IRANIAN JOURNAL OF WOOD AND PAPER INDUSTRIES
Year:2011 | Volume:2 | Issue:1|Papers Count:10

Enzymes are protein molecules with complex structures that accelerate the biochemical reactions.Activity of these chemical compounds is accomplished at limited range of pH, temperature and concentration. In this study, the effects of different concentrations of cellulose enzyme were investigated on deinking of old newsprint. Old newsprint (ONP) was repulsed at 5% consistency for 10 minutes in disintegrator with total revolution number of 26500. Enzymatic treatments of recycled ONP pulp were done under constant conditions (10% consistency, treatment time of 15 minutes, pH range of 5-5.5) at different cellulose concentrations of 0.025, 0.05, 0.1 and 0.2% (based on oven-dry waste paper). The optical and physical properties of the standard paper (60g/m2) made at different concentrations of cellulose were evaluated in comparison with control pulp (untreated ONP pulp with cellulose). Overall, the results achieved by comparison the optical properties of the paper produced indicated that using cellulose in deinking of ONP led to increase the brightness and the yellowness and decrease the opacity. The brightness was improved to a maximum level of 47.5 ISO %, but the yellowness was decreased to a minimum level of 11.3 ISO %, while the brightness reduced and the yellowness increased at higher concentrations than 0.05% cellulose. The highest opacity of 99.3 ISO % was achieved using 0.1% cellulose even higher than control pulp. The results gained by comparison the physical properties of the paper showed that using cellulose resulted in decrease of paper caliper, air resistance and density and improve the freeness of pulp.

In this research, the effect of nano-zycosil, nano-zycofil, acid catalyzed lacquer and nitrocellulose lacquer and polyester on improving the water absorption and contact angle of wood was investigated. Some boards were prepared from the sapwood of poplar (P.nigra). They were dried based on T6E3 schedule and some specimens were cut according to EN 927-5 standard (20 × 70 × 150 mm). They were coated and immersed with the nano particles and clear paints. The clear paint- and nanoparticles-coated samples were dried in laboratory environment and in an oven at the temperatures of 103 2oc, respectively. After drying process, the water absorption of the samples was measured after 2, 24, 72, 168 h immersion. The contact angle of samples was measured after 1 and 10 seconds. The results revealed that the pattern of water absorption for the paints and nanoparticles is different. The samples coated with combined acid catalyzed lacquers and nitrocellulose lacquers and those coated with nanozycosil had the highest resistance to water absorption. The greatest contact angle was observed for the samples coated by nanozycosil.

Heat treatment of wood is an effective method to improve the dimensional stability and durability against biodegradation. Heat treatments of beech wood in 2 different mediums (hot water and steam) at 180ºC were compared by physical, mechanical and anatomical properties. Mass loss in hydrothermally treated wood was higher than hydrothermally treated specimens. Mechanical properties (MOR and MOE) were decreased in both mediums, but strength loss was higher for hydrothermal treated samples. Anatomical changes were investigated by means of a light microscopic analysis. Beech was sensitive to collapse of the vessels in both mediums. In treated beech, radial cracks were observed near the rays both in hydro and hydrothermal treatments.Depletion of extractives on the cell walls and deformation of libriform fibers near the vessels were also observed.

In this research, drying kinetics and mass transfer coefficients (permeability and diffusion) of hornbeam wood (Carpinus betulus) from Nooshahar region were investigated. For this purpose, several boards with two nominal thicknesses of 2.5 an 5 cm were prepared from a freshly cut log.The boards were dried inside a laboratory kiln at the dry bulb temperature of 40°C and relative humidity of 50% to the final moisture content of 6%. The pattern of moisture loss, thermal diffusion, final moisture gradient along the board thickness, transverse permeability and diffusion coefficients were then measured. The results showed that by increasing of board thickness, the rate of moisture loss decreased, particularly in the hygroscopic range and the moisture gradient increased, but the thermal diffusion was not affected. The transverse permeability and diffusion coefficient of hornbeam wood was 2.91×10-19 m2 and 3.29×10-9 m2s-1, respectively. Overall, it can be concluded that due to low transverse permeability coefficient of hornbeam wood, this species is difficult to be impregnated in common wood preservation process. In contrast, due to low diffusion coefficient, hornbeam wood is recommended for applications where high resistant to water vapor diffusion is required.

The influence of chemical treatment time and temperature on production of chemi-mechanical pulp from Colza stem is studied. Three treatment times (15, 30 and 45 minutes) and two treatment temperatures (125 and 145 oC) were investigated. Chemical charge as 4% NaOH and 8% Na2SO3 as was kept constant. Accepted pulp yield varied between 53.8% and 63% and the total yield was measured between 57.6% and 68.9%. The residual lignin in lower yield pulp was 19% and higher yield pulp was 20.4%. Holocellulose content of pulps varied between 72.5%- 74% and freeness was between 520-590 ml CSF. Fiber classification using Bauer-McNett procedure showed that the average fiber length of unrefined pulp is between 0.6-0.7 mm, and the fine content (P100) is between 9% and 10.4%, Pulp freeness was reduced from original value of 520 to 590 ml CSF to about 300 ml CSF as pulps were refined in PFI mill applying 500 revolutions. The unrefined pulp strength including tensile index, burst index and tear index were measured as 15.48- 26.13 N.m/g, lower than 1 kPa.m2/g and 2.91- 4.34 mNm2/g respectively. All the indices after refining in PFI mill using 500 revolution were increased to 19.74-35.19 N.m/g, Max.1.70 kPa.m2/g and 3.21- 4.68 mNm2/g respectively.

