مجله تحقیقات علوم چوب و کاغذ ایران
سال سی و پنجم شماره 3 (پیاپی 72، پاییز 1399)

This study was carried out to investigate the effect of Bagasse alkaline treatment (hydroxide sodium) on Medium Density Fiberboard (MDF) properties. For this purpose, wet depitted and storage bagasse was used. Cooking process was done for fibers preraring in 10 liters digester. Liqure to bagasse ratio was 10 to 1. Hydroxide sodium content was 0%, 4% and 5% based on oven dry weigth of bagasse. Cooking time and temperature were 5 min and 170 centigrade respectively. Fiber slides were obtained by using optical microscope. Chemical components such as holocelloulose and lignin contents were determined. Liqures pH was mesearued before and after cooking. Urea formaldehyde resin was used for MDF producing. Resin content was 12% based on oven dried bagasse. Bending properties (MOR & MOE), internal bonding and thickness swelling of the boards were determined based on EN-310, EN-319 and EN-317 respectively. The results showed that when using 4% alkaline treatment, were seen the minimum fibers cutting and crusing. With increasing of hydroxide sodium content, lignin content decreased and holocelloulose increased. Bulk density increased when increasing hydroxide sodium content. The maximum MOR, MOE and internal bonding of the boards were obtained in 4% hydroxide sodium content. Also thickness swelling of the boards was minimum.

The aim of this study was investigation of the performance of mitered corner joints (L-shaped) reinforced by fibers reinforced polymer (FRP) at maximum stress area under diagonal compression loading. In This way, structural performance of constructed corner joints of two species of beech and fir reinforced by fiber reinforced polymer at polymeric matrix of epoxy with one and two layer of carbon and glass fibers and were investigated. After construction of the mitered joints with wooden dowel and polyvinyl acetate adhesive, the joints were reinforced with FRP composites and then were subjected to diagonal compression loading. Results have indicated that reinforcing layers prevent joint opening, however, failure was occurred at the joint by peeling fibers from wood surface or members fracture near the joints by stress concentration. The results of variance analysis showed that the independent effect of species of joint members and numbers of fibers layer were significant at 95% confidence level. The results showed that use of beech wood in comparison with fir wood, composites reinforced by carbon fibers compared to glass fibers, as well as the use of two layers of fiber compared to 1 layer of fibers, exhibited better performance in constructed joints. The joints made with beech wood and reinforced with 2 layers of composites reinforced by carbon fibers showed the best performance under diagonal compression loading.

Mineral fillers are the second most important elements used in papermaking. Increasing filler content in writing and printing papers without decreasing the mechanical properties is always desired for enhancing the optical and printing properties and cost effective papermaking process. In this study, to increase the filler content in paper, calcium silicate was loaded by in situ precipitation on bleached bagasse fibers. The effect of reaction temperature on the loading and precipitation of calcium silicate on fibers was investigated using ash content measurement, XRD spectroscopy, SEM imaging and EDX analysis. Finally, the effect of treated pulp content on the physical and mechanical properties of pulp was investigated. Ash measurement results showed that calcium silicate precipitation in bleached bagasse fibers was achieved and the amount of calcium silicate loading increased with increasing the reaction temperature. XRD spectroscopy confirmed the formation of calcium silicate and calcium carbonate, and their precipitation in cell walls, lumen and interior spaces of the bleached bagasse fibers was confirmed by SEM imaging. The precipitated minerals on the fiber surface consisted of particles with various diameters. The EDX analysis confirmed the presence of silica and calcium in the treated fibers. With the constant basis weight of 80 g/m2, brightness and apparent density increased significantly, however the paper strength decreased by increasing the content of treated fibers in handsheet paper.

