جستجوی مقالات مرتبط با کلیدواژه « paper properties » در نشریات گروه « صنایع چوب و کاغذ »

In this study, the effect of cellulose nanofibers on the properties of handmade papers produced from hemp and wood pulp fibers was assessed. Also, the nanofiber application as a strength enhancer for restoration of handmade papers was investigated. Firstly, handmade paper samples were prepared. Cellulose nanofibers with weight percentages of 0.5, 1 and 2% were prepared as a suspension in water the samples were treated by the suspensions. Blank and treated samples were tolerated accelerated aging process and then pH, colorimetric and tensile strength tests were performed. Comparison of blank and treated samples results showed that the tensile strength of the both groups of hemp (H) and wood pulp (WP) papers were increased after treatment by cellulose nanofibers. Aging process caused to reduction in tensile strength of treated samples but it was increased in comparison with blank samples before and after aging. The pH of the papers in both groups was in the alkaline range after the treatment and aging. Brightness of papers was increased after the treatment and color changes in the samples were due to their accelerated aging conditions.

The aim of this study was to investigate the effect of using the protexin enzyme (percentage and repetition) as a probiotic agent on the properties of stored bagasse for pulp and paper production. For this purpose, the protexin was added at three concentrations of %0.125, %0.25 and %0.5 based on oven-dry weight of bagasse and two treatment times: once (adding protoxin at the beginning and storage for six months) and twice (adding protexin at the beginning and after three months). Then, the treatment bagasse was evaluated for physical properties (weight loss and pH), and chemical compositions. After that, soda pulp was done under active alkali 17%, cooking temperature of 170 °C and cooking time of 30 minutes. Finally, the properties of pulp and paper were measured and compared with green and control samples without treatment. Results showed that using of protexin enzyme with a concentration of 0.5%, twice resulted in the highest conservation status of stored bagasse in terms of the quality of the raw material and pulp and paper properties. In general, the greater the concentration and frequency of using of the enzyme protexin in bagasse storage, a greater improvement in the quality of bagasse and pulp and paper properties can be achieved.

In this study, the effect of alum- dispersed rosin sequence has been examined on different properties of papers made from recycled fibers. Therefore, reverse sizing recycled fibers with 0.5 consistency at pH6.5 was carried out by using 1 and 1.5 % alum, and 1, 1.5 and 2 % dispersed rosin, based on dry weight of pulp. Then, water absorption, optical and strength properties of papers with grammage (60±3 g/m2) were evaluated. Based on the results, to reduce the water absorption of papers, 1 % of both alum and dispersed rosin is required to achieve appropriate level of sizing. As a result, the water absorption of papers declined from 174±7.4 g/m2 to 36±0.4 g/m2, and the contact angle of water droplet with paper surface increased from 31.2 degree to 118.1 degree. Moreover, concurrent to the hydrophobicity of fibers surface formed by rosin molecules and its repellency impact of inter-fiber bonding, alum imparts an improvement of bonds in paper network owing to the neutralization of anionic trash and retention of cellulose fines. Paper opacity has been increased due to the development of filler retaining in fibrous web of paper.

Providing some paradox properties of paper products at the same is of utmost challenging issues of papermakers, e.g., attaining proper strength together with high water absorbency in hygienic papers. Because higher bonding resulted in lesser accessibility to the hydrophilic functional group. Therefore, hydrogel as an ever-increasing material in bulk cellulosic diapers were surficial coated on paper and compared with distillated water saturated papers. The prepared chitosan-acrylic acid (AA) hydrogel converted into nanoparticles by ultrasonic homogenizer and the nano scaled particles approved by Dynamic Light scattering (DLS). SEM images and paper caliper revealed the nanohydrogel coating layer. All papers water uptake coated with 1, 1.5 and 2% nanohydrogel increased significantly up to 50% compared to the untreated sample. Burst and dry tensile strengths along with water uptake improved, with no toleration in tear strength. Increased fiber bonding due to plenty of carboxylic acid in AA together with hydroxyl and amine groups in chitosan, along with nanohydrogel film formation as a complementary assembly and constituent with the cellulosic substrate of paper were resulted in strength improvement. Wet tensile strength of paper revealed remarkable increment at 2% coating application, only; without enhancing effects at the lower dosages. Paper opacity, brightness and whiteness stayed almost stable, but due to chitosan yellowish nature, the paper yellowness increased. The coated paper stiffness enhanced compared to untreated paper, but revealed lesser stiffness than water saturated papers. Water treated papers revealed caliper, tensile and burst indices reduction and stiffness rising.

