مجله تحقیقات علوم چوب و کاغذ ایران
سال سی و دوم شماره 1 (پیاپی 58، بهار 1396)

The present research work has investigated the physical and mechanical properties of hygro-thermally modified poplar (Populus deltoides) wood. The poplar wood blocks were treated hygrothermally at temperatures of 130, 150 and 170°C and for 20, 40 minutes as holding time. The physical and mechanical properties were determined for both treated and untreated wood. The properties; mass loss, collapse, specific gravity changes, dimensional stability, surface roughness, bending strength and modulus of elasticity, were determined prior to and after the treatment in all wood blocks. As expected, the hygrothermal treatment significantly improved the dimensional stability of the samples. It was also found that the hygrothermal treatment could increase collapse, surface roughness and modulus of elasticity due to the treatment. However, there were decreases in wood mass, specific gravity and bending strength of the treated poplar wood. It was revealed that the mass loss, decrease in the density as well as collapse in woos is correlated with treatment temperature as well as the holding time. While, raise of the treatment temperature as the holding time caused increase of the dimensional stability.

In this study, 10 samples of beech wood, without apparent defect, with dimensions of 360 × ýý16 × 16 ýcm (length × radial × tangential) were selected, and after being exposed to variable ýtemperature (60, ýý80, 100, 120, 140, 160, and 180°C) and moisture content conditions ýý(moisture content in conditions ýof: saturated with water (EMC=35±5%), equilibrium moisture content ýexposed to air (EMC=19±5%), ýand conditioning moisture content in a climatic chamber (EMC=12±2%), they underwent free ýflexural ývibration test in two longitudinal-tangential and longitudinal-radial planesýþ,þý and some ýof the physical, ýmechanical, and acoustical properties in both planesý were investigated. The ýresults showed that the ýcorrelation coefficient of the first three modes of flexural vibration in ýboth planes under ýclimatic ýchamber had a similar situation, but when the samples were in the ýwater-saturated condition, they ýshowed an adverse behavior in each plane. The effect of ýincreasing the temperature above 100°C ýcaused stresses resulting from shrinkage leading to ýthe development of micro-cracks and reduction in ýthe modulus of elasticity of cell walls and ýultimately reduction in wave propagation ability of wood, ýthus increase in the damping ývibration values in both longitudinal-tangential and longitudinal-radial ýplanes of the samples. ýAlso, the concurrent changes in modulus of elasticity and damping vibration in ýboth vibration ýplanes are a desirable indicator for monitoring the process from the primary logging ýprocess ýstages to processes such as wood drying and heat treatment.ý

Because of importance and wide usage of different species of Populus wood in paper pulping, the delignification reaction in pulping process of P. deltoides was investigated in order to obtain the relation between residual lignin in the pulp and cooking time. The samples were 10 years olded of Populus deltoids woods which were collected from Chamestan Research Station located in Noor city of Mazandaran province. Kraft method was used for pulping the condition of which were 25% sulfidity, 14% alkali, 5:1 the ratio of liquor to sample, maximum cooking temperature as 155, 165, 175 degree centigrade. Kappa number and the yields of pulps were estimated and residual lignin was calculated for each sample. Using the models predicted for rate equation and trial and error method in excell software, the order and rate constant of delignification reaction were evaluated for each cooking temperature. The results show that the rate equations of delignification reaction of Populus deltoides in temperatures of 155°C, 165°C and 175°C have the orders of 5.5, 2.5 , 1 and the rate constants of 1.8× 10-7 min.-1 conc.-4.5, 7.7× 10-4 min.-1 conc.-1.5 and 3.5× 10-3 min.-1 , respectively. Using these equations it will be possible to control the pulping process and predict the time required to obtain a desired lignin concentration in the pulp.

In this research the effect of chemical modification with Polycrease ECR on the functional performance of poplar wood to use as wood polymer were investigated. Polycrease ECR the modified dimethyloldihydroxy-ethyleneurea (DMDHEU) was used for chemical modification of wood by impregnation method. Specimens prepared according to the ASTM standard and treated in two levels of 30 and 50%. Modification process of specimens were performed at 24 hours in temperature of 120°C. Functional performance including Weight percent gain (WPG), bulking, long term water absorption and volumetric swelling in 8 weeks, bending strength (MOR) and modulus of elasticity (MOE), compression strength parallel to the grain, shear strength and withdrawal resistance of screw parallel to the grain was measured. Two-way analysis of variance (ANOVA) was used for statistical analysis. Obtained results of modified specimens were compared with untreated control. Results showed that modification with Polycrease ECR had significant effects on physical and mechanical properties in treated specimens. Chemical modification in 30% level, lead to reduce long term water absorption and volumetric swelling. Reduction in mechanical properties were not considerable. Chemical modification with Polycrease ECR in 30 % level compared to 50 % level, showed better physical and mechanical properties. Generally, influence of chemical modification on the physical properties (long term water absorption and volumetric swelling) were dominant.