The aim of this study was to solve the environmental problems caused after the bleaching of bagasse pulp by hypochlorite sodium in Pars paper mill. For this purpose, ECF bleaching method was used by performing OQPDEP sequence. The properties of bleached paper were compared to the bagasse unbleached paper as control and some paper properties that made from bagasse bleached pulp by EH sequence in Pars paper mill. The results showed that increasing the bleaching time of bagasse pulp from 30 to 120 minutes by oxygen had no significant effect on paper brightness, but paper density, burst and tear indices decreased. Pulp bleaching by O1QP3D(EP) sequence compared to bagasse unbleached paper led to the paper brightness of about 75% ISO that is about 5% ISO more than the Pars commercial bleached paper. Paper strengths were similar to Pars commercial paper made of soda bagasse and the national standard of Iran (ISIRI 4120). Soda pulp bleaching using O1QP3D(EP) sequence has led to acceptable physical, optical and mechanical properties in addition to environmental benefits such as reduce pollution. So, it is recommended to replace the current bleaching method of Pars paper mill by the mentioned sequence.

Abstract In this research, the effect of cellulose nanocrystals on the functional properties of wood cement composite panels has been investigated. Variable factors in this research are the percentage of nano in (five levels of 0, 0.1, 0.2, 0.5 and 1%), the weight of cement and also the ratio of mixing wood chips with cement in three levels (1 to 3, 1 To 3.5 and 1 to 4) dry weight of cement. In this research, poplar wood and Portland cement type 2 have been used as fixed agents. In total, 15 treatments and 3 replicates of each treatment were made. Preparation of sample in accordance with the standard (DIN / EN 634) and measurement of physical and mechanical properties including flexural modulus, modulus of elasticity in accordance with the standard (DIN / EN 310), internal adhesion in accordance with the standard (DIN / EN 319), thickness swelling after 2 and 24 hours of immersion in water was performed according to the standard (DIN / EN 317). Increased cellulose nanocrystals improved physical and mechanical strength. SEM microscopic images were taken from the samples to examine the microstructural properties of the composite. In the pictures, it was found that by adding cellulose nanocrystals, we see an improvement in the disintegration of nanocomposite materials and as a result, an increase in mechanical and physical properties.

The aim of this study was accomplished on identification and comparison of chemical compounds in heart wood and bark of mulberry tree. For this purpose, the samples were chosen randomly from heart wood and bark of mulberry tree in Nowshahr's forest region. Then, flour and ash were provided from heart wood and bark of mulberry tree by TAPPI standards. For measured metallic ions, first the mineral compound of ash dissolved by 65% nitric acid and for its identified by atomic absorption method. The results showed that zinc ion in heart wood of mulberry tree was more than its bark, but manganese and iron ions were lower and its cupper ion was same. Then extractives were separated from wood flour by acetone and extractives residue transferred to glass vial and was added BSTFA reactive agent to it. 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 are 30 compounds in bark of mulberry tree, that beta-Tocopherol(40.86%), bis (2-ethylhexyl)phthalate(11.2%), 9,12-Octadecadienoic acid(9.12%) and Triphenyl phosphine(9.82 were important components. 93 components identified heart wood of mulberry tree that resorcinol(79.47), methyl diphenyl methane(12.06%), p-xylene(0.06%) and gibberllin A3 (0.15%)di-limonene, as important components. These compounds can very important in durability and consumption its. Comparison of chromatograms showed that 1,2-benzenedicarboxylic acid was exists as a common components in heart wood and bark of mulberry tree.

The aim of this research was investigating the effect of fiber reinforced polymer (FRP) on the strength of T-shaped wooden joints under tension load. In this regard, T-shaped joints were constructed with beech and poplar species and were reinforced with 1 and 2 layer of carbon and glass fibers reinforced epoxy and vinylester polymers of composite. Joint members were assembled by used of wooden dowels and polyvinyl acetate adhesive and then withdrawal resistance of reinforced joints were studied. Results of variance analysis showed that the independent effect of species of joint members, resin type and number of fiber layers at FRPs was significant at 5% level. Results have indicated that withdrawal resistance of joints constructed with beech species was more than the poplar species. The investigation of the effect of number of layers showed that the withdrawal resistance of the joints reinforced by two layers of carbon and glass fibers was more than one layer. Results of FRPs investigation indicated that use of epoxy matrix in comparison with vinyl ester matrix exhibited better results. In addition, carbon fibers have shown better performance than glass fiber as reinforcing agents. According to the results the best treatment was the joints of beech wood and reinforced by composites with epoxy matrix and reinforced with two layers of carbon fibers.