مجله صنایع چوب و کاغذ ایران
سال دوازدهم شماره 1 (بهار 1400)

In this study, the effect of different levels of nano-SiO2 particles and film thickness on physical properties of acid catalyzed and nitrocellulose transparent coatings applied to beech and spruce wood was investigated. Nano-SiO2 particles were added to coatings in order to improve adhesion characteristics and wettability behavior. For this purpose, specimens were prepared to dimensions of 220 ×80 ×20 mm. Nano-SiO2 particles were prepared at concentrations of 0, 0.5, 1 and 2 wt% and added to the acid catalyzed and nitrocellulose transparent coatings. To study the effect of different levels of film thickness on adhesion characteristics of nano coatings, specimens were coated at two levels of thickness of 60 µm and 120µm using film applicator. According to ASTM D 4541 standard, the adhesion strength of specimens was determined. Scratch resistance was determined according to ASTM D 3359. According to ASTM D 5946 standard, contact angle was measured. Results revealed that the highest adhesion strength was obtained in beech species coated with acid catalyzed containing 1% nano-SiO2 particles with thickness of 60 µm. Increasing the nano particles up to 2% had negative effect on adhesion characteristics.The increase of the film thickness decreased adhesion characteristics significantly. The increase of nano-SiO2 particles, up to 2%, increased the contact angle of the surfaces of specimens significantly. Thus the incorporation of nano-SiO2 particles into coatings, up to 1%, improved adhesion characteristics and the incorporation of nano-SiO2 particles into coatings, up to 2%, improved the wettability behavior of coatings. Furthermore applying films with lesser thickness led to increase of adhesion characteristics.

This study aimed to evaluate cellulose nanofibers and study the effects of these material on starch sizing as the most commonly used sizing in historical paper relics and its use as strength enhancer to restore tensile strength and durability. This research was conducted by analytical comparisons method and samples were collected by experiments related to research topics such as pH measurement, calorimetric and the measurement of tensile strength of the samples. In this study, treatment of cellulose nanofibers with weight percentages of 0.5, 1 and 2%, was prepared as a suspension with water and used to treat the samples containing starch sizing and without it. The results showed that the tensile strength of non-sizing and starch- sizing samples increased after treatment but after aging, the tensile strength of the samples containing starch- sizing decreased slightly. The highest tensile strength after treatment was observed for samples containing starch sizing with 2% treatment at 36 Nm/g and after aging, for non-sizing samples with 2% treatment at 28.2 Nm/g. PH value of non-sizing samples after treatment ranged from 6.98 to 7.17 and after aging, it still remained within the neutral range of 6.85 to 7.11. pH of samples containing starch sizing after treatment was within the neutral range from 7.36 to 7.42 and after aging also remained within the range of 7.16 to 7.19. Examination of the color changes of the samples showed that after treatment of non-sizing and starch- sizing samples, the color of the samples is brighter. After the aging, the color of both groups of samples became darker and it tends to yellowing. However, the color changes in the samples containing starch sizing was less than the non-sizing samples.

These days, researchers in all fields are looking to develop new products using new technologies including nanotechnology. The objective of this study was to evaluate the performance of selenium nanoparticles in the paper coating formulations in order to improve the antibacterial, physical and mechanical properties of paper. The paper was coated with selenium nanoparticles with concentrations of 100 and 200 ppm accompanied by cationic starch. The paper surface coated with nanoselenium particles and starch has been characterized using ATR-FTIR and SEM. The results have showed that selenium nanoparticles had a good effect on inhibiting the growth rate of both Staphylococcus aureus and Escherichia coli. At equal consumption levels, the growth rate of Staphylococcus aureus decreased more than that of Escherichia coli. The growth rate of Staphylococcus aureus bacterium in the control and nanoselenium 200ppm coated paper specimens were 91.93% and 8%, respectively. Density and thickness of the paper sheets increased in the paper coated with cationic starch and nanoparticles in comparison with uncoated paper. Water absorption and water vapor Transmission Rate in nanoselenium coated samples were lower than starch coated samples and coatings had a significant effect on the rate of resistance to air in the paper. It is also seen increasing concentration of nanoparticles had no significant effect on the burst and tear indexes.

