مجله صنایع چوب و کاغذ ایران
سال دوازدهم شماره 4 (زمستان 1400)

In this research, the physical and mechanical properties of the surface sizing liner papers with starch formulation with soda and formacell lignins have been investigated. The soda and formacell lignins from the remaining black liquor were separated and then was replaced with anionic starch in 30, 50, 70, and 100 ratios. In addition, 0.3 g/m2 alum as a cationic agent was charged to the suspension. The results of this study show that even by 100 % replacing starch with both types of lignins, the physical characteristics (air resistance, cobb, coarseness) and mechanical properties of surface-sized paper have been improved compared with control paper. According to the results, 50/50 lignin/starch ratio improved the mechanical and physical properties better and was determined as optimum level. For soda lignin without alum, tensile (36.21 N.m/g) and burst (1.58 Kpa.m2/g) indices increased by 55 and 35 % respectively, compared with the control in the optimum level. For formacell, lignin/starch in 50/50 ratio without alum, the tensile and burst indices were increased 47 and 27% respectively, compared with the control sample. According to the results, it is possible to replace at least 50% of starch with the above-mentioned lignins, which will play an important role in food security and add value for pulp mills.

Noise pollution is one of the most important physically harmful factors in work environments in developed and developing countries. In this study, the measurement of sound emission in the cutting process of Iranian native woods and the ergonomic evaluation of the use of protective earphones have been investigated. Three wood species of alder, sycamore, and hornbeam with equilibrium moisture of 12% and Folder Remote Cutting Machine was used to evaluate the level of noise pollution in the machining process. Also, a digital sound level meter (Benetech GM1356) was used to evaluate the sound. The results showed that with increasing the specific gravity of wood, the amount of sound emission increased; that the highest frequency of sound was observed in alder wood. The results showed that in general, with increasing parameters such as the number of blade rotations, kerf, blade diameter, feed rate, use of the scoring blade, and increasing the service life of the saw blade, the number of sound emission increases. However, the use of saw blades with more teeth saw blades with expansion slot, and the use of rip fence in the wood cutting process reduced sound emission. Also, the results showed that the use of protective earphones is very useful in noise pollution and reduces the amount of sound emission up to 38 decibels. Based on the findings of this study, it can be concluded that the amount of wood density changes in native species of Iran is one of the main factors in the amount of sound emission and the use of protective earphones reduces possible damage due to noise pollution in the cutting process.

One of the disadvantages of recycled fibers is the significant loss of mechanical strength of the paper due to the decrease in the bond between the fibers. The objective of this study was to investigate the effect of adding paulownia nano-wood on the improvement of pulp from old corrugated containers (OCC). Therefore, in this study, with the aim of preserving the mechanical properties of paper, a nano wood-cationic starch system was used. The pulp was prepared from OCC collected and after refining and obtaining a flow rate of 380 ± 20 ml, different amounts of nano-wood (1, 2, and 3%) and cationic starch (0.5, 1, and 1.5%) was added to it. Finally, standard hand sheet papers were made from these treatments, and their physical and mechanical properties were measured according to the TAPPI standards. The results showed that the density and air permeability increase with the addition of cation-starch nano-wood in the paper. Also, the results showed that there is a significant difference with 95% confidence between different treatments in terms of mechanical strength. The highest values of burst resistance index (2.173 kPa / g), crush resistance in ring mode (177.4 N), and air passage resistance (36.9 s) belonged to S3N 1.5 treatment. It can be concluded that the use of larger amounts of nano-wood with the help of cationic starch as retention aids improves the final paper strengths.

The import of wooden ice cream sticks to Iran has always been criticized due to the existence of domestic factories. In this study, the type of wood used in imported ice cream sticks to the country was identified and some of their qualitative characteristics were investigated in hope that the results will be used by domestic producers. Classic (flat) and round ice cream sticks were obtained from Daity, Mihan, and Kalleh ice cream manufacturers. The results of wood identification showed that birch is the most used wood in making ice cream sticks, followed by beech. In terms of contact angle, surface roughness, and wood extractives, sticks made from beech wood (round Mihan) were different from other woods, but in sensory evaluation tests, round samples of Mihan and Daity, regardless of their wood type, received the highest scores. According to the results, the optimal properties of woods to be used as ice cream sticks were discussed.