Improvement the strength properties of papers made from recycled fibers is of important aims in papermaking industries. Current researches revealed that higher retention of strength induced additives through alternative absorption of polymers having opposite charge is one of promising approaches to obtain such purpose. In this study, treatment of fibers prepared from neutral sulfite semi-chemical papers with cationic starch and anionic CMC was conducted in pH~7, pH~10 and 0.001 M NaCl salty suspension. Then, fibers water retention value and zeta potential was measured. Standard handsheets with 60±3 g/m2 basis weight were made from untreated and treated pulps. The results have shown that fibers WRV significantly increased by absorbing of these two water-loving polymers. Consecutive changes of zeta potential confirmed charge reversion of fibers surface and sequential absorption of couple polymers. Scanning electron micrographs prepared from the samples of untreated and treated papers presented new variations in amount of fibers bend area due to the larger absorption of these two reinforcement polymers. Moreover, considerable development in paper mechanical characteristics (tensile, burst and tear indices) proved the success of high absorption of applied bio-polymers.

Nowadays, recycled fibers are the main fiber source for manufacturing packaging papers. Sizing of such papers, based on the type of application, is of great importance. In this research, the effect of alum-cationic rosin consumption amount in pH of about 6.5 on the properties of papers made from white sheets trimmings was examined. In order to optimize consumption extent, pulp suspension sizing with alum in six level of 0, 4, 5, 7, 8, and 10 %, and rosin with the ratio of 50 % of alum based on oven dry (OD) pulp was done according to the TAPPI standard methods. Then by preparation of handsheets with basis weight of about 65±5 g/m2, their Cobb test (45 second), structural and strength characteristics were investigated. Statistical analysis of the results have shown that alum and rosin consumption amount of about 7 and 3.5 % based on OD pulp is the best suitable level for internal sizing of white sheets trimmings fibers. In these alum-rosin level, Cobb value of papers decreased from 120±11.6 g/m2 the lowest value of about 64±9.7 g/m2. Contact angle of water droplet with the paper surface increased from 24.81º to 96.53º. Paper tensile index decreased up to 125±9.7 N.m/g by such sizing level and again increased with increasing alum-rosin level. Seemingly, such phenomena can be attributed to the alum role in charge neutralizing, cellulosic fines retention and improving bonding-ability of paper network. Meaningful decrease of paper surface roughness from 10.34±0.54 µm in control sample to 8.23±1.37 µm in sized papers in optimized level confirmed this assumption.

The aim of this study was to investigate the effect of using different fillers in the presence of cationic rosin sizing agent on the properties of pulp and paper made from CMP fibers. For this purpose, cationic rosin internal sizing agent at the levels of 0, 0.5, 1 and 1.5 % based on oven dry fibers, and fillers including grounded carbonate calcium (GCC), precipitated carbonate calcium (PCC), Talc and Zeolite in 25 % level based on oven dry paper accompanied with cationic polyacrylamide retention agent at the constant level of 0.3 % based on oven dry fibers were added to the CMP pulp suspension according to the TAPPI standard. In order to examine the effect of different fillers in the presence of cationic rosin, handsheets with basis weight of about 60±3 g/m2 were prepared from each experiment. Then, various pulp and paper characteristics were measured. Statistical analysis of the results revealed that type of filler has dissimilar behavior on the pulp and paper properties in the presence of cationic rosin. Drainage time of pulp suspension was lower when adding Zeolite and GCC fillers. Talc and PCC decreased more the paper strengths properties. Ultimately optical properties of papers improved more when Talc and PCC were added to the CMP pulp. Consequently, with respect to the priority of brightness and opacity for the copy and print papers made from CMP fibers, addition of Talc and PCC in the presence of cationic rosin sizing agent may be meet more the requirements compare to Zeolite and GCC fillers.

In the current study, modification of NSSC pulp broke fibers was done by forming starch polymeric multilayers, using Layer-by-Layer (LbL) layering method. After fiber slushing and preparation of pulp suspension with 0.5% consistency and conductivity formation of about 437 µS/cm, adding water solution of 1 mM NaCl, the experiments of fibers treatment were conducted to build the polymeric layers (up to 5 consecutive layers). Afterward, water retention value (WRV) of fibers was calculated in samples to evaluate the influence of this method on fibers hydrophilicity. The fibers were then used to prepare standard handsheets (60±3g/m2) and the physical and strength properties of sheets were evaluated as a function of the number of layers deposited on the fibers. The results showed that the WRV index of the fibers was improved by the LbL treatment of NSSC broke pulp fibers, due to the increase in starch electrostatic absorption. Successive variation in paper apparent density increase and paper thickness decrease confirmed the construction of starch multilayers on the surface of broke fibers. Formation of such multilayers on broke fibers has led to considerable improvement in tensile index (from 13.21 N.m/g to 30.65 N.m/g) and burst index (from 1.23 kPa.m2/g to 2.36 kPa.m2/g). Also, the prepared SEM micrographs approve the sheet web compaction and paper mechanical improvement resulted due to an increase in inter-fiber bonding.