The date palms of southern Iran are exposed to one of the most dangerous termites in the world, Microcerotermes diversus Silvestri (Isoptera: Termitidae). Therefore, in order to evaluate, control and limit the activity of this termite, the resistance of palm wood impregnated with different concentrations of Kraft black liquor (30, 20, 10 and 40%) against termites attack was evaluated in laboratory (selective and non-selective test) and field conditions. Due to the special structure of palm wood anatomy, the results showed that the treatment of specimens with black liquor solution was an effective method in slowing down termite activity. Observations also showed that as the concentration of lignin in the impregnating solution increased, the desirability of wood for termites decreased, although no significant difference was observed between the 30 and 40% concentrations. Finally, FT-IR spectroscopy of black liquor showed the presence and effect of sulfate groups on reducing food desirability.

In order to investigating the usage of wheat straw on particleboard, wheat straw powder was treated with 5% hydroxide sodium for 120 minutes; then, untreated and treated wheat straw powder were mixed with industrial wood chips in five levels of 0:100, 30:70, 40:60, 50:50, 60:40, 10%, and 12% urea formaldehyde resin based on dry weight of raw materials, and 2% ammonium chloride based on dry weight of adhesive to make single layer particleboard. Physical and mechanical properties of produced panels were tested according to EN 326-1 standard. The physical and mechanical properties of panels made from treated wheat straw were significantly better than untreated one, and use of 40% wheat straw powder with alkali treatment ratio to industrial wood chips was shown the best results.

Since the life of a tree strongly depends on sapwood area activity, the detection and thickness measurement of sapwood area in living trees are important for forest scientists. However, determination of sapwood zones has various challenges in different species. In this research, the electrical impedance tomography was applied to calculate sapwood-heartwood ratio and electrical impedance variations in the given area in one of the most important softwood species (Pinus nigra). A GeoPic-32 multielectrode resistivity meter with some modifications, was used to measure electric impedance distribution in two heights of 147 and 200 cm of 8 pine tree cross sections in Sopron of Hungary. For providing tomograms, a 5-voltage electrical current was conducted among installed electrodes. The impedance value maps on the studied cross sections were also measured by a resistometer device. The tomography map showed that the role of sapwood area for electricity conductivity, compared with heartwood, was more pronounced. For all achieved tomograms, three zones with different colored pattern were detected. The red colored parts surrounding pith area had the highest values while the minimum resistivity values with the dark blue color, were recorded for area near the bark.  9 percentage difference in moisture content between sapwood and heartwood, pH variation (4.52˃3.88) and consequently different quantities in chemical components affected electrical properties distribution in cross section of trees. But potassium content had no pronounced effect on tomogram patterns obtained.  Finally, this technique is suggested to evaluate trees in forest because of facility, shortening of time, and minor destruction as well as no necessity to cut the tree.

Juniper trees are the native conifers of Iran extends in large areas of the country and is a factor to prevent soil erosion. However, the problem of Iranian juniper forest is the lack of natural regeneration. Therefore, the purpose of this study was to investigate the regeneration status of juniper plants in Jeyshabad (North Zanjan) repository at different times by using of Dendrochronology. In order to do this research, two plots were identified randomly in the protected and grazing areas, and samples were taken from all trees in each plot using increment borer. After preparing sample surface, ring width of the trees were measured and cross- dated. The results showed that the number of trees in the protected area is more than the grazed one. The mean diameter at breast height (DBH) of the trees in the protected area was lower, but in terms of average age, they were older than the trees in the grazing one. In the protected area, the number of trees in the age group of 10-20 years was remarkable, which showed that it had regenerated in the last two decades; while in grazing area, regeneration was affected and no new trees were observed after the period 1986. It was concluded that grazing decreased the regeneration of juniper and the growth pattern of the trees also changed; in a way that does not follow the form of natural growth.

The increase in population has led to the production of large amounts of agricultural wastes that pollutes the environment. Today, the use of agricultural wastes to extract cellulose and nano-cellulose is increasing. In this study, cellulose and nanocrystalline cellulose were extracted from three types of palm waste, including fibers, leaves and palm clusters and used to identify cellulose and compare it with pure cellulose SigmaAldrich from devices using FTIR, TGA and XRD. Cellulose extraction yield was measured at 25% in palm fibers, 20% in green leaves and 33% in clusters. The FTIR and XRD spectra of isolated cellulose was similar to pure cellulose and the degree of crystallization was in order of leaf > fibers > clusters. The loss of weight for all cellulose samples in TGA charts at 350 oC was similar to that of pure cellulose and the nanoparticle length range of these cellulose was determined by the FE-SEM electron microscope 20 to 36 nanometers.