In the current research, enzymatic modification of OCC pulp with Bacillus sp. amylase was evaluated. Amylase was added at different levels of 0.5, 0.1, 0.2 and 0.3% (based on oven-dried weight of recycled paper) to OCC pulp under constant conditions included consistency of 10%, temperature of 50°C, time duration of 1 hour, and at a pH range of 6.9-7. To neutralize the residual enzyme, hydrogen peroxide 0.05% (based on oven-dried weight of pulp) was applied. The refining of pre-treated OCC pulp with different levels of amylase was done at the constant revolution of 2000. The dewatering and physical properties of amylase pre-treated OCC pulps as compared to control pulp (non-treated pulp with enzyme) for two refined and unrefined conditions were evaluated. Obtained results showed that amylase pre-treatment improved pulp freeness by 11-22% compared with the control sample. The highest freeness (600 ml, CSF) was achieved with 0.2% amylase. Refining of both amylase pre-treated OCC pulp and the control sample reduced the pulp freeness, but dewatering capability increased with an increase in amylase usage. The use of Amylase resulted in a paper with slightly higher caliper, higher bulk, but similar air resistance, compared with control run. An increase in amylase usage from 0.5% to 0.3% along with refining decreased caliper and bulk and increased air resistance of paper. Also, the results of the evaluation of different times of amylase treatment of unrefined OCC pulp (at a constant concentration of 0.1%) on a caliper, bulk as well as air resistance indicated that the duration of 90 minutes was the optimal time. In general, the combined treatment of amylase (0.05-0.1%) and PFI refining (at the constant revolution of 2000) indicated the pulps with better quality in terms of dewatering and physical characteristics in comparison with control OCC pulp.

Due to the lack of forest resources, the use of fast-growing wood species has been considered by designers and engineers. Low density and mechanical strength are the main challenges of using some of these wood species, especially in the manufacturing of construction products and their final properties. Using different methods such as hydrothermal and hygrothermal treatments combined with compaction techniques can be a solution to this problem. This study aimed to investigate the effect of pretreatment type and densification conditions on the physical and mechanical properties of paulownia (Paulownia fortune) and poplar (Populus deltoides) wood. For this purpose, pretreatment with water at 25˚C and compression in hot press at 160˚C, and also pretreatment with steam at 160˚C and compression in cold press at 60C˚ were used. Compression was performed at two levels of 25 and 50 percent for 20 minutes in a press with a pressure of 5MPa to reach a final thickness of 2cm. Then, the equilibration of the samples in the cold press was performed to reduce the spring back and reach the temperature and equilibrium moisture content. To investigate the physical and mechanical properties of the samples, tests including density, water absorption, and thickness swelling (after 96 hours of immersion in water), modulus of rupture, modulus of elasticity, impact strength, and hardness were performed. The results showed that the poplar wood has better physical and mechanical properties than the paulownia wood due to its higher density. Except for thickness swelling, desirable physical properties and higher mechanical strengths were obtained in wood samples modified by the steam-cold pressing method. The greater impact of the wood modification process by steam-cold pressing on the properties was well observed. Water absorption and thickness swelling values of wood samples increased with increasing compaction percentage. The mechanical properties of wood had shown a decreasing trend, with increasing compaction and consequently increasing the density of wood samples, except for impact resistance

The main purpose of this study was to evaluate the effect of densification process on the surface characteristics and bonding quality of poplar wood. For this purpose, the specimens were treated by hygrothermal treatment and then were densified by hot press. Some properties of treated specimens such as surface contact angle and surface roughness were evaluated before and after planning. Moreover, the shear strength of glue line and also delamination of specimens in soaking-drying and boiling-drying cycles were investigated. The results of the poplar wood densification revealed that the surface roughness of the specimens reduced and surface contact angle increased by hygrothermal pre-treatment. The results also showed the positive effect of combined hygrothermal and compression treatment on the delamination after soaking-drying and boiling-drying cycles. In addition, the shear strength of glue line reduced by applied combined treatments. In addition, microscopic images showed that this process changed the physical structure of the surface.

