مجله تحقیقات علوم چوب و کاغذ ایران
سال سی و ششم شماره 3 (پیاپی 76، پاییز 1400)

In this study, the quality of Calotropis procera cellulose in 14 ecotypes (Hormozgan province: airport, Tazian, Isin, Soro, Hajiabad, Tang Zagh, Ganj, Abmah, Qutbabad, Gnu, Minab, Gahkam; Fars province: Qalatouyeh and Bushehr province) was investigated to evaluate the plant potentials in the natural habitat and its use in breeding and domestication programs. Samples were selected and collected at the flowering stage in June and July 2017. In this study, the extraction and separation of holocellulose and alphacellulose as well as fiber dimensions in terms of fiber length and diameter, cell cavity diameter and cell wall thickness were investigated. Concerning the cellulose quality, among the 14 ecotypes, the highest amount of holocellulose and alphacellulose was in Hormozgan-Abmah ecotype (54.59%) and Bushehr-Heydariyeh ecotype (61.1%), respectively. Comparison of mean fiber dimensions showed that the highest fiber length was in Minab (0.81) and Tazian (0.78) ecotypes. Also, the highest fiber diameter, cell cavity diameter and cell wall thickness were 34.87, 23.58 and 5.64 microns in the Isin ecotype, respectively. In general, the results showed that due to the suitability of fibers and its high percentage of cellulose, this species can be comprehensively studied for use in industry. Considering that our country has few wood resources and on the other hand, this species has a good growth in the arid southern regions with low water resources of our country, it can be considered as a wood source in the cellulose industry and widely cultivated.

The mechanical (tensile strength and modulus, bending strength and modulus), humidity (water absorption and thickness swelling) and biodegradability properties of wood-plastics produced from polypropylene and poplar wood-flour (wood flour in three levels of 0, 20 and 25 percentage) in the presence of starch powder (at four levels of 0, 5, 10 and 15 percentage) are assessed as a bio strength agent. The material mixing process is run in two stages of applying an extruder machine and applying an internal mixer haake machine. The mechanical and humidity tests specimens are produced by mold injection method and the biodegradability test specimens are formed by hot press method. The tests are run according to standards and procedures. The results indicate that an increase in weight percentage of wood-flour in the composition, increase the mechanical strength, water absorption, thickness swelling and biodegradability of composites. An increase in weight percentage of starch powder in the composition, increase the bending strength and modulus, tensile modulus, water absorption, thickness swelling and biodegradability of composites, while decreasing the tensile strength. Additional studies run through the scanning electron microscopy indicate that by adding wood-flour and starch powder to the composition, the intensity of biodegradation increase at the surface of the specimens. By adding starch powder to the composition, the starch powder particles fill the cavities in the composite structure, thus a reduction in the volume of the pores in the composite structure.

Natural disasters and the need to facilitate and relief the consequences of such disasters has initiated global crisis in its respective management. Reducing the variabilities of inhabitants requires the integrated system to battle against such devastations and crises. This research presents the application of Delfi method to identify the influential factors on risk management model risk management model for the wooden structures in Iran. The statistical population of the study consisted of the academic and organizational experts. A total of 30 individuals were interviewed using a purposive non-random sampling technique as well as data adequacy and saturation principle. A semi-structured interview was used to collect the required data. Delfi method was applied for data analysis in qualitative section. The results indicated that 43 risk factors are influential in wooden structures which can be classified as internal and external risks. Among these risk factors, 11 are considered as the major factors which influences the application of risk management in construction of wood structures in earthquake prone regions of Iran.

In this research, Fir wood (Abies spp.) was thermally modified by retification process. The effect of modification process on physical and mechanical properties of fir wood were evaluated. For this aim, fir wood specimens with 12% moisture were modified in the steel tank with nitrogen gas medium at different temperatures (180 °C, 200 °C, and 220 °C) and 15 hours holding time. Physical properties such as wood density, volumetric swelling, dimensional stability and mechanical properties such as modulus of rupture (MOR), modulus of elasticity (MOE), shear and compression strength parallel to grain and impact strength of different modified wood specimens were evaluated. Results showed that by increasing treatment temperature, during modification process, water absorption and volumetric swelling were decreased and dimensional stability was improved. Also, results revealed that the mechanical strength of modified wood such as MOR, MOE, shear and compression strength parallel to grain and impact strength were decreased.

The aim of current research was to investigate the effect of hydro thermo-mechanical treatment and also press conditions on the physical and mechanical properties of poplar wood (Populus deltoides). The wood blocks were initially treated hydrothermally at temperatures of 100°C for holding time of 0, 60, 120 minutes. Afterwards, the densification process was carried out under a hot press at two phases 1- contact and 2- compression press, for temperature of 160, 180 and 200°C for 60 and 90 minutes. The wood compression set was adjusted for 40 percent based on the thickness (radial direction) of the blocks. The samples were physically and mechanically tested as density, springback after press, water absorption, thickness swelling, bending strength and modulus of elasticity. Afterward, the results were analyzed based on a complete randomized design (CRD) under a factorial experiment. Results revealed that physical and mechanical properties of samples were enhanced due to the combined hydro thermo-mechanical treatment. Results revealed that this process causes reduction of springback, water absorption and thickness (radial direction) swelling and also improvement of mechanical properties such as bending strength and modulus of elasticity.

