مجله صنایع چوب و کاغذ ایران
سال یازدهم شماره 3 (پاییز 1399)

Delignification and subsequently densification of wood is one of the newest approaches leads to a considerable improvement in mechanical properties of wood. However, because removal of the hydrophobic lignin, the problem of set recovery is still remained. In the present study, the poplar wood samples were chemically treated with sodium hydroxide and sodium sulfite solution and then were soaked in the solution of glycerol-citric acid; then densification was conducted in a pilot hydraulic press at temperature of 100oC for duration of 24 hours. Set recovery of the densified samples was decreased considerably, however removal of the hydrophobic lignin led to increase of the thickness swelling and anti-swelling efficiency became negative. Results of infrared spectroscopy on the delignified densified samples proved the formation hydrogen bonding between cellulosic units in compressed state which is a good reason for decreasing the set recovery. Surface impregnation with glycerol-citric acid combination led to a considerable reduction of set recovery. The infrared spectroscopy and also the microscopic study showed the presence of polyesters in the microstructure of the densified-impregnated samples.

Wood heating is the oldest method for reducing of water absorption of wood. Today, electric heating is used to transmit high voltage current through materials using two electrodes. The aim of this study is to investigate the effect of electric shock on the physical and mechanical properties of Iranian beech wood( Fagus orientalis L). Electric shock applied to the wood samples in five different voltage and three different pressures in the reactor. The experimental design was a factorial experiment on the basis of a completely randomized design .The results show that electric shock of beech wood improves all its physical and mechanical properties. The best results obtained at atmospheric pressure and electric current of 600 volt.In this situation, Moduli of elasticity became treble and Moduli of Rapture increased 20% based on control sample. Also obtained 20 % Anti-Swelling efficiency.

The purpose of this study was to predict and evaluate the load carrying capacity of double shear connections of hybrids wood products in combination with steel dowel and plates based on European codes (EC5). The main variables were layered hybrids (4 levels), fastener diameter(2 levels) and fastener number in raw (3 levels). For this study, new types of engineered wood products were used in which plywood and OSB were joined together as three-layer structural components by a single component of polyurethane resin. The fastener was steel dowel 6 and 8 mm in diameter and steel plate 4 mm thick. The values of the load carrying capacity of the connections were predicted based on EC5 equations and Johansen failure modes. The test specimens were loaded according to EN 26891 to investigate the effect of the research parameters. The results showed that the effect of the increasing of plywood share especially in the middle layer of the new hybrids was significant on the increasing of load bearing capacity of the joints. Increasing the diameter of the connector from 6 to 8 mm also increases the load bearing capacity of the joints. Also, as the number of pins in the row increases, the load bearing capacity of the joints is increased. The research findings indicate that the formulas provided by EC5 have the ability to predict the strength and behavior of the joints in this study and even in some treatments the experimental values were higher than the predicted values. POLT1 and POLT2 composites in double shear connections have load bearing capacity values close to EC5 predicted values and also more than it. In studying the failure modes of the connections, steel dowels of 6 mm showed better performance.

Regarding the shortage of the wood resources in the country and the increasing trend for using them as constructional materials, densification of planted fast growing species in order to improve the physical and mechanical properties is inevitable. In the present study, poplar wood samples were impregnated with raw and epoxidized soybean oil and densified to the compression ratio of 30%. Heat treatment was used to overcome the set recovery problem. Results of the set recovery test showed that the set recovery values for samples impregnated with epoxidized oil were lower than the ones impregnated with raw oil. Heat treatment decreased the set recovery values to 46 and 63% for raw oil and epoxidized oil impregnated samples respectively. Results of water absorption tests showed that for non-densified samples, impregnation with oil led to lower water absorption which was more pronounced for the epoxidized oil impregnated samples. Generally, water absorption of densified wood was higher than the non-densified ones and heat treatment lowered that. Scanning electron microscopy images and Fourier Transform Infrared Spectroscopy was used for interpretation of the set recovery test results.

In this study, all-cellulose nanocomposite was prepared through partial dissolution-nanowelding of cellulose nanofibers (prepared from Nano Novin Polymer Co.) using ionic liquid and the effect of dissolution time and recycled solvent on nanowelding process and nanocomposite properties was investigated. Also, six times of 5, 10, 20, 30, 60 and 120 min were used as dissolution times to partially dissolve cellulose nanofibers. Results showed that with increasing dissolution time, crystallinity increased and crystallite size decreased. FE-SEM micrographs confirmed that increasing dissolution time led to decrease in nanofiber diameter and increase of welding area. With the increase of dissolution time, tensile strength and Young’s modulus increased. But, these mechanical properties dropped over dissolution time longer than 30 min. However, the longer dissolution time, the higher strain at break. Since all-cellulose nanocomposite prepared with dissolution time of 30 min showed highest mechanical properties, recycled solvent was also used just for 30 min as dissolution time to partially dissolve cellulose nanofibers. The results of this section showed that nanocomposite prepared with as-received solvent had similar properties with that of prepared by recycled solvent.

