement in GMA/styrene. Modification with MA and GMA prevented the fungi mycelium development through reducing hydroxyl groups, changing the hollocellulose structure, and the presence of polymer as a physical barrier. The effect of GMA combined with monomer created more improvement on biological resistance up to 20% concentration, and by increasing the concentration to 40%, it did not show a significant difference with MA. The mechanical properties improvement can be attributed to the formation of polymers with excellent performance and the effect of modification on the cell walls. In most properties, the effect of GMA up to 20% concentration was more than MA, but with increasing concentration and possibly the appearance of cracks in the cell wall, the efficiency of MA modification was higher than GMA.

In this study, the fibers contained in the medium density fiberboard wastes were recycled using a digester. These fibers were then used to produce cellulose nanocrystals. Morphology, chemical structure and resin residues on fibers were investigated. The acid hydrolysis method was utilized to production cellulose nanocrystals. The properties of nanocrystals made from virgin and recycled fibers were investigated. The results showed changes in the morphology and chemical structure of the recycled fibers. The fibers recycled using digester had better quality as compared to the recycled fibers using conventional recycling method (using autoclave). Elemental analysis showed that after recycling, resin residues remained on the fibers. Due to the shorter duration of heat treatment and the elimination of mechanical separation and better quality of recycled fibers, it can be said that the utilization of digester considered as an efficient method for recycling medium density fiberboard wastes. Investigation of nanocrystalline cellulose properties showed that there was no difference between nanocellulose produced from virgin and recycled fibers and the recycled fibers can be well utilized to production of cellulose nano crystals.

Today, several modeling methods have been used to cost-efficiently predict the physical and mechanical properties of wood-based panel products which in turn reduce the cost of quality control of these products. Two common methods include regression and artificial neural network (ANN). In this study, the possibility of predicting the modulus of rupture (MOR) and modulus of elasticity (MOE) of particleboard by simple and multiple linear regression and ANN based on structural parameters including density in three levels (0.65, 0.7, and 0.75 g/cm3), slenderness ratio of particles in three levels (47, 30, and 13) adhesive percent in three level of (8, 9.5, and 11%) were evaluated. experimental and predicted data were compared with different criteria including mean absolute percentage error (MAPE), mean squared error (MSE) and coefficient of determination (R2). The results revealed that although both multiple linear regression models and artificial neural network were able to predict MOR and MOE values with acceptable accuracy, but ANN model predicted them with higher R2 and lower MAPE than multiple linear regression model. The value of MAPE and R2, for prediction of MOR and MOE by ANN model were 7.72% and 0.77, and 7% and 0.86, respectively. the corresponding value for multiple regression model were 8.3% and 0.738, and 9.06% and 0.783, respectively. These levels of error are industrially and practically satisfactory for the prediction of properties in particleboard.

In this study, the effect of using maleic anhydride and oxidizer (dicumyl peroxide) in improving the properties of composites made of polypropylene and cellulose nanocrystal was investigated. Then, the mechanical, and morphological properties of these composite products were explored. Tensile strength increased with increasing cellulose nanocrystal, but it decreased slightly while 5% of cellulose nanocrystal were added. Due to the addition of maleic anhydride and oxidizer, the mechanical properties of the composite product were reduced which was not expected. Analysis of the contact angle of the samples also showed a decrease in wettability behavior due to increased use of nanocrystalline cellulose as well as maleic anhydride and dicumyl peroxide.