Iranian Journal of Wood and Paper Science Research
Year:2017 | Volume:32 | Issue:1|Papers Count:15

The present research work has investigated the physical and mechanical properties of hygrothermally modified poplar (Populus deltoides L.) wood. The poplar wood blocks were treated hygrothermally at temperatures of 130, 150 and 170oC and for 20, 40 minutes treatment 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. The hygro-thermal treatment significantly improved the dimensional stability of the samples. It was also found that the hygro-thermal treatment increased collapse, surface roughness and modulus of elasticity due to the treatment. However, wood mass, specific gravity and bending strength of the treated poplar wood decreased. It was revealed that the mass loss, density reduction as well as collapse in wood are correlated with treatment temperature as well as the treatment time. While, higher treatment temperature treatment time increases the dimensional stability.

In this study, 10 samples of beech wood, without apparent defects, and the dimensions of 360´16´16 cm (length´radial´tangential) were selected, and exposed to variable temperatures (60, 80, 100, 120, 140, 160, and 180oC) and moisture (moisture content at: saturated with water (EMC=65±5%), equilibrium moisture content exposed to air (EMC=19±5%), and conditioning moisture content in controlled climatic chamber (EMC=12±2%). All samples after reaching the equilibrium, were tested under free flexural vibration in two longitudinal-tangential and longitudinal-radial planes, and some of the physical, mechanical, and acoustical properties in both planes were measured. The results showed that the correlation coefficient of the first three modes of flexural vibration in both planes of samples treated under climatic chamber had a similar behavior, but when the samples were treated in the water-saturated condition, they showed an adverse behavior in each plane. The effect of increasing the temperature above 100oC initiated stresses resulting from shrinkage leading to the development of micro-cracks in cell walls and reduction in the modulus of elasticity and ultimately reduction in wave propagation ability of wood. Thus, in the damping vibration values in both longitudinal-tangential and longitudinal-radial planes of the samples were increased. The concurrent changes in modulus of elasticity and damping vibration in both vibration planes are a desirable indicator for monitoring the process from the primary logging process stages to processes such as wood drying and heat treatment.

The delignification reaction in pulping process ofP. deltoides wood was investigated to obtain the relation between residual lignin in the pulp and cooking time. The samples were 10 years old Populus deltoids wood which were collected from Chamestan Research Station located in Noor Mazandaran province. Kraft pulping with the pulping conditions; 25% sulfidity, 14% alkali, 5: 1liquor to wood ratio, maximum cooking temperature as 155, 165, 175 degree centigrade. Kappa number and the yield of pulps were measured and residual lignin was calculated for each sample. Using the models predicted for rate equation and trial and error method in excel 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 deltoids wood in temperatures of 155oC, 165oC and 175oC 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 content in the pulp.

In this research the effect of chemical modification with Polycrease ECR on the functional performance of poplar wood to be used as wood/polymer were investigated. Polycrease ECR the modified dimethyloldihydroxy-ethyleneurea (DMDHEU) was used for chemical modification of wood by impregnation method. Specimens were prepared according to the ASTM standard test methods and treated applying two levels of 30 and 50%. Modification process of specimens were performed for 24 hours in temperature of 120oC. 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. The results of modified specimens were compared with untreated control samples. 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 the 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, the influence of chemical modification on the physical properties (long term water absorption and volumetric swelling) were dominant.

The influence of Multi Walled Carbon Nano Tubes (Non-functionalized and functionalized) on mechanical properties of polypropylene-old corrugated container (OCC) fibers composite is investigated. The composites samples were prepared using 20% OCC fibers, 80% polypropylene and without or 3% MAPP. Acidic oxidation method was used to functionalize the MWCNTs. Three levels of either treated or non- treated multi walled carbon nano tubes (0%- 0.5% - 1%) were added. 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 statistiaclly significant. The bending strength and elasticity as well as the izod impact strength were increased as the higher amount of nanotubes was added to the composite. Scanning Electron Micrographs showed the development of bonding between the composite components.Composites 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 dominant.

The aim of the present study was to investigate the effect of precipitation of polymeric multilayers of cationic and anionic starch on CMP fibers using layer-by-layer technique on its pulp and paper properties. Consecutive cationic and anionic starch layering experiments (respectively 1% and 0.5% dose of each starch based on oven-dry fibers) with precipitation time of about 10 minutes were conducted to assemble one to five successive ionic starch layers on CMP fibers. Pulp properties including: freeness, water retention value and zeta potential were examined. Then, hand sheets with basis weight of about 60 g/m2 were prepared and their properties were measured and analyzed. Succeeding variation of zeta potential designated formation of successive layers of starch on the CMP fibers. Furthermore, pulp freeness and water retention value has been improved 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 SEM micrographs indicated the formation of more bonds between fibers due to the higher absorption of cationic starch.

In this study, the effect of truss structure on the stiffness and stress distribution in the truss members was investigated. Finite element method (FEM) and two ANSYS and Autodesk software were used to show of stress distribution on the members. Samples with eleven different structures in four replications were made from poplar (Populus nigra L.) wood. Two dowel joints and friction joints were used in the truss fabrication. To calculate of the resistance of the trusses, first the trusses were loaded at the rate of 12.5 mm min-1 by mechanical testing machine. The results showed that the Hip Girder truss have highest resistance and lowest stress distribution compared with other trusses. The effect of truss structure on the resistance and stress distribution was statistically significant in 95% confidence level. The results showed that the maximum stress concentration appeared identically with experimental failure mode.