The use of minerals instead of expensive virgin fibers is one of the common ways to reduce production costs in papermaking. But the presence of fillers reduces the mechanical properties of produced papers. In this study, the possibility of using zeolite (an abundant mineral) as a filler along with chitosan biopolymer was investigated. Zeolite was replaced by virgin fibers at three levels of 10, 20 and 30% (based on pulp dry weight). The results showed that the presence of 1% chitosan as an additive in pulp increased the zeolite retention in printing and writing paper. But the presence of chitosan in the paper containing the filler had no effect on the mechanical properties. It seems that with increasing the amount of chitosan, the mechanical properties can be improved along with improving the fillers retention.

In this research, the effect of palm tissue densification on coating quality was investigated. From the palm trunk, specimens of 5 × 10 cm with thicknesses of 2, 2.3 and 2.5 cm were prepared and put into a conditioning room (T = 25 °C and RH=65% ) for reaching a moisture content of 12%. Densification of samples was performed in three stages: warming, densification and steam treatment. Then, the samples were coated with alkyd, water and solvent based polyurethane and to evaluate properties, colorimetric, roughness and tensile adhesion tests were done. Based on the colorimetric results, the lightness was reduced in all samples by densification. Also, after coating the brightness of the samples decreased and the yellowness and redness of the samples increased. Statistical analysis showed that there is a significant difference in the brightness parameter (L *) between 10% and 20% compressed and control samples with water-based polyurethane coating. The results of roughness test showed that after densification and coating samples, the roughness of all samples was reduced and the best performance for the compressed sample was 10% with the solvent-based polyurethane, which had 4 times less roughness on average than the control sample. According to the results of adhesion test, the adhesion rate increased in all treatments with increasing densification percentage and the highest amount was observed in compressed samples by 10%. In other words, due to the densification and cohesion of the palm texture, the surface roughness decreased and improved by up to 10% of the adhesion resistance due to better penetration of the coating as well as the compressive strength of the fiber in the compressed sample.

This study aimed to the native starch modification with α-amylase enzyme and compare it with oxidized starch for surface sizing of paper. Native starch was prepared under different temperature and time conditions by addition of alpha-amylase enzyme to achieve viscosity proportional to oxide starch for base paper surface sizing. Then, the basic industrial paper was subjected to surface sizing by immersion with enzymatic starch and oxidized starch prepared. The papers physical and mechanical properties were measured and evaluated after drying. Based on the results of this study, oxidized starch viscosity at a concentration of 5 % at 95 °C reached 17.51 cp during preparation and to achieve this amount of enzymatic starch viscosity, native starch was prepared at 85 °C using 0.005 % enzyme. The results also showed starch modification with the enzyme by varying the temperature, cooking duration, and concentration of the enzyme and native starch, it is possible to achieve a spectrum of viscosity. Evaluation of the physical and mechanical properties showed greater improvement in paper properties including indices of transverse and longitudinal tensile strength (20% and 30% respectively), transverse and longitudinal tear strength (7% and 15% respectively), burst strength (15%), CMT (7%), and RCT (30%) using enzymatic modified starch compared to oxidized starch for surface sizing. In general, the use of α-amylase enzyme in comparison with oxidized starch enables the economical preparation of starch with a spectrum of viscosity for different conditions for a certain improvement in paper properties can be considered for industrial application.

This study and it aim was accomplished on the effect of using cellulose nano-fibers and cationic starch on optical and mechanical properties of chemi-mechanical pulp. For this purpose, first some of bleached CMP pulps were randomly selected from Mazandaran Wood and Paper Industries (MWPI) as control. Then, cellulose nano fibers bought as white gel and used in 0, 2, 3 and 4 % levels. The cationic starch were added in 0, 0.3 and 0.6 % levels and imported long fibers with 0 and 5 % levels to CMP pulps suspensions, too. The hand sheets were prepared from above-mentioned of pulps with 60 gr/m2 basis weight and then the optical and mechanical properties were measured and compared according to TAPPI standard test methods. The results showed that brightness, a* factor, tear, tensile, burst strengths and air resistance were increased and opacity and greenness were decreased. The results showed that all optical and mechanical properties expect greenness and burst strength, improved with 5% addition imported long fiber and 3 and 4 % cellulose nano-fibers. The results showed that using 0.6 % cationic starch with 4 % cellulose nano fibers improved the most paper properties, expect brightness and tensile strength, too.

