جستجوی مقالات مرتبط با کلیدواژه "کاغذ بازیافتی" در نشریات گروه "جنگلداری"

The application of chelating agents to increase the efficiency of hydrogen peroxide is important in various related processes. Synthetic chemicals such as ethylenediaminetetraacetic acid (EDTA) are commonly used in these processes. The feasibility of using natural and environmentally friendly products instead of synthetic materials is an important and interesting subject. In this study, the performance of hydrogen peroxide in the deinking process was considered and the use of chitosan as a natural chelating agent in the deinking process of waste newspapers was investigated. The results showed that hydrogen peroxide bleaching along with the deinking process had a positive impact on the optical properties and reduced the burst and tear indices with no effect on the tensile and fold strengths. Chitosan, similar to the EDTA chelating agent, improved brightness, whiteness, dirt removal, and metal ion absorption in comparison with the treatment without a chelating agent. EDTA performs better than chitosan in removing ink from the pulp. Furthermore, in comparison to the treatment without a chelating agent, both chelating agents improved tear and burst indices, but had no effect on the fold and tensile strengths. The current research can be a small but promising step in using natural materials, such as chitosan biopolymers, instead of synthetic chelating agents, such as EDTA.

Light weight, good thermal and sound insulation, easy installation, high strength and low price are characteristics of sandwich panels that have found numerous applications in industry and construction today. In this composite two thin faces enclose a thick core layer that resists shear forces, which can be made of wood or wooden products. In this work, the improvement of the sandwich panel strength was investigated through changes on the material and cross-sectional shape of the core layer made from waste paper with square hollow shape. For the fabrication of the samples, it was necessary to design and manufacture a metal mold to form raw materials with specific ratios and hollow shaped. Different quantities of crushed paper with specified dimensions and two types of common resin in wood composites industry were used to prepare the core layers. The square honeycomb cores were sandwiched between the face layers from medium density fiber board. The first results of this study showed that compressed waste paper in the form of a core layer was an acceptable function in the structure of a lightweight sandwich panel. The density of the paper core had a significant effect on the improvement of flexural strength, which increased with increasing density. In addition, the type of adhesive had a significant effect on the flexural strength of the sandwich panel. Phenol formaldehyde adhesive further improved flexural strength, compared with the urea formaldehyde.

Improving the processing and the recycled paper properties is one of permanent concern of papermaking. In this research, the effect of nanochitosan addition on the process and product quality made of writing and printing recycled fiber was investigated. Being nano size and so its capability in access to the space between pulp suspension components and also its probable ability to make electrostatic and hydrogen bonds are the characteristics of nanochitosan. For this purpose, the chitosan nanoparticles were prepared and their size and shape was confirmed with AFM and FE-SEM. Also, the change in FTIR spectrum after conversion of chitosan to nanochitosan was considered and omitting the –NH2 in chitosan and creation of –CONH groups in nanochitosan by polymerization between chitosan and meta acrylic acid were confirmed. In next step, nanochitosan in four levels (0, 0.5, 1, 1.5 and 2% based on oven dry pulp) was used. The results indicated that nanochitosan was successful in increasing the mechanical properties (tensile, burst and tear indices) and process properties (drainage and fines retention) comparing the control treatment (no additive). Moreover, the comparing of nanochitosan and chitosan performance in the same consumption level (1% based on oven dry pulp) showed similar effect on mechanical properties but chitosan had better performance in process properties. Also, both of this polyelectrolyte showed better results on mechanical properties comparing the cationic starch at the same consumption level (1% based on oven dry pulp).