At this research, the influence of Multi Walled Carbon Nano Tubes (Non-functionalized and functionalized) on mechanical properties of polypropylene – old corrugated container (OCC) fibers composites was investigated. OCC fibers polypropylene composites were prepared using 20% OCC fibers, 80% polypropylene and 3% MAPP. Three levels of multi walled carbon nano tubes (0% - 0.5% - 1%) were added. Acidic oxidation method was used to functionalize the MWCNTs. Mechanical properties were measured as defined in ASTM testing methods. The results indicated that at higher dosage of MWCNTs, the tensile strength properties of the composite were improved but the influence of the functionalizing was not statisitaclly significant. The bending strength and elasticity as wellas the izod impact were increased as the higher amount of nanotubes were added to the composite. Scanning Electron Microscopes showed the development of bonding between the composite components. Compostes without coupling agent showed lower bonding strength between polypropylene and fiber as indicated by fiber pull out. However, in the composites containing coupling agent, the fiber fracture was observed.

Current study was done with the aim of investigating the effect of polymeric multilayers of cationic starch and anionic starch upon CMP fibers using layer-by-layer technique on its pulp and paper properties. Consecutive cationic and anionic starches layering experiments (respectively 1% and 0.5% dose of each starch based on oven-dry fibers) with layering time of about 10 minutes were conducted to assemble one to five successive ionic starches onto CMP fibers. Pulp properties including: freeness, water retention value and zeta potential were examined. Then, handsheets with basis weight of about 60 g/m2 were prepared and their properties were analyzed. Succeeding variation of zeta potential designated formation of successive layers of starches onto the CMP fibers. Furthermore, pulp freeness and water retention value has been enlarged by increasing the number of formed layers. The results of paper properties analysis showed that bonding-ability of fibers including tensile index and burst index have been considerably improved. The prepared SEM micrographs indicated of making more bonds between fibers due to the higher absorption of cationic starch.

In this study was to evaluate the impact of the truss structure on stiffness and stress distribution in the truss structural members. Made and synchronizes this structures with any Populus_ Nigra lumbers, in finally made 44 truss structure with 11 varying samples and 4 replicates. were used by two joint like friction joints was created with Glue stick and dual joint was created with nails to the 4.5 cm and calculate the resistance trusses structures by mechanical testing machine with 12.5 mm/min loading speed and 3.5 KN than mechanical test results showed, Hip Girder truss most resistance stress distribution and were the least impact on the strength and distribution of tension truss structure is significant in 95%. To show the stress distribution on the members, modeling software was AutoCAD, Catia and finite element analysis software was ANSYS. In finally the results show that maximum stress concentration, failure to engage in experimental mode.

Wet tensile strength is very important in some cellulosic health products. When these products produced during the recycling process some of the characteristics in pulp suspension due to lack of stability of desirable quality properties is difficult to achieve. In this study, using a variety of different doses of cationic polymers with laboratory methods, at first reduced the anionic charge amount in pulp suspension gradually. Then the Poly (amine) amide epichlorohydrin and its stabilizer injected to the suspension. The pulp suspension and physical properties of handsheets were evaluated. The type and amount of cationic polymers have a significant effect on the reduction of anionic charge of pulp suspension and the resulting increase in wet tensile strength and other physical resistance of handsheets. The effect of polymers resulted that anionic charge of suspension improved from 237 µeq /L in control samples to32µeq/L in the best conditions. Physical properties of handsheets improved after chemical treatments with different amounts of variety of polymers. Wet tensile strength increased than13 N/m to 121N/m, dry tensile strength improved 2730 N/m to 2860 N/m the burst resistance increased than 146 KPa to 160KPa in superior treatment using 135 mg/L of Gfloc F10. Stepwise regression analysis showed the significant relationship of the anionic charge in the pulp suspension and the physical properties of handsheets. So using different cationic polymers can be reduced the anionic charge of the pulp suspension and improved the quality properties of paper base products.

In this study, the effect of beating time on morphologic, physical and strength properties of soda and monoethanolamine pulps obtained from wheat straw was studied, in order to optimize the time for beating operation. Beating of the pulps was applied in different time by laboratory jokromill beater. The results showed that rising time of beating leads to increasing the freeness (SR) of pulps and monoethanolamine pulp reached to maximum amount of freeness (SR) in less time as compared to soda pulp. In addition, it is found that monoethanolamin pulp obtained the maximum amount of tensile index (91.3 N.m/g) after 30 min beating time and after that longer time of beating process had no significant effect on increasing the tensile index. About soda pulp it is observed that tensile index was increased significantly by rising the time of beating process and for this kind of pulp, maximum amount of tensile index (87.7N.m/g) was obtained in 50 min beating process. The highest burst index for soda pulp was 5 Kp.m2 which was obtained by 50 min beating process. About mono ethanolamine pulp burst index increased by rising time of beating Process and reached to its maximum amount (5.6 Kp.m2) and after that its amount decreased. Rising the time of beating process led to decreasing the tear index in both of kinds of pulp consist of monoethanolamin and soda pulp. The results showed that mono ethanolamine pulp had the higher yield and better beating ability in comparison with soda pulp which can be caused by better ability for carbohydrates and minerals retaining in monoethanolamin pulp.

