IRANIAN JOURNAL OF WOOD AND PAPER INDUSTRIES
Year:2011 | Volume:1 | Issue:2|Papers Count:9

In this research, dry shell formation and receding of evaporation front through the thickness of beech and spruce boards were investigated during drying using X-ray spectroscopy.Four surfaces of the boards were coated using epoxy resin to limit moisture flux through the board thickness. The boards were dried using a convectional drying method under the temperature of 60oC and relative humidity of 70%. The scanning process was conducted once in an hour during drying until the dry shell reached the core layer of the boards.The results revealed that the dry shell was formed faster in the beech board in comparison with the spruce one; however, it reached the core layer of the spruce board in a shorter time.In addition, the pattern of dry shell formation was found to be different between the boards; a steady-state condition as a result of faster bulk flow of free water was observed during the early stage of drying of the spruce board.In general, it can be concluded that the controlling factor in the dry shell development to the core layer is water vapor diffusion coefficient of the boards rather than their permeability.

In order to establish a kiln drying schedule for Poplar (Populus nigra) lumbers of 5 cm thickness commercially cut from Taleghan region, three schedules, namely T8-F4, T8-F5 and T9-F4 were adopted to dry the lumbers to the final moisture content of 11±2%. Dry bulb temperatures for the schedules were adjusted at 54, 54 and 60oC, while the final drybulb temperatures were adjusted at 82, 82 and 71oC, respectively. The severity of surface, internal checks and warp in the lumbers were measured before and after the drying process and quality control methods were used to analyze wood defects. Results indicated that drying of Poplar lumber using each of the three schedules was satisfactory; however, the third schedule (T9-F4) resulted in better drying quality than did the others. Also, equalizing of lumbers for 24h is recommended.

In this research the effect of heating pretreatment and non-simultaneous addition of chemicals in hydrogen peroxide bleaching of CMP pulps was investigated. Before the bleaching stage by hydrogen peroxide, Q stage was applied by means of removing transition metals from pulps by using of DTPA pretreatment under the same condition for all pulps. For this purpose, unbleached mixed hardwood CMP pulp was used. Hydrogen peroxide bleaching operation was done with three different procedures including: adding bleaching chemicals simultaneously, adding bleaching chemicals non-simultaneously and adding bleaching chemicals with heating pretreatment at two hydrogen peroxide levels of 2 and 3% and in NaoH/H2O2 proportions of 0.8 and 0.7 with 3% sodium silicate at 70oC for 150min at 10% consistency level.Results obtained from measuring optical and physical properties of handsheets showed that in all treatments at the same peroxide charge, non-simultaneous addition of chemicals with pretreatment (process 3) caused better improvement in brightness and density of the paper. Also opacity, yellowness and caliper were lower in this process than the others. To reach a given brightness, hydrogen peroxide can be decreased. Therefore, by using the modified bleaching process we can economize on consumption of chemicals, by decreasing peroxide and alkali consumption at 1% and 23.8% to reach a given brightness. Also, COD load in this process at both levels of peroxide was lower than the other processes and therefore, it may decrease environmental contamination and effluent treatment requirement.

Important importers of wood, paper and their products were identified in this study. Identification of these countries is important for the trade of wood and paper products. The main questions now are: how is imports situation of wood, paper and their products in the world? And which countries are important here? Average values and percentages of imports were calculated to rank regions on the basis of FAO stats from 1998 to 2007. The annual rates of change in imports were calculated by single payment formula and the positive correlation of import prices was determined by coefficient of determination. Our results showed that imports of products frequently had increasing trends in the study period, and they had stable markets with low fluctuations. China and Germany were the most important countries with France, Italy, Japan, Canada, Belgium, Holland, Austria, South Korea, Mexico and Denmark ranking next for these products. Wood and paper products of Asian countries were developing faster than other continents. Import efficiency of paper and wood products of Iran is low due to their high added value. Political developments after 2001 and increasing energy prices resulted in increase in products price worldwide with trends being increasing with high coefficients of determination (R2).

