Iranian Journal of Wood and Paper Science Research
Year:2018 | Volume:32 | Issue:4 (61) |Papers Count:16

In this study, the potential of cotton stalks residues for the production of particleboard was investigated. Three resin dosage gradients of 0, 2 and 4% between surface and core layers (10% core: 10% surface; 9% core: 11% surface and 8% core: 12% surface) and three press times (3, 4 and 5 minutes) were selected as the variables and laboratory boards were fabricated. Then, the mechanical and physical properties of the boards were measured and statistically analyzed. The results of modulus of rupture (MOR), modulus of elasticity (MOE) and internal bonding (IB) measurements showed that as the resin dosage gradient increases, these properties increased and the effect of this variable on these properties was statistically significant. The highest values were reached when either 2 or 4% resin dosage gradients were applied. The effect of resin dosage gradient on thickness swelling after 2 and 24 hour immersion in water was also statistically significant and these properties were improved. The effect of press time on thickness swelling was also statistically significant and the lowest thickness swelling was observed at 5 minute press time. The results indicated that if either 2 or 4% resin dosage gradients between surface and core layers and either 4 or 5 minute press time is applied for the manufacturing of particleboards using cotton stalks residues, the specification of the boards meet the EN specification.

The objective of this research was to investigate the effects of total chlorine free (TCF) and elemental chlorine free (ECF) bleaching on optical and mechanical properties of bleached bagasse soda pulp. For this purpose, some unbleached bagasse soda pulp was randomly selected from Pars Paper industry. Then pulp was bleached with one, two or three stage sequences applying P, OP, OPY, O(Ep)P, EHP and O(Ep)H bleaching stages denoting oxygen(O), hydrogen peroxide(P), alkali extraction with hydrogen peroxide(Ep), sodium hypochlorite(H) and sodium dithionite(Y). The hand sheets with 70 gr/m2 were prepared from the above-mentioned bleached pulps, and then the optical and mechanical properties were measured using TAPPI standard test methods and compared. The results showed that brightness, greenness, tear (except EHP stages), tensile, burst, breaking length strengths and folds were increased and opacity and a* factor were decreased by ECF and TCF bleaching sequences. The effects of TCF bleaching sequence were more sensible than ECF bleaching sequence in improving bagasse soda pulp properties. In general, role of three stage OPY and O(Ep)H and two stage OP bleaching were better than EH(control) and unbleached bagasse soda pulps mill in improving brightness and paper strengths.

In order to establish a kiln drying schedule for Iranian Beech (Fagus orientalis) Wood, commercially cut lumbers with the thickness of 5. 5 cm, were selected from Shast-Kola region, Gorgan. Then, lumber were dried under the kiln schedule based on diffusion theory (from Malmquist's relations) to the final moisture content of 12± 2%. This schedule was adopted and implemented for three kiln loads with three different initial moisture contents, 66. 6, 58 and 45 percent. Initial drying bulb temperature (first step) and wet-bulb temperature were calculated, respectively, at 46 ° C and 45 ° C for all three schedules. The severity of surface checks, end checks and warp (bowing, crooking, twisting) in the lumbers were measured before and after the drying process. Quality control methods were employed to analyze the wood defects. Results showed that kiln drying of beech wood based on diffusion theory was satisfactory and the severity of changes in defect were statistically acceptable in all loads. Superior characteristics of this method, was related to nearly zero surface checks in samples, because the moisture content was reduced slowly.

In this study, the effects of using filtrated black liquor from bagasse soda pulping (BLBSP) for surface coating of recycled paper was studied. Filtrated black liquor with different concentration (30, 37, 44) at the rate of 2. 5 gr. /m2 /side (5 gr. /m2 /side in two passes in case of 44% concentration) was applied on recycled based paper and the properties of the product were determined. The BLBSP filtration improved the paper properties compared to unfiltered, due to separation of impurity and coarse material. Higher concentration and content (in case of 44% concentration) of the applied coatings increased the paper basis weight (up to 44%) and reduced water absorption (to <30%), because of the hydrophobic nature of material in liquor (lignin and minerals). But the optimum treatment with respect to the tensile, burst and tear strength was related to the lowest applied concentration, which are attributed to the easier BLBSP penetration into the paper structure and contribution in fiber bonding. Compression and bending strengths that were increased by the liquor concentration (bending stiffness up to >200% and compressive crush resistance up to >150%). In this regard, film formation, thickening the paper and also the effective role of lignin could be noted in addition to bonding enhancement. Repeated application (in case of 44% concentration) of the BLBSP did not impart any significant improvement of the all properties, and decreased these properties.