In this research, resistance and stress concentration on the seat structure were examined by changing the type of connection (tongue and groove connection , and double connection). platanus orientalis used to make wooden chairs. Moreover, we applied Ansys to calculate resistance and mechanical testing machine with a load of chairs 7/12 mm per minute to show the stress distribution on the chairs members . The results show that chairs by tongue and groove connection and having a simple structure and with bail , have more resistance and less stress distribution than a double chair with a simple structure and with indicating connection and the impact of the type of connection were significant on the chair resistance . The stress distribution shows that the maximum stress concentrations on the horizontal joints are visible . Finite element models show that the stress distribution is more uniform in chairs with tongue and groove connections.

As a result of water treatment and during the water softening and hardness reducing process, calcium carbonate deposits with other impurities produced, collected and buried as mineral sludge. This study was done to investigate the effect of using calcium carbonate filler (as a byproduct of water treatment process in Mazandaran wood and paper mill) on strength properties of fluting paper produced from both old corrugated container (OCC) and neutral sulfite semi chemical(NSSC) pulps. Calcium carbonate added to the pulps at levels of 5, 10 and 15 percentage of bone dry weight of paper. The air resistant with the tensile index, burst index, tear index and resistant to fluting of handsheets were measured and compared to control handsheets (samples without calcium carbonate). The results showed that the use of calcium carbonate from the water treatment has a negative impact on fluting paper strength properties. Calcium carbonate filler negative impacts on virgin pulp (NSSC) and recycled pulp (OCC) is different and is more in OCC pulp.

Paper relics have historical, artistic and scientific values in the human cultural heritage viewpoint. Given the importance of this material, its preservation is a matter of great interest. Biodeterioration and specially fungi are one of main decay factors of cellulose structure of paper. The aim of this study was to determine the minimum inhibitory concentration (MIC) of Benomyl for Aspergillus niger, Aspergillus Terreus, Penicillium and Cladosporium isolated from infected papers and manuscripts. Isolates were tested for sensitivity to benomyl also been compared with each other. Fungal genera were identified based on macroscopic and microscopic characteristics of isolated samples by using slide culture method and optical microscope disk diffusion method was used In order to determine the minimum inhibitory concentration of Benomyl alcohol treatments on paper. ASTM D 2020-92 Standard Test Methods for Mildew were used to assess fungal resistance of treated paper. These test methods cover the qualitative determination of mildew (fungus) resistance of paper and paperboard, particularly those types which have been given a fungus resistant treatment. The results showed that all tested fungi are sensitive to Benomyl and Benomyl alcohol treatment prevents the growth of isolates on paper. Penicillium has the least MIC 12/5 ppm, and the highest MIC, 100 ppm, belong to Aspergillus niger. MIC obtained for Aspergillus terreus and Cladosporium was 50 ppm. In all isolates with increasing concentration of ethanolic solution of Benomyl the diameter of colonies in comparison with the control group, decreased And the percentage inhibitionof fungal growth on paper increased the results demonstrarte that the 100 ppm concentration of Benomyl in ethanol can be the lowest concentration necessary to provide an efficient antifungal action.

The aim of this study was evaluation the mechanical properties of medium density fiber board of domestic production of Iran Company and imported medium density fiber board (Malaysia). Due to lack of knowledge and lack of access_to information, factors and variables influencing in production of fiberboard papers in industry especially imported boards, to better understand the differences of infrared radiation to reveal a vertical density profile of boards and infrared Spectroscopy (FT_IR), to identify compounds of fibers and the links caused by adhesive and dimensional analysis of fibers of the boards were used. The results of statistical analysis showed that the boards of domestic production_than to the imported boards have high mechanical strength. So that average flexural strength and modulus of elasticity in order for boards constructed in the country 34.56 and 2762 MPa and 2277 MPa, and it is 24.87 for imported supplies. The average internal bond strength of boards manufactured domestically MPa 0.78 and 0.58 have been of imported for the board. The results of density profile showed that the boards made into the country, in middle layer have 599 up to 615 kg/ m3 density and also surface layers have 1060 kg/m3, while the imported boards in middle layer have 533 up to 571 kg/m3 density and also surface layers have 1020 kg/m3 density. According to the results obtained from FT_IR spectra’s of the samples. Domestic boards than to the imported boards have more hydrogen links. Beside, pictures of analysis of fibers showed that the highest, lowest and average of fibers length for the domestic boards 260, 10 and 120 and lowest and average of fibers length for the imported boards 190, 5 and 45 were obtained, respectively.