Wet tensile strength is very important in some cellulosic hygienic products. In the production process of these products using recycling process some characteristics of pulp suspension due to lack of stability of desirable quality properties is difficult to achieve. In this study, a variety of different doses of cationic polymers were used at laboratory scale. First the anionic charge of the pulp suspension was gradually reduced. Then the Poly (amine) amide epichlorohydrin and its stabilizer injected to the suspension. The pulp suspension and physical properties of hand sheets were evaluated. The type and amount of cationic polymers showed a significant effect on the reduction of anionic charge of pulp suspension and the resulting increase in wet tensile strength and other physical properties of hand sheets. The addition of polymers resulted that anionic charge of suspension improved from 237 meq /L in control samples to32meq/L in the best conditions. Physical properties of hand sheets improved after chemical treatments with different amounts of polymers. Wet tensile strength increased from13 N/m to 121N/m, dry tensile strength improved 2730 N/m to 2860 N/m the burst strength increased from 146 KPa to 160KPa best 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 handsets. So using different cationic polymers can reduced the anionic charge of the pulp suspension and improves the properties of paper 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 Jokro mill beater. The results showed that rising time of beating leads to increase the freeness (SR) of pulps and monoethanolamine pulp reached to maximum freeness (SR) in lesser time as compared to soda pulp. In addition, it is found that monoethanolamin pulp reached the maximum tensile index (91.3 N.m/g) after 30 minute beating time and longer time of beating process had no significant effect on increasing the tensile index. Soda pulp tensile index was increased significantly at longer time of beating process and for this kind of pulp, maximum value of tensile index (87.7N.m/g) was reached in 50 minute beating. The highest burst index for soda pulp was 5 kPa.m2/g which was reached after 50 minute beating process. The burst strength index of mono ethanolamine pulp increased by rising time of beating process and reached to its maximum value of 5.6 kPa.m2/g and at prolonged time after it was decreased. Rising the time of beating process led to decreasing the tear strength index of both pulps identically. The results showed that mono ethanolamine pulp had the higher yield and better beating ability in comparison with soda pulp which can be due to hgiher 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 dowel joint). Sycamore (Platanus orientalis) wood used to fabricate wooden chairs. Mechanical testing machine to load the chairs at the rate of 7.12 mm per minute. Ansys was used to calculate the stress distribution on the chairs members. The results showed that chairs fabricated 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 indicating connection. The impact of the type of connection were significant on the chair resistance. The stress distribution dicateds that the maximum stress concentrations on the horizontal joints are visible. Finite element models showed that the stress distribution is more uniform in chairs with tongue and groove connections.

Water treatment and water softening process generates, calcium carbonate precipitates containing other impurities. These calcium carbonates is collected and buried as mineral sludge. This sludge is available as a byproduct of water treatment process in Mazandaran wood and paper mill. This study was done to investigate the effect of using this calcium carbonate as filler on strength properties of fluting paper produced from both old corrugated container (OCC) and neutral sulfite semi chemical (NSSC) pulps. Calcium carbonate was added to the pulps at levels of 5, 10 and 15% of bone dry weight of paper. The air resistant 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 severe 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. Bio-orgaisms and specially fungi are one of main decaying 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 and also have 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. In order to determine the minimum inhibitory concentration of Benomyl alcohol treatments on paper followed by disk diffusion method. 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 and such 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 exposed to increasing concentration of ethanolic solution of Benomyl the diameter of colonies in comparison with the control group, decreased and the percentage inhibition of fungal growth on paper increased. The results demonstrated that the 100 ppm concentration of Benomyl in ethanol can be the lowest concentration necessary to provide efficient antifungal action.

The aim of this study was to evaluate the mechanical properties of domestic and imported medium density fiber board. X radiation techniques were used to reveal a vertical density profile of boards and X Spectroscopy (FT_IR), was employed to identify the compounds present in fibers and the adhesive bonds and dimensional analysis of fibers. The results of statistical analysis showed that the mechanical strength domestic boards are higher than to the imported boards. Average flexural strength and modulus of elasticity domestic boards were measured as 34.56 and 2762 MPa and 2277 MPa, respectively and the relative values for imported boards were 24.87 and 2277 MPa. The average internal bond strength of domestic and imported boards was determined as 0.78 and 0.58 MPa. respectively. The results of density profile measurement showed that the density of the middle layer of domestic boards varies between 599 up to 615 kg/ m3 and surface layers as 1060 kg/m3, while the density of the middle layer of imported boards varies between 533 up to 571 kg/m3 and surface layers as 1020 kg/m3 density. According to the results of FT IR spectra. Domestic boards show more hydrogen bonds compared to imported board. Dimensional analysis of fibers showed that the highest, lowest and average of fibers length for the domestic boards is 260, 10 and 120 mm. and highest, lowest and average of fibers length for the imported boards 190, 5 and 45 mm. respectively.