IRANIAN JOURNAL OF WOOD AND PAPER INDUSTRIES
Year:2019 | Volume:9 | Issue:4 |Papers Count:12

Vibration is one of the most important problems in the field of forestry with a chainsaw. The purpose of this study was to measure the vibration of the chainsaw on the hands and arm of sawmiller while cutting the trees in the educational and research forest of Kheyroud located in Mazandaran province. Two alder, Persian ironwood, and poplar trees, which have different densities, were selected and vibration was measured using the SVANTEK vibration instrument, simultaneously in three directions, i. e. x, y and z. For the evaluation of motor vibration, the averaged vibrational vibration index (aeq), total ahv shaking averaging, vibration transmission coefficient (TR) and daily exposure time (A8) were used. It was shown that the mean value of the vibration equivalent of aeq in all three axes (x, y, z) of Persian ironwood is more than poplar and alder species and is significant in all three species in the x direction. The results of Duncan's test showed that there is a significant difference between the three axes (x, y, z) in Persian ironwood and there is a significant difference between x and z in the poplar and alder species and direction y with direction x and also with z direction (P <0. 05). The results also showed that the total vibration of the ahv, motor vibration transmission (Tr) and the daily exposure period (A (8)) in the bin of Persian ironwood is more than poplar and alder species. Due to this difference, it is possible to increase the density, decrease the moisture content and the diameter of the Persian ironwood tree. Therefore, the sawing worker during the cutting of the Persian ironwood is exposed to more vibrations and is likely to develop white-handed disease, which implies the need to observe safety tips, ergonomic principles, and shorten the working hours of a chainsaw worker.

In this study, the alkaline pre-extraction followed with soda and monoethanolamine pulping of barley straw was investigated. The pre-extraction stage with removal of 34 percent hemicelluloses due to highest yield was selected as the optimum treatment. The results of pulping showed that pre-extraction stage resulted in a decrease of yield in both pulping processes meanwhile only in soda process, the kappa number was influenced with pre-extraction stage. Tensile and burst indices of pulps dropped because of pre-extraction stage. Unlike these indices, the tear index of soda pulp from pre-extracted barley straw was increased. The brightness of soda pulp from pre-extracted barley straw was increased while the pre-extraction stage had no significant effect on brightness of monoethanolamine pulps. The opacity of pulps remains unchanged after pre-extraction.

This study was focused on the preparation of an environmentally friendly nanocellulose based hydrogel in the form of pads. Hydrogels are hydrophilic three dimensional network with crosslinks, which swells in water but don’ t dissolve. In this research nanofibrillated cellulose and Hydroxyethyl cellulose with different ratio (1: 1, 2: 1, 3: 1) were used to make hydrogel. Also, citric acid which has a significant advantage over other crosslinking agents in terms of toxicity and price, has been used in different amounts of 10% and 20% by weight to crosslink. In order to find optimal hydrogel preparation conditions, FTIR analysis, FESEM, time dependent swelling measurement and evaluating the thermal and rheological properties were performed. Samples with a lower ratio of nanocellulose to hydroxyethyl cellulose were found to be inappropriate due to the loss of their apparent integrity in the swelling measurement. According to FTIR results, cross-linking were performed only in samples with the highest ratio of nanocellulose to hydroxyethyl cellulose in different amounts of citric acid. Therefore, the hydrogels' characteristics were mainly influenced by the ratio of nanocellulose to hydroxyethyl cellulose and the amount of citric acid had less effect on these properties. These two successful final samples showed acceptable properties in other evaluated properties and led to the selection of optimal reactive ratios for the preparation of hydrogels for use in various industries, including the pharmaceutical industry.

The purpose of this study was to measure the amount of quality decrease in the hornbeam (Carpinus betulus) wood after three periods of four months storage (12 months) in the forest and compare it with the beginning of the period and identify the destroying fungi that appeared. This research was carried out in Shastkolah forests in Gorgan. 15 Billets with 30 cm diameter class and length of 220 cm were cut from a hornbeam tree and stored inside the forest under the same conditions and in contact with soil. The billets were cut at 50 cm intervals at each stage and physical and mechanical properties were measured based on conventional methods and according to related standards. The white rot fungi Sterium hirsutum (Willd. ), Trametes gibbosa Fr., and Trichaptum biformis Fr. were identified on the billets. According to the results, with increasing storage time in the forest, all physical and mechanical properties, except water absorption, decreased. The maximum and minimum changes in physical properties were related to the percentage of water absorption and basic density, respectively. Moreover, the maximum and minimum changes in mechanical properties were related to impact resistance and modulus of elasticity, respectively.