Conversion of renewable and sustainable materials to valuable products is a known way to replace synthetic polymers with natural polymers. lignin is a bio-renewable material and it is the second most abundant biopolymer from biomass. In this work, lignin-based hydrogel was synthesized by crosslinking reactions between dialdehyde cellulose and aminated lignin. Lignin was subjected to amination by Mannich reaction and cellulose was oxidized by sodium metaperiodate, which has been confirmed by FTIR spectroscopy too. The FTIR spectroscopy of the produced hydrogel showed that aldehyde groups of oxidized cellulose react with the amino groups of aminated lignin through a Schiff base, which provide the successfully crosslinking for construction of a hydrogel network. SEM revealed a porous architecture of hydrogel with different pore size distributions. The surface Properties of hydrogel was determined by BET analysis, which indicated the internal porosity of the hydrogel. The results confirmed that the aminated lignin-based hydrogel prepared in this research is a sustainable green hydrogel, which would be beneficial for different applications.Conversion of renewable and sustainable materials to valuable products is a known way to replace synthetic polymers with natural polymers. Lignin, bio-renewable material, is the second most abundant biopolymer from biomass. In this work, the lignin-based hydrogel was synthesized by crosslinking reactions between dialdehyde cellulose and aminated lignin. So lignin was subjected to amination by Mannich reaction and cellulose was oxidized by sodium metaperiodate, which has been confirmed by FTIR spectroscopy results. The FTIR spectroscopy of the produced hydrogel showed that aldehyde groups of oxidized cellulose react with the amino groups of aminated lignin through a Schiff base, which provides the successful crosslinking for the construction of a hydrogel network. SEM revealed a porous architecture of hydrogel with different pore size distributions. The surface properties of hydrogel were determined by BET analysis, which indicated the internal porosity of the hydrogel. The results confirmed that the aminated lignin-based hydrogel prepared in this research was a sustainable green hydrogel, which would be beneficial for different applications (hygiene, agriculture, etc).

The aim of this study was to improve the joints of the mitered furniture frames by using the densified poplar dowels (Populus alba) instead of beech dowels. Therefore, the effects of the dowel number (one and two dowels), dowel diameter (8, 10, and 12mm), and compression ratio (0, 15, and 30%) on bending moment capacity of L-shaped frame corner joints constructed of medium-density fiberboard (MDF) under diagonal tension load were investigated. Then, their performance was compared with those manufactured with beech dowels. Polyvinyl chloride (PVA) was used for gluing the joints. Diagonal loading was performed by Hounsfield (model No. 0380) testing machine with a 5 mm/min loading rate. The results revealed that the bending moment capacity of joints was increased 105.5, 54.3, and 28.75% respectively with the increase of the dowel number, dowel diameter, and compression ratio. The highest bending moment capacity was observed in the joints made out of two 30% compressed dowels with a diameter of 10 mm, and the least of them were seen in joints constructed of one uncompressed dowel with a diameter of 8 mm. the comparison of the joints dowelled by poplar with beech showed that the difference among the bending moment capacity of joints made of poplar dowels with 30% compression ratio and beech dowels was very small (less than one percent), which indicates usability of the densified poplar dowels instead of beech ones.

By considering the high consumption of acoustic panels in the related industries and the importance of natural fibers’ consumption as proper sound absorber replacement for synthetic fibers, the probability of producing acoustic panels made of date-palm-trunk fibers and sodium silicate adhesive is assessed. The effect of thickness, density, particle length, adhesive percentage and air-gap on sound absorption coefficient are measured according to ASTM 10534-2 ISO at 250, 500, 1000, 2000 and 4000 Hz frequencies. The results reveal that an increase in thickness shifts the sound absorption coefficient peak towards lower frequencies. An increase in density increases the sound absorption coefficient and at high frequencies it decreases. An increase in particle length increases sound absorption coefficient and at 4000 Hz this process is reversed. An increase in adhesive percentage decrease sound absorption coefficient at high frequencies. The effect of 25 and 41 mm air-gap on sound absorption frequency on the best produced panels of 32 and 16 mm thick, respectively, is assessed.  Panels of low thickness at higher air-gap enhance sound absorption coefficient at all frequencies. This fact can be highly contributive in reducing production cost of environment-friendly acoustic panels where, silicate sodium adhesive is consumed.