Growing industrial trees is one of the solutions to overcome the wood resources lack. Thus, for efficient investment in wood cultivation, some cases such as annual growth of cultivated species, species adaptation to the climate of the region, adaptation to the soil of the culture site and also the quality of the produced wood and its capability as a raw material used in lignocellulosic industries, must be regarded. One of the recently introduced extremely fast growing poplar cultivars is the “Mofid” hybrid poplar (Populus euphratica Oliv. × P. alba L.). Since the wood and wood-waste produced during the wood mechanical conversion, are used as the main source in the wood-plastic composite production, in this study, the use of 4-year-old Mofid” hybrid poplar wood-flour as filler in the polyethylene wood-plastic production was investigated. Results indicated that the composites with Mofid poplar lignocellulosic filler had acceptable mechanical and physical properties, in a way that they were comparable with the composites containing hardwoods wood-flour filler (control treatment). Results showed that the plasticity and irreversible-strain during applying force were less in poplar filler-composites, so the tensile and flexural moduli were higher than control composites. Results indicated that the use of poplar wood-flour reduced the impact resistance value. Also, among the treatments of 20, 30 and 40% filler, the 30% filler treatment had the highest mechanical properties. All samples had acceptable water-absorption and thickness-swelling characteristics.

Concerns about environmental pollution caused by petroleum-based packaging materials waste have increased the motivation to research and study on biodegradable packaging materials. In this study, in order to make added value and reprocess of the recycled papers, cellulose nanocrystals were produced from them and added to the hydroxypropyl methyl cellulose / cationic starch nanocomposite in amounts of (3%, 5%, 7%, 9% and 11%) and their structural, strength and barrier properties were investigated. The yield of crystalline cellulose nanoparticles produced from this alpha cellulose was about 65% and according to the (TEM) test results, the obtained nanoparticles were rod-shaped and had a length of 100 to 150 nm and a diameter of 15 to 30 nm. Also, their degree of crystallinity was 79.6% according to the X-ray diffraction test. According to the results, with the addition of cellulose nanocrystals to the nanocomposites, the tensile strength, moisture absorption resistance, and oxygen permeability resistance were increased and only the strain to the breaking point (Flexibility) was decreased and the best strength properties and barrier properties of the nanocomposites were obtained in the presence of 9% cellulose nanocrystals from recycled papers.

One of the problems of non-destructive tests in the detection of the inhomogeneities in wood and wood products is their location relative to the vibrating node and antinode. Thus, the hidden inhomogeneities located at the vibration node in such materials may not have any effects on the dynamic modulus of elasticity and may not be detectable. In this study, we investigated the development of simple end-to-end joint in oak beams (Quercus castaneifolia) with dimensions of 72×4×2 cm (longitudinal×Radial×Tangential), with blocks removed from the areas of 0.06 and 0.50 cm of the beam length. The blocks were removed from the same beam as the joint was developed. The results indicated that developing a joint in 0.50 cm of the beam length has no significant effect on values obtained from the dynamic modulus of elasticity while creating this joint in 0.06 cm of the beam length has a significant effect on values obtained from the dynamic modulus of elasticity. Also, in both joints, the damping and acoustic converting efficiency values were increased and decreased, respectively. The amount of these changes was more in the area of 0.06 cm of beam length. In general, it can be said that due to the effect of vibrating node and antinode and on the other hand, the location of the joint in both areas, the acoustic conversion efficiency factor is a suitable factor to estimate the location of the joint or the inhomogeneity itself.

The plasma has different effects on the surface wettability of wood, depending on the treatment conditions and the type of gas used. The hdrocarbon gases usually destroy hydrophilic groups on the surface of wood and cause hydrophobicity by creating microscopic rough structures. In this study, glide plasma treatment with methane was used to hydrophilize the surface of the wood and create weathering resistanc. The poplar wood (Populus deltoides) were exposed to glide plasma under various laboratory conditions such as time of exposure, voltage, frequency, distance between electrodes as well as flow of inlet gas and outlet gas with methane inside a reactor. Then the surface properties of wood were studied using scanning electron microscope (SEM), measurement of water drop contact angle, ATR‐FTIR spectroscopy, roughness survey, and colorimetry. The specimens were then subjected to the accelerated weathering using the Gardner weathering wheel and their properties were checked again. The SEM images showed that the plasma creates a warty layer on the surface of the wood which could be due to the deposition of new materials or the physical effects of plasma (surface etching). The plasma treatment significantly increased the contact angle of the water droplet on the surface of the treated samples. The treated samples had a higher surface roughness than the control samples. The surface of treated samples was generally darker than the control. After exposure to the accelerated weathering, the effect of treatments on surface hydrophobicity was largely lost. The treated samples had less roughness changes than the control after exposure to the weathering, and also their dark color changed to silver-gray. The use of glide plasma with methane gas showed the great potential for creating hydrophobic surfaces on the wood, but it did not last long and lost its effectiveness due to weathering.

The paper aims to study differential, dynamic-mechanical and biodegradability analysis of polylactic acid/wood fiber (PLA) composites using three levels of nano-graphene (0.75, 1.5 and 3%). In order to mix the materials together and to make standard specimens, an internal mixer and pressure press were used. In the analysis of differential polishing calorimeter, the addition of fibers as well as nano-graphene had a positive effect on the glass transition temperature and the degree of crystallinity, which indicates a change from softness and flexibility to hardness and hardness. Dynamic-mechanical analysis has shown that the addition of wood fibers to pure polylactic acid can case an increase in the storage modulus of the composite and with the addition of nano-graphene to increasing composition, while the highest amount of storage modulus was related to polylactic acid composites / 30% of fibers and 30% of fibers. Results of tan δ peak showed that with the presence of wood fibers and nano-graphene, the temperature was transferred to a higher temperature and the limited movement of molecules due to the improvement of the fiber reaction in the PLA polymer. The results of biodegradability test also showed that the addition of fibers to pure PLA caused a significant increase in the weight loss of the composite. Additionally, nano-graphene to PLA composites decreases with the less weight in composites.