مجله تحقیقات علوم چوب و کاغذ ایران
سال سی و هشتم شماره 3 (پیاپی 84، پاییز 1402)

 The purpose of this study was to evaluate effectiveness of brown rot fungus on ash (Fraxinus Sp.) and spruce (Picea Sp.) thermo-wood and also thermally modification on fungal functionality. In first step, prepared wood samples of both species were heat treated under 212 ºC for 3 hours. Afterwards, heat-treated and untreated wood specimens were exposed to brown rot fungus for 16 weeks based on EN 313 and the functionality of fungal destructive agent and also its effect on physical and mechanical properties were finally analyzed. The obtained results showed that the brown rot fungus has been more efficiency on untreated specimens in compared with thermo-wood in both two wood species and caused more destruction and mass loss. Moreover, the results revealed that some physical and mechanical properties include density, compression parallel to grain and impact strength of exposed heated specimens to brown rot fungus were more than unexposed heated specimens to this fungus. Evaluation of laccase activity which produced by brown rot fungus showed more its effect on controls than heat treated specimens in both wood species. Based on the results, thermally modification can generally causes improvement of biological resistance, reduction of some physical and mechanical properties as well as more stability of applied properties of ash and Picea wood which exposed to the brown rot fungus.

Biological protection is one of the rather new and environmentally friendly methods of wood protection, in which living microorganisms have replaced chemical substances. This research was carried out with the aim of investigating the biological protection of beech wood against the white rot fungus (Trametes versicolor) using Trichoderma harzianum. For this purpose, the antagonistic ability of Trichoderma against wood rotting fungus was evaluated in dual culture medium as well as on wood. Trichoderma was incubated on wood samples in two time periods of four and eight weeks, and then samples were exposed to white rot for 16 weeks. The dual culture test proved the antagonism of Trichoderma against wood-destroying fungi, in a way that after 14 days, Trichoderma had not only prevented the spread of T. versicolor hyphae, but also overgrew on its mycelia. Cellulase enzyme assay showed that this isolate of Trichoderma had little ability to secrete this enzyme, and for that reason, sample weight loss due to fungal treatment was neglectable; a result that was also confirmed by infrared spectroscopy. The duration of wood incubation with Trichoderma was an important factor in the efficiency of treatment: increasing the time by one month significantly reduced weight loss of treated samples from 15% to below 1%, while the weight loss of the control samples was more than 30%. It can be concluded that the long-term treatment of beech wood with Trichoderma does not have a destructive effect on the wood and protects it against the white rot. Therefore, it is suggested to use this type of biological agent as a pretreatment of beech wood or to combine it with other preservative materials.

Fibre-gypsum board is a composite, in which fiber used as the reinforcement in the matrix of gypsum. The purpose of this article is to investigate the effect of different amounts of waste paper fibers on the strength, resistance and the fracture behavior of fiber-gypsum board. For this purpose, amounts of zero, 5, 10, 15, 20, 25 and 35 percent of waste paper fibers have been used. The results of measuring bending strength, internal bonding and moisture absorption during one month exposure to 100% relative humidity show that increasing the percentage of fibers up to 20% has increased the mechanical properties. In general, By using twenty percent fibers the bending strength increased fifty percent and the internal bonding became double and half in comparison to the control samples. The load-displacement curve shows that an increase of 5 to 15 percent of fibers does not change the fracture behavior of the fiber-gypsum board and they had brittle fracture same as control samples. While in more substitution values, the flexibility increases and the failure becomes ductile. Therefore, the best conditions in terms of strength, resistance, and flexibility have been obtained in 20% replacement of gypsum with waste paper fibers.

This research was conducted with the aim of investigating the effect of two-layer coating of nano-polyurethane and nano-clay on the mechanical and physical properties of packaging cardboard with brown layer. For this purpose, brown layer cardboard with grammage of 127 was prepared and tested. To coat the surface of the cardboard, it was first coated with nano-polyurethane and sprayed by a coating nozzle. Then the surface of the brown layer cardboard was covered with nano-clay to improve the performance of the coating material of the first treatment. Nano-clay coating was performed by a laboratory coating machine called barcoter. The coated cardboards were restrained and dried in the room for one day to stabilize the coating material on their surface. Then the samples were placed inside the freezer for 2 and 4 months and their properties were measured. The results showed that coating reduced water absorption. In the coated and frozen samples, an increase in thickness, smoothness of the surface and a decrease in water absorption and resistance properties compared to non-frozen control samples have been observed. Double coated samples showed very few pores. The thickness, smoothness of the surface and resistance to tearing in the machine cross direction of the double coated brown cardboard showed an increase of 13.7%, 75% and 3.8%, respectively, compared to the control sample. water absorption, resistance to bursting, resistance to tearing in the machine direction, resistance to tensile in the machine direction, resistance to tensile in the cross machine direction, resistance to ring crush test in the machine direction and resistance to ring crush test in the cross machine direction of the double-coated brown layer cardboard compared to the control sample, showed 107.20, 1.5, 34.3, 25.4, 24.3, and 4.7 percent decrease respectively.