This study examined the effect of targeted subsidies policy on the demand for raw and semi-processed wood (Russian wood, MDF Melamine, MDF Higlass, Chipboard, Litron and door cover) in khorramabad city during the period of 2009-2016. The data of the present study was compiled seasonally from spring 2009 to winter of 2016 by documentary type and from the seven wholesale offices of this city and analyzed using the almost ideal demand system (AIDS). The results showed that the purposefulness of subsidies had a structural failure due to the demand pattern of wood and wood products. In other words, the demand pattern of people before and after the targeting of subsidies is different, which means that the reaction of the applicants of each product to its prices, the price of other products and changes in income before and after the purpose of subsidies has changed.

The purpose of this study was to evaluate the biodegradability of composites made from bamboo flour and polylactic acid using physical properties and bio-durability examinations. On the other hand, the effect of the amount and size of the bamboo flour particles on the physical properties and durability of the biocomposites was another objective of the research. The bamboo flour and polymer were mixed up in a counter-rotating twin screw extruder. The biocomposites boards were produced by compression molding method. The samples were cut and evaluated according to the suggested specifications in the ASTM and EN-113 standards. The results showed that the thickness swelling and water absorption of the composites were increased significantly by increasing the amount and size of bamboo flour particles. Also, bio-durability of the samples against the studied three fungi species showed that Gloeophyllum trabeum sharply caused high mass losses in all samples by increasing the amount of bamboo flour, while pure polymer (PLA) had a very high durability against the fungi.

In this study, fracture toughness and internal bonding of OSB made from Poplar (Populus nigra) was studied. For this aim, ratio of UF to MF (20; 80, 40: 60, 60: 40 and 80: 20), mat moisture (11 and 13), press time (5 and 7 min) and the panel thickness (12 and 16 mm) were chosen as variables. Specimens based on Taguchi design of experiments with the array of L8 (4^1 2^3) were produced and fracture toughness and internal bonding were determined following ASTM E399 and EN 319, respectively. Fracture toughness was determined using stress intensity factor and fracture energy. The result of percentage contribution and the variables ranking showed that the most determining factor on fracture toughness is the ratio of UF to MF. The effect of press time on stress intensity and internal bonding and the effect of panel thickness on fracture energy had the least importance. The highest fracture toughness belonged to OSBs made with UF to MF ratio of 60: 40, mat moisture of 11%, press time of 7 min and the panel thickness of 12 mm. The highest fracture energy and stress intensity factor was 2944 J/m2 and 0. 19 MPa, respectively. The optimum treatment was UF to MF ratio of 80: 20, mat moisture of 13%, press time of 7 min and the panel thickness of 12 mm in light of gaining the highest internal bonding (0. 95 MPa).

In this study, the effect of spruce wood surface lamination by film coatings was investigated on the color changes and surface quality of substrate after accelerated weathering. It was done by using a colorimeter (CLE) and confocal laser scanning microscope (CLSM). For this purpose, the surface of spruce wood (Picea abies L. ) was laminated by alkyd, water and solvent based polyurethane coating films using a special adhesive tape of aluminum and carbon fiber. The coated samples were put in the accelerated weathering (QUV) device for 45 days and then changes in the color and roughness due to the weathering were analyzed. The results showed that the coating films and wood surface discolored due to weathering and the minimum amount of discoloration was related to the solvent-based polyurethane (SP), waterborne polyurethane (PW) and solvent-based alkyd (SA), respectively. Also, the results of confocal laser scanning microscope showed that the roughness variations on the wood surface depend on the type of coating and the main factor in surface roughness changes depends on the absorption percentage and the resistance of the coating to ultraviolet radiation. The lowest and the highest roughness at the coating film and wood substrate were found for the samples laminated by the solvent-based polyurethane and solvent-based alkyd, respectively.