The aim of this study was to investigate the effects of natural weathering induced by critical climate conditions in Khuzestan on quality of sugarcane bagasse pulp in Pars Papermaking Company. The experimental samples were selected from fresh and also stored bagasse for durations of 6 months, 1, 2 and 5 years. The mechanical and the chemical properties as well the color variations of the paper samples were measured. The results showed that the long storage durations significantly decreased the quality of raw materials as observed in hand sheet tensile and fold strengths. The results illustrated that the amount of lignin and extractives increased (44% lignin and 32% in extractives, respectively) and also the amount of cellulose and hemicellulose decreased (10% for cellulose and 43% for hemicellulose) after 5 years storage in the yard. According to the results, there was an obvious difference in L and a color index of pulps produced from 5 years old bagasse compared to those of fresh bagasse. Finally, the use of discolored and weathered bagasse could cause the loss in the final product quality which means more chemical treatment for bleaching and longer fiber to be used in paper making process.

In this study, the liquorice roots (Glycyrrhiza glabra) which were extracted in the Liquorice factory of Kerman, was used as raw material. The residues, after pre-hydrolysis with 2% sulfuric acid at 130° C in 60 minutes was cooked at temperature of 170° C, chemicals charge of 20% NaOH, and four cooking times of 15, 30, 60 and 90 minutes and liquor to fiber ratio of 7: 1. Soda pulps yield, lignin percentage, water retention value (WRV), viscosity and crystallinity were measured. Results showed that at longer cooking time, pulp yield and lignin percentage are decreased and WRV increased. Also, pulp viscosity after 30, 45 minutes cooking was increased by increasing in cooking time which is probably the consequence of false viscosity. In addition, based on characterization of pulp samples by XRD, progressive cooking times from 15 to 45 minutes, decreased the sample crystallinity and at 60 minutes time, its value was increased. Correlating the pulp viscosity with trend of lignin removal on progressive cooking time, it can be due to precipitation of hemicellulose like xylan on the crystalline region of cellulose chain. Therefore, according to the results and based on bio-refinery concept, cooking time of 30 minutes can be suggested as the option time for production of high value-added products in scarification process.

Utilization of paper as packaging material and developing technologies such as sensors on paper-based substrate are drastically dependent to control of cellulosic fiber hydrophilicity and enhancement of its hydrophobic properties. Thus, this work carried out with the aim of developing hydrophobic surface on cellulosic fiber applying layer by layer (LBL) method while keeping and enhancing the properties of paper network. The deposition was implemented by titanium dioxide nanoparticles and polyacrylic acid as cationic and anionic layer respectively on the fibers of unbleached hardwood kraft pulp and using Zycosil and fluoroalkyl silane on the last layer. The hand-sheets were then made using this modified fiber. The contact angle and roughness were measured to evaluate the effect of layers on hydrophobicity. The results indicated that roughness increased with the number of layers. The instant contact angle was also increased with the number of layers and reached approximately to 110 degrees at 7th layer. The dynamic contact angles dropped with increasing the number of layers. The fluorosilane deposition as 8th layer in mixture with Zycosil showed more effective on surface energy reduction. The instant contact angle of Zycosil treated paper was measured as125 degrees which dropped significantly to 48 degrees after 30 seconds. However, fluorosilane modified paper exhibited contact angle of 140 degrees at the same time. In addition, the presence of titanium dioxide nanoparticles on the surface of fiber was demonstrated by scanning electron microscopy (SEM) of paper surface.

This study was carried out to investigate the effect of bagasse storage time and moisture content on the physical and mechanical properties of particleboard. For this purpose, wet depitted bagasse was used and samples were stored in bales. Four storage times (1. 5, 3, 4. 5 and 6 months) and two moisture content (45% and 55%) were investigated and after predetermine times, particleboards were made. Bagasse chemical properties (pH, acid and alkaline buffering capacity) were also determined. The mechanical and physical properties of the boards were measured and statistically analyzed using factorial experiment and complete randomized design. Then, Duncan multiple range test was used for grouping of the averages. The results revealed that at lower bagasse moisture content, the sample pH and acid buffering capacity were decreased and increased, respectively. Boards bending properties and thickness swelling after 24 hours immersion in water were improved. At longer storage time, the bagasse tends to be alkaline, and the minimum of board internal bond strength was obtained after 1. 5 month storage time. The physical properties of boards were improved with increasing of storage time.