Wood pulp and paper as one of the wood products has undergone many changes in the regional and global market share in terms of production capacity and consumption patterns over the past few decades. Due to the limited domestic resources and the increasing trend of wood consumption and its products in Iran, imports have been considered as one of the most important ways to supply the domestic demand. The main intention of this study is to perform scientific analysis of the paper and paperboard market conditions over the period of 1986 to 2018 using Bound Test. The quantitative value of the impact of studied variables on the amount of paper and paperboard imports was calculated using the estimated short- and long-term elasticity. The results showed that among the studied variables the GDP (without taking into account of oil exportations) with elasticity of 2.16% in the short run and 1.26% in the long run, And the domestic wood production from northern forests with amount of -0.69 and -0.57 elasticity in short and long term, respectively; had the most impacts on paper imports. However, the economic sanctions considered as a new variable in this study resulted in a decrease of paper and paperboard imports with coefficients of -0.50 and -0.41 imports, in the short and long run respectively.

This study was performed to analyze the energy consumption in bagasse production as one of the byproducts from sugarcane and greenhouse gas emissions (GHG) amounts from bagasse production and its bagasse based Medium Density Fiberboard in Iran. Related data for this study was collected by direct interview and filling out questionnaires using company managers and staffs in Karoon Sugarcane Agro-Industrial Company and LooheSabz Jonoob bagasse based MDF Factory for the years 2016 to 2019. Greenhouse gas emissions were assessed by SimaPro software and energy consumptions amounts were calculated by direct and indirect energy consumptions and energy equivalents. Total energy consumptions for bagasse production were 2436.75 and 1368.74 MJ ha-1 in plant and ratoon farms, respectively. Water for irrigation, diesel fuel consumption and nitrogen fertilizer had the largest share of energy consumption in sugarcane production. The total amounts of greenhouse gas emissions for bagasse production were attained as 221.87 and 99.11 KgCO2eq ha-1 in plant and ratoon farms respectively. Diesel fuel consumption, agricultural machineries and nitrogen fertilizer in plant farms and diesel fuel, phosphate and nitrogen fertilizers in ratoon farms had the highest share of emissions, respectively. Furthermore, the amount of greenhouse gas emissions for bagasse based - MDF production was gained as 780.53 KgCO2eq m3-1. Electrical energy consumption, urea formaldehyde resin and natural gas had the main share in total GHG emissions in bagasse based -MDF production.

The aim of this Study was to investigate on the effect of using vegetable oil containing UV absorbent as coating on the weathering resistance of heat treated wood. For this purpose, 180 gr/m2 of vegetable oil (linseed or soybean) containing 0 and 0.5 wt% of UV absorbent (nano ZnO or Tinvin 326) was applied to the surface of the specimens by brush. The weathering resistance of these specimens after six months of natural weathering was examined by colorimetry, roughness, ATR-FTIR spectroscopy and stereomicroscope. The results of colorimetry indicated that in the first month of weathering, coatings containing soybean oil had less color changes than coatings containing linseed oil. But at the end of the weathering, But at the end of the weathering, specimens coated with linseed oil (pure and containing nano ZnO) and soybean oil containing nano ZnO had the least color changes compared to other treatments. The results of the roughness test revealed that the oil coatings have partially reduced surface roughness increasing due to weathering but the UV absorbents did not have a positive effect in this regard. Stereomicroscope images also indicate that coated heat treated wood specimens had less surface degradation and surface crack than uncoated specimens.

Pollution from airborne particles is one of the most important threats to human and environmental health in the world. Today, industrial air filters use synthetic polymers based on oil and chemicals, these materials are incompatible with the environment and lead to secondary pollution. Therefore, the development of the use of new materials in the fabrication of air filters, which is not only environmentally friendly but also renewable, is a vital need. For this reason, in recent years, many researches and studies have been done to replace cellulose nanofiber (CNF) with synthetic fibers such as glass nanofibers, activated carbon, and plastic polymersnanofibers in the manufacture of air filters. CNF has many advantages such as biodegradability, cheapness, low density, and network structure that can compete with synthetic nanofibers. Therefore, this review study aims to investigate the general use of CNF for the adsorption of particulate matter (PM) and carbon dioxide (CO2) in the air. The results showed that CNF increase the adsorption efficiency of CO2 and PM due to the presence of active hydroxyl groups on the surface as well as high specific surface area. In addition, the nanofilters made of CNF have a lower pressure drop than filters on the market due to their small pore diameter.