In recent years, plenty of studies have focused on the application of cellulose nanofiber to improve the mechanical and physical properties of paper. But, in this research, the effect of lignocellulosic nanofibers produced from recycled old corrugated container as raw material using ultra-fine grinder, was investigated on some mechanical properties and production process parameters of paperboard. TEM images of produced nanofibers indicated that the nanofiber width was in the range of 10-80 nm. Then, various dosages of nanofiber were applied by bulk addition method to the furnish. Eventually, the evaluation of tensile strength revealed that the application of 5% lignocellulosic nanofiber caused more than 50% increase in tensile strength of produced paperboard. However, the bulk addition of high dosages of the nanofiber resulted in a reduction of bending index (bending stiffness), tear index and especially freeness of the furnish.

In this study, the effect of open time and hardener content was investigated on bending strength of finger jointed made of three wood species; beech, fir and poplar. For this purpose, wooden samples with dimensions of 25mm width, 35 mm thickness and 350 mm length were prepared from three species. After three weeks of storage in climate room, in order to form finger joint pattern, samples were cut at the half of length. Then, the finger joint pattern was done in new exposed cross sections of the samples. After that, the joints were bonded with three PVAc glue types; pure, with 10% and with 20 % hardener. The second variable of study was open time that was controlled in two levels of 2 and 4 minutes. The close time and press time were constant which were adjusted on 2 and 30 minutes, respectively. The joints were pressed in a special wooden frame by hand clamp. After making joints, they were stored in climate room for three weeks and then the three point bending test was carried out according to ISO 10983. The results showed that by adding isocyanate hardener up to 20%, the bending strength increases significantly. The longer open time could not improve bending strength. On the contrary, it caused strength dropping in some treats but these changes were not significant. The strength of joints made with poplar wood was lower than beech and fir, although this difference was not statistically significant. Finally, the best condition for making this joint was determined by application of 2 min open time and using 10 % PU resin as a hardener.

Fundamental studies in wood of trees and shrubs can reveal the possibility of their utilization in various applications or lead to create a database of different wood species. Wild service tree (Sorbus torminalis L. ) is a rare and valuable tree species in Hyrcanian and Arasbaran forests. This study investigated some anatomical, biometrical, physical and chemical properties of wild service wood. Wood samples were cut from Sangdeh forests of Mazandaran. Studies showed that wild service tree is extremely compact and dense; its average density is 832 kg m-3 and its shrinkage is about 16%. Growth rings boundaries are indistinct. From anatomical view, it is a diffuse-porosity wood and its vessels are exclusively solitary, long (999 microns), narrow (55 microns) and are not visible with naked eye in transverse section. Growth ring boundaries can be distinguished by only two to three compact fiber layers. Rays parenchyma is heterogeneous, and exclusively 2-seriate (partially uniseriate). The fibers are of vascular tracheid type with an average length and cell wall thickness of 1575 and 9. 33 micron, respectively. The content of cellulose, lignin, extractives and ash were 49. 8, 18. 9, and 2. 3 percent, respectively. Preservation of valuable tree species of the northern forests such as wild service tree should be on the agenda of natural resource custodians.

In this study, phenol was partially substituted with urea to reduce the production cost of phenol formaldehyde resin (PF), and a new resin phenol-urea-formaldehyde (PUF) was synthesized. Different formulations of resin PUF with different molar ratios were made using different methods. The structure of the formulated resins and their coagulation behavior were evaluated with infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC), respectively. FTIR and DSC analysis indicated the best results for the synthesized PUFB3 which was made from phenol, urea, and formaldehyde with a molar ratio of 1: 0. 5: 1. 7, respectively, and exhibited a similar methylene structure with PF resin. Then, the formulated resins were applied to produce particleboard. Mechanical properties of the produced particleboards were determined and compared with those of ones which were prepared with PF resin as the control treatment. The findings demonstrated that the substitution of urea increased the dry internal bonding strength and modulus of elasticity but reduced the internal binding strength of the produced particleboards following a two-hour immersion into boiling water. The findings revealed that the mechanical properties of the particleboards produced with PUFB3 resin were comparable to the control treatment, and the formulation of phenol, urea, and formaldehyde with the molar ratio of 1: 0. 5: 1. 7 was selected as the optimum treatment for outdoor condition and under load. In addition, the particleboards produced with PUFD1 resin which was formulated of phenol, urea and formaldehyde with the molar ratio of 1: 0. 5: 2. 5 exhibited standard properties for application in outdoor conditions without load.