In this study, the properties of fibers recycled from MDF wastes as one of the important resources of raw materials for MDF production were investigated. Two different methods including ohmic heating (for 2 and 4 minutes) and hydrothermal method (at 105˚ C for 150 minutes) were utilized for recycling the MDF wastes and the virgin fibers were used as control sample. The chemical composition of fibers (lignin, cellulose and hemicellulose content), as effective variable on quality of fibers was measured. Also for probing the chemical characteristic of fiber surface, FT-IR test was utilized. In addition, the wettability of fibers was determined using water contact angels on fibers surface. The results showed that recycling process changed the chemical composition of fibers. Most of the changes were occurred in hemicellulose and extractives content. The results of FT-IR test revealed the existence of more carbonyl groups and furfural and lower amount of hydroxyl groups in recycled fibers compared to virgin fibers due to esterification process. The wettability of fibers was decreased after recycling process especially in hydrothermal method.

Mazandaran wood and paper industry is an integrated and the largest manufacturer of paper in the Middle East. Chemical and energy recovery of black liquor is one important aspect of wood pulping which has been intensively studies. Liquor concentration is the most important step in chemical and heat recovery which is used in Mazandaran wood and paper industry. In this work, liquor concentrator unit was simulated by Hysys software. Then, simulation results were compared with factory data and acceptable results were obtained. In the next step, the effect of operating conditions of the two main feed streams was studied. The results showed that with increasing of weak liquor temperature, the concentration of outgoing liquor flow increases as per 40° C increasing of temperature, as much as 28% of the condensed value was increases. Also, by 10 kPa increase of the weak liquor pressure, approximately 39% of condensed value decreases. By increasing the pressure and flow rate of steam, concentration of outgoing liquor increases, while, increasing for flow rate was sharply increased followed by lower rate of increase. The effect of steam temperature on the concentration of outgoing liquor at different pressures must be checked individually.

In this research, the manufacture of particleboard using lignocellulosic residues including mixture of wheat straw, tobacco stalks and hardwood wood chips were studied. The variable factors included the mixture of wheat straw and tobacco stalks with industrial wood chips in four levels0/100, 20/80, 40/60 and 60/40 (In any combination, tobacco stalks and wheat straw were used equally) and the amount of urea formaldehyde resin was at two levels 12 and 14% of the dry weight of the chips. The results showed that by increasing the mixture of wheat straw and tobacco stalk up to 60 percent, the physical and mechanical properties of the boards decreased significantly. But increasing the amount of adhesive consumption up to 14 percent had a positive impact on the physical and mechanical properties of the boards and improved internal bonding, bending strength and modulus of elasticity and dimensional stability of the boards. It means that by increasing the content of this type of wastes up to 40 percent with increase dosage of UF adhesive up to 14%, can be produced the boards with the mechanical properties at standard level.

Due to shortage of harvestable forest wood in Iran, the potential of CMP pulp production from various species of salix (S. alba, S. fragilis and S. aegyptica), in comparison with Populus deltoides, was investigate. The cooking liquor of Mazandaran wood and paper Mill, consisting of 50: 50 ratios of sodium sulfite and sodium bisulfite, and hydrogen peroxide, were used for chemical treatment and bleaching of the pulps, respectively. The results showed that the paper pulps of Salix fragilis and Salix alba had higher bulk and lower opacity than other species, respectively. The highest and lowest tensile strength of papers were related to S. alba and S. fragilis species, and, the highest and lowest burst and tear strength of papers have belonged to Salix aegyptica and Populus deltoides species, respectively. The data have shown that Salix species have a good potential to be used as raw material to produce CMP pulp at the cooking yield of 85%. According to the results of this research, Salix alba and are in first and the second priority to produce CMP pulp, at the cooking yield of 85%, respectively.

Today, due to the highly sensitive bearing load, joints in furniture and wooden structures are one of the most important scientific topics for research. The most recent method proposed to build wooden joints in Europe and the United States is a eco-friendly method, without using any type of adhesive, called "wood welding". In the present study, the effect of dowel diameter and surface on the tensile strength of softwood joints was investigated using two methods: wood welding and glue bonding. Fir (Abies alba) wood and polyvinyl acetate glue (PVA) was used for adhesive bonding, and Hornbeam (Carpinus betulus) wood was used for connector dowels and other parameters were kept constant. The structure of the welded surfaces was analyzed using scanning electron microscopy (SEM). The results of the tensile strength test showed that dowel diameter and surface texture have a significant effect on the tensile strength of joints in both joint methods.