In this research, the effect of cold plasma treatment on coating ability of palm trees for bark cutting pattern was evaluated. For this purpose, the date palm trunk with an average diameter of 60 cm was selected and discs with a thickness of 5 cm were prepared from the height equal to the pollen chest. Then, healthy and flawless samples with dimensions of 10 × 10 cm were prepared from three points: close to the bark, between bark and center of the trunk and near the center of the trunk. Before the tests, the surface of the samples was sanded and then conditioned. After cold plasma treatment and then coating with acrylic water-based paint, surface roughness, wettability and adhesion of coating were done on samples. Based on the results, the highest base density and the lowest surface roughness were observed near the center of the trunk. The results also showed that plasma treatment increases the surface wettability. According to the inverse relationship between surface roughness and adhesion, before and after plasma treatment, the highest and lowest tensile adhesions were observed near the center of the trunk and near the skin, respectively. It can be concluded that the use of plasma treatment improves the adhesion of the palm tissue.

In this study, in order to improve the physical and mechanical properties of fluting paper from a mixture of old corrugated containerboard and bagasse soda pulp, cationic starch and based on pretests, was used in three levels of 5,10 and 15 kg per ton of paper and with a control sample, ie Paper without cationic starch was compared. The results showed that the effect of cationic starch in different treatments on grammage and tensile index was not significant, and was significant on burst and tear index and also CMT. Using cationic starch up to 5 kg per ton of paper can be effective in improving some physical and mechanical properties of fluting paper, such as reducing porosity and increasing burst index, but consuming more will not only not improve the paper's strength properties, It also reduces some of the resistance properties, especially the corrugated medium test. In addition, consuming more cationic starch will incur additional costs and increase the final price of the product.

The aim of this study was to investigate the effect of coating Populus nigra with silica nanoparticles on some performance parameters. Wood samples of P. nigrawere were coated with a combination of silica nanoparticles (3%, 5% and 7%) and zycosil by spin coating method and the obtained results were compared with controls of A. alba and P. nigra. Structural properties of wood samples were investigated by SEM and FTIR tests. Performance properties of wood samples, including water absorption, contact angle and density were investigated. The results showed formation bonds between silica nanoparticles and zycosil. Coating wood samples with silica nanoparticles in the concentrations of 5% and 7% in combination with zycosil decreased water absorption compared to P. nigra control (P<0.05). The wood samples coated with nanosilica and zycosil had a higher contact angle and density compared to P. nigracontrol (P<0.05).

Investigation about antibacterial papers has been attracted much attention. In this study, antibacterial papers were produced by treatment with chitosan, zinc nano oxide (Zno) and their composition. In the first stage, chitosan was used in 1.5, 2.5 and 3.5% and Zno in amounts of 0.5, 1.5 and 2.5%. Then, the optimum amounts of materials were determined according to bacterial response, and the paper was produced by the combination of chitosan and Zno. The strength, optical and antibacterial properties of the papers were investigated. The results showed that the tensile strength of the chitosan and Zno composite increased. The brightness and opacity of the papers decreased and increased, respectively. Also, the antibacterial performance of the papers on the E. coli and Staphylococcus aureus was good and prevented to the growth of bacteria.

Acoustic tomography technology is a non-destructive method that can reveal the hidden defects of trees. As a result, the aim of this study is to detect the internal defects of the oak tree (Quercus castaneifolia) using acoustic tomography. For this purpose, samples were randomly prepared from ten trees in the Asalem region of Gilan province and then discs were cut from trunks. Doe to the lack of natural decay, artificial cavities were drilled inside the disks in four stages: 25% - 50% - 75% - 100%.  Healthy and defective samples were obtained and the sound wave velocity was calculated using FAKOPP Microsecond Timer device. The results show that the average speed of sound waves passing through the oak wood is 1500 meters per second, which decreases greatly with increasing internal defects. If internal decay progresses from 25% to 100%, the amount of reduction in the speed of sound waves varies from 15% to 36%. The size of the crack or shake is also effective in reducing the speed of sound waves. In large shakes, the speed of waves was reduced by more than 50%. The speed of waves is different in the sapwood and the heartwood. Tomographic images are green in the healthy parts, yellow in the primary decay, and orange and red in the decay, and blue in the cavity parts. Generally, The Acoustic Tomograph accurately revealed the presence and magnitude of the defect without differentiating between decay and crack.