Properties Of Paper Sheets Research Articles

Sudanese Agro-residue as a Novel Furnish for Pulp and Paper Manufacturing

Sudan has rich sources of lignocellulose materials from agricultural waste that have potential to be used as a papermaking furnish following adequate chemical compositions, elemental analysis, fibre dimensions, and morphology of millet stalks and date palm leaves. Paper sheet properties from the various pulps made were investigated, and it was found that there was no difference in the polysaccharide (cellulose and hemicelluloses) content between millet stalks and date palm leaves, although millet stalks had