This study was aimed at determining the effective criteria for location selection of wood drying plants in Iran. For this purpose, after review and field visit of the industries, 35 key indicators were identified. These criteria were divided into five major groups as: materials, infrastructure, technical, economical and instructional indices. The priority rates of these criteria and sub-criteria were evaluated by AHP technique. The results indicated that among 35 effective sub-criteria in location selection of the plants, the sub-criteria of quality of raw materials (0.152), purchasing raw materials, land cost, profitability, reliability of supply, and sales had the highest priorities, which were rated as 0.118, 0.105, 0.067, 0.061 and 0.057, respectively.

In the present study, the potential use of zycosil and clay nanomaterials was examined to decrease water absorption of Medium Density Fiberboard (MDF). For this, a group of MDF samples were coated by nanozycosil and in the other group, nanoclay was used to produce the MDF. Then, water absorption and thickness swelling of the MDFs were evaluated. In order to characterize the structure of the MDF, X-ray diffraction (XRD) and SEM observation were performed. The results of different tests indicated a desirable effect of nanozycosil on water resistance properties of MDF. Nanozycosil reduced water absorption by 90% because it could modify MDF surface by reacting with the board thereby imparting a molecular level hydrophobic characteristic. Regarding the effect of nanoclay, the scanning electron microscope (SEM) images and X-ray diffraction (XRD) confirmed a suitable dispersion and exfoliation of nanoclay in the modified MDF. The water absorption presented a decrease with increasing nanoclay content. The nanoclay had no effect on the thickness swelling.

In this paper, regarding the high capability of polymeric composites as a substitute of the wood in musical instruments, the acoustic properties of carbon fiber-polyester composites, such as elastic modulus, acoustic coefficient, acoustic coefficient efficiency etc, were investigated using free longitudinal and flexural vibration non-destructive tests and forced vibration non-destructive test. For better understanding, three wooden samples of poplar, walnut and beech trees (frequently used in the manufacturing of musical instruments) were chosen and analyzed. Comparing the results showed that the resultant composites had essential acoustic and vibrational properties higher than those of wood samples. Ultrasonic velocity and elastic modulus in longitudinal direction of carbon composites were approximately 11300 m/s and 130GPa, respectively. Besides, the damping results of carbon composites are magnificent and far better than those of the wood specimens.

In this study, the effect of two lignin mixing methods on physical and mechanical properties of wood flour- polypropylene composites was investigated. Kraft lignin was extracted from black liquor by acidic method and was mixed with wood flour by physical and chemical methods with ratios of 2, 5 and 10 percent (based on wood flour dry weight). The composites were produced by hot press method after mixing of wood flour, lignin and polypropylene at presence or without MAPP. The physical and mechanical properties of prepared samples were measured according to standard methods. In general, the results showed that adding lignin to composites decreased water absorption in both methods. Also increasing lignin from 2 to 10 percent increased impact strength of composites with or without MAPP. Flexural strength of the composites differed depending on mixing method.Increasing of lignin decreased flexural strength of the composites without MAPP in the physical mixing method where as in chemical mixing method it was increased. It is to be noted that the composites with 5 percent lignin, made with physical mixing method and with MAPP exhibited higher flexural strength than other composites.

In this paper, the design, construction, and performance analysis of a wood thermal conductivity measurement device using flat plate heat pipes has been experimentally studied. The device was designed to measure the thermal conductivity of wood in various ranges of temperature. Thermal conductivity of hornbeam (Carpinus betulus) has been measured at various temperatures between 40-80oC and a relationship has been recommended for the sample. The results show that the thermal conductivity of this species increases linearly with temperature. Also, it has been concluded that flat plate heat pipes distribute heat flux on the surface of the wood uniformly leading to a faster steady state condition, which can reduce time of the test and result in energy saving and more accurate results.