Application of dry strength additives is regarded as a sustainable strategy toward improvement of recycle paper properties, and Bio-based materials utilization enhanced in this aspect extensively, respecting to different technological and environmental issues. In order to improving products properties, Cellulose and Chitosan as the most abundant biopolymers with unique characteristics, have been focused under ever increasing researches as natural and processed forms. Effects of the biopolymers, chitosan and nano fibrillated cellulose (NFC), individually and combined together on recycled pulp and paper properties showed that density and strength indices of paper (tensile, burst and tear), pulp drainage and retention during sheet formation improved with reduction in the material loss compared to the blank. Chitosan addition caused significant enhancement on all of the strengths, density and pulp retention and also reduction in material loss. Dewatering of the pulp suspension (CSF) was significantly improved by chitosan presence, with decline resulted from the higher addition level. The resulted developments were attributed to polymeric character, structural similarity and high bonding ability of chitosan with cellulosic fibers. Individually addition of NFC produced boost in the pulp retention, paper density, tensile and burst indices and fall in pulp freeness, material loss and tear index. Anionic nature, high specific surface area and hydrogen bonding ability of NFC were ascribed to these. Application of NFC just after chitosan as a complex mechanism in papermaking wet end not only had no increment in density and strength indices of recycled paper (except NFC 0.15%), reduced strengths in some cases. In the complex, the pulp properties were fluctuated compared to chitosan treatment, but were prior compared to nano fibrillated cellulose.

In this research, nano fibrillated cellulose, as a reinforcement nano material and environmentally biodegradable material which has recently attracted the attention of most researchers and paper producers, has been added to chemi-mechanical pulp used for manufacturing of liner board at different charges of 5, 20, 50 and 100% in two different levels of freeness. Also, the effect of wet press, one of the the most important processing agents on the properties of paper reinforced with nano fibrillated cellulose, in two levels of press pressure which included 3 and 6 bar, has been investigated. Finally, physical, barrier and strength properties of the papers produced have been measured according to TAPPI test methods. Addition of nano fibrillated cellulose was resulted in improved tensile and air resistance of chemi-mechanical pulp and increasing trend in improving of these properties with increase in press pressure was one of the important achievements of the present research.

The properties of catalyzed organosolv pulp obtained from maple juvenile wood were studied. The physical properties of fiber (e. g. length، width، and cell membrane thickness) and chemical composition of maple juvenile wood (e. g. average cellulose، lignin، extractives، and ash content) were determined. The variables were cooking temperature (190 and 200 ºC) and time (40، 60، and 80 minutes). Chemical charge (280 ml methanol، 70 ml water، and 0. 025 mols of Calcium Chloride and Magnesium Nitrate) was kept constant. Pulp screen yields (54. 9 to 60. 91%) and Kappa No. (15. 5 to 18. 4) were measured. Pulp freeness was reduced to 350 ml CSF in PFI mill، and ten 60 g/m2 handsheets were made from the selected pulps. The strength properties of catalyzed organosolv handsheets including tear length (3. 83 to 4. 25 km)، tear index (10. 22 to 12. 81 mN. m2/g)، and burst index (1. 74 to 2. 15 kPa. m2/g) were compared with those of the conventional Kraft handsheets of maple juvenile wood. The least allowed values of the mentioned properties in the Indian (IS) and Japanese international standards (JIS) reveal that while the tear length value is slightly below that of the standards، the values of tear and burst indices are well beyond the given standards، and the environmentally-friendly catalyzed organosolv pulping process (higher yield and lower Kappa No. compared to Kraft) can be recommended to produce paper pulp from maple juvenile wood.

This research was conducted to find a procedure to increase the optical and strength properties of papers made from oxidized waste newspaper fibers. Samples of waste newspapers were randomly selected and deinked, then one part of deinked pulp was refined. Both refined and unrefined recycled pulp were divided into two groups. In each case, a group of pulps was used to make standard hand sheets (control samples) without hydrogen peroxide treatment and only adding 2% cationic starch. Second group was subjected to different percentages of hydrogen peroxide (2%, 3% & 4%) in alkaline conditions, then 2% cationic starch was added to oxidized fibers prior to hand sheeting preparation and then standard hand sheets were made. Opticaland strength properties of all hand sheets were determined according to TAPPI standards. Also FTIR spectra was taken to specify the effect of oxidation on surfaces of pulp fibers. Results showed that treatment with oxidizing agent increased the strength indices of papers. This increase was more evident when 3% hydrogen peroxide was applied. The strengths of the control samples were the lowest. Moreover, refining imposed the positive effect on strength properties. Results of optical properties measurements indicated that as the extent of treatment for both refined and unrefined pulps increases, the brightness increased, and both the yellowness and opacity decreased. The highest brightness was reached when 3% peroxide was used. Also refining results in increased in brightness and yellowness but decreas opacity. FTIR spectra showed that samples of oxidized pulp had the greatest absorption at wave number of 1650 which pertains to carboxyl group.