The walnut tree is one of the most important species in Europe, Asia and Iran, which is used in various industries such as furniture, veneer, and construction due to its high resistance and beauty. In this research, walnut trees from two different geographic locations, one from the forests in the north of Iran (Noor) and the other in the west of Iran (Shahrkord), were selected. We studied physical properties including dry density, basic density, shrinkage, and mechanical properties including bending strength, modulus of elasticity, compression parallel to the grain, shear, tensile parallel and perpendicular to the grain, tangential and radial screw withdrawal strength and toughness. In this research, standards 3129 and ASTM D143-14 were used to perform physical and mechanical tests, respectively. The moisture content of all samples during mechanical tests was 12%. The average dry density of Noor and Shahrekord walnuts was 0.61 and 0.57 (g/cm3) respectively. The results of variance analysis showed that the characteristics and physical resistances of these two species were not significantly different except for dry density, radial, tangential and volumetric shrinkages. However, due to the higher density of Noor species, it showed higher mechanical resistance compared to the Shahrekord species.

Development of active and biodegradable packaging is possible by coating biopolymers on packaging materials. In this research, in order to improve the mechanical and barrier properties of polycaprolactone polymer films, cellulose nanocrystals obtained from alpha-cellulose of cotton linter were added to the poly caprolactone composite solution with amounts of (3%, 6%, and 9%), and their structural, mechanical, and barrier properties were investigated. According to the results of the field emission scanning electron microscopy (FESEM) test, the obtained nanoparticles are rod-shaped and have a length in the range of 100 to 150 nm and a diameter of 10 to 50 nm. X-ray diffraction (XRD) confirmed the formation of cellulose nanocrystals. According to the results, by adding cellulose nanocrystals to the composite solution, tensile strength, resistance to water solubility, and impermeability to the water vapor of the films increased, and only the elongation at break reduced. The best mechanical and barrier properties of the nanocomposites were obtained in the presence of 6% cellulose nanocrystals.

The aim of this study was accomplished on identification and comparison of the phenolic chemical components in wood of Siberian elm, Common elm and Mountain elm tree. For this purpose, the samples were chosen randomly from of elm trees in Nowshahr's forest region. Then, flour and ash were provided from these woods of species (separate) by TAPPI standards. After samples prepared, samples were injected to the GC/MS device for it analysis. Identification of compounds was done by retention time of each compound, calculation of Quats index and Adams table. The result of GC-MS showed that there were 116, 41 and 18 compounds in wood of Siberian elm, Common elm and Mountain elm tree, respectively. That 5-Hydroxy-calamenen (21.23%), 1-Naphthalen carboxylic acid (15.41%), Naphthalene (0.96%) and phthalate (1.00%) were the most important ‎ compounds in wood of Siberian elm. The 5,6,7,8-tetrahydro-2,5-dimethyl-8-(1-methylethyl)-1-Naphthalenol(18.59%), Gamma-Sitosterol (13.44%), bis (2-ethylhexyl) phthalate (12.28%) and 1-Naphthalen carboxylic acid (5.73%) were the most important ‎ compounds in wood of Common elm, too. There were the bis (2-ethylhexyl) phthalate (93.40%), 4-(N-Isopropylamino)-6-phenyl (1.89%), 5, 6, 7, 8-tetrahydro-1-naphthalenol (1.80%) and 8-methoxy-1-acetonaphthone (0.27%) as the most important ‎ compounds in wood of Mountain elm tree. In addition, the results showed that 9,12-Octadecanoic acid, Hexadecane, Dodecan, Tetradecan, 1-Naphthalen carboxylic acid and bis (2-ethylhexyl) phthalate were the 6 common compounds in the wood of Siberian elm and Common elm tree. There were the Qoinindolin, Tetradecan, Hexadecanoic acid and bis (2-ethylhexyl) phthalate were the 4 common compounds in the wood of Siberian elm and Mountain elm tree. There were the Tetradecan, Hexadecanoic acid and bis (2-ethylhexyl) phthalate were the 3 common compounds in the wood of Common elm and Mountain elm tree, too. The gas chromatographs showed that Tetradecan and bis (2-ethylhexyl) phthalate were the 2 common compounds in three spices of elm trees.