In this research, the effects of chemical foaming agent and wood flour content on cell morphology, density and mechanical properties of HDPE/EVA/ Wood Flour hybrid foamed composites were investigated. For this aim, composites were prepared via melt mixing in an internal mixer, then foamed using single-stage batch foaming method. Then mechanical properties such as flexural strength, flexural and tensile modulus and density were measured. Morphology of the samples was also evaluated by scanning electron microscopy (SEM). The results of this study have indicated that the flexural strength, flexural and tensile modulus and density increases with the increase of wood flour content. However, with addition of chemical foaming agent content and EVA content, mechanical properties and density of foamed composites decreased. Moreover, wood fiber acted as nucleating agents that substantially reduced cell size and increased cell density. In addition, EVA plays an important role in foaming process by increasing the melt viscosity of the polymer matrix, in a way that samples with higher content of EVA have the highest cell density and the lowest cell size.

In recent years, the plywood and veneer industry of Iran has undergone negative growth due to shortage of proper diameter logs and also lack of innovative technologies for the use of low diameter logs; Moreover, demands for lignocelluloses products has been growing as a consequence of significant increase in population and expansion of construction Industry, especially in major cities. Hence, it is necessary to cultivate fast-growing species. For this purpose four logs of paulownia (120 cm length and 55 cm diameter) were prepared from the Gorgan shast Kalate forests and then transported to Kosar factory in order to prepare veneers. Produced layers were transferred to the wood laboratory of Gorgan University. Then plywood was manufactured from paulownia species on the basis of the standard 3210 of ISIRI (Institute of Standards and Industrial Researches of Iran) and common tests of plywood were made. The results showed that the mechanical properties of manufactured boards were upper than with standards defined by ISIRI and the physical properties of those manufactured with urea formaldehyde glue were lower than standards which can be considered as negative properties; Albeit, they were not significant and can be disregarded.

In order to determine the fiber dimensions, physical and chemical properties of the bast and without bast stalk of Sahel-Variety of cotton stalk, required samples were prepared and studied. The results showed that fiber and lumen diameter and cell wall thickness of without bast stalk fibers were greater than those of bast fibers, while bast fibers were longer. Thus, this fiber can be classified as short and medium length fibers respectively. Data showed that the Length/ Diameter ratio and Runkle ratio of the bast fibers were greater than those of without bast stalk fibers, and flexibility coefficient in without bast stalk fibers was greater. Stalk with higher diameter had less bast proportion. Oven-dried density and swelling and shrinkage values of thicker stalks were greater than those of thinner ones, but apparent and basic densities, as well as porosity in thinner stalks were higher. Chemical Properties of bast and without bast stalk were respectively as follow: cellulose 39.27% and 48.3%, lignin 23.93% and 21.89%, extractives 6.06% and 3.23%, ash content 6.36% and 1.85%, one percent sodium hydroxide solubility 48.35% and 21.275% and hot water solubility 19.48% and 9.68%.These indicate that without bast stalk fibers are more suitable than bast fibers for pulp production, but bast fibers are preferred in terms of fiber length.

In order to investigation the effect of increasing board density and amount of UF resin on particleboard properties, this study was carried out. Regarding two variable parameters: board density at three level (520, 620 and 720 Kg/m3) and percentage of UF resin (6, 7, and 8%), one layer particleboards with16mm nominal thickness were manufactured. Physical and mechanical properties such as MOR, MOE, IB and thickness swelling (after 24 hours immersion in water) were measured. The results showed that with increase in board density from 520 to 720 Kg/m3, MOR and MOE were increased and dimensional stability was improved. But increase in board density had no significant effect on IB. The results of contour plots showed that manufacturing boards with density of 600-650 Kg/m3 and 6% UF resin, all of mechanical properties were maintained in standard specified limits related to those boards and using adequate amount of water resistant materials will Cause improving of thickness swelling after 24 h immertion.

Considering the value and importance of wheat flour in our country, replacement of a new type of filler instead of wheat flour in glue combination in plywood industry is necessary. In this study the possibility of using wood flour of poplar and OCC (old corrugated container) fiber as filler in the combination of urea formaldehyde glue has been studied. The plywood was manufactured from Poplar species (in core of plywood) and Hornbeam veneer (in back and face of plywood) on the basis of the standard 3210 of ISIRI (Institute of Standards and Industrial Researches of Iran) and the physical and mechanical properties of experimental plywood were measured. The results of statistical analysis of variance and Least Significant Difference (LSD) showed that Mechanical and physical properties of samples made with fine OCC were more than that of control samples (the Samples made with wheat flour filler). The results also showed physical and mechanical properties of plywood increase by adding 10 to 15 percent of OCC to adhesive.