Upgrading recycled fiber properties has been a constant concern in pulp and paper industry. In this respect many researches has been applied. The present paper has been considered the effect of Amylase enzyme in pulping stage of old corrugated container (OCC). Also، pre-soaking of OCC (first step of pre-soaking for 6 hours in 3% consistency in different pH(s) and second step of pre-soaking at 60˚C for 18 hours with constant pH) in acid، neutral and alkaline pH on physical and mechanical properties (air resistence، tensile index، burst index، tear index and fold) of recycled paper and its effect on Amylase performance was investigated. Soaking itself improved mechanical properties. Alkaline pH pre-soaking had the most efficient effect on the mechanical properties. The results indicated that α-Amylase treatment improved the mechanical properties (except tear index) in the non-soaked samples but Amylase treatment had no significant effect on the soaked samples in the experimented pH ranges. The results showed that independent effects of soaking and alkaline treatments had superior effect on mechanical properties compared to enzymatic treatment. Statistically، none of treatments had significant effects on air resistence.

This study has been conducted in order to investigate the effect of using ONP recycled fibers on the mechanical and optical properties of local mixed hardwoods kraft pulp at Iran Wood and Paper Industry (Chooka). ONP and virgin kraft pulp have been prepared from Chooka’s waste paper storage and pulping digester, respectively. ONP has been repulped in the common method as used by paper recycling industry. After determination of the initial freeness of each pulp, they have been separately refined to reach the appropriate freeness value required to produce kraft paper. The pulps, then, have been mixed at 90.10, 80.20, 70.30, 50.50 and 30.70 percentage rates of recycled fibers and virgin kraft pulp, respectively. According to the related standard test method, handsheets were made from each treatment and their mechanical and optical properties have been measured. The results were compared with those of control sample (100% virgin kraft) using ANOVA technique and classification of the means was done by Duncan test. Finally, to determine the best treatment, normalization equation was calculated. The results show that the values of tensile, tear, and burst indices, folding endurance and density of the combined papers have been increased compared with those of control sample, but the values of bulk, thickness, brightness and opacity of the combined samples have been decreased. The scores of the treatments indicate that 50 percent of recycled fibers can be used in the furnish to produce paper with suitable mechanical and optical properties.

In order to determine the mechanical and optical properties of kraft liner paper made of the mixture of recovered OCC/ONP fibers with mixed local hardwoods virgin kraft pulp, OCC/ONP papers have been repulped in the common method of the paper recycling industry. The initial freeness value of each pulp was measured and they were separately refined to reach the suitable freeness value required to make kraft liner paper. The pulps have been mixed at (85, 10, 5), (80, 10, 10), (75, 10, 15), (70, 10, 20), (70, 15, 15), (65, 15, 20), (50, 25, 25), (25, 50, 25) and (25, 25, 50) percentage rates of virgin kraft pulp, OCC and ONP papers, respectively. Handsheets were made, according to the related TAPPI standard test methods, from each mixture (treatment) and their mechanical and optical properties have been determined. The results were compared with those of control sample (100% virgin kraft pulp) using ANOVA technique. Normalization equation was calculated to determine the best treatment. The results have shown that with increasing the amount of OCC/ONP fibers in the mixture of pulps, tensile, tear and burst indices of the produced kraft liner paper decreased and brightness increased, in comparison to those of the control sample. According to the calculated normalization equation, the score of each treatment showed that 25/25 percent of OCC/ONP fibers (totally 50 percent) can be used in the mixture of local hardwood virgin kraft pulp to produce kraft liner paper with appropriate mechanical and optical properties.

This study was performed to investigate the effects of refining on the mechanical and optical properties of waste newspaper. Waste newspapers were prepared from Gorgan Ettelaat newspaper Agency and were cut to 5 centimeter pieces, and then were soaked with sufficient distillated water. After 1 day fibers were separated by disintegrator and freeness values for each pulp before and after refining were measured. Waste newspaper was refined by PFI mill at 1000, 2000, 3000, 6000, 9000 revolutions, respectively. Handsheets were made from each revolution according to TAPPI standard T 205om-97, and then compared with control sample. Analysis of variance was conducted using completely randomized design, then mean values were compared using Duncan’s test, and finally the normalization equations were used to determine the best treatment. The results showed that increasing refining revolution increased burst, tensile and folding strength, brightness and density but decreased freeness, bulk, thickness, tear strength and opacity. Normalization equations showed that the best paper can be made from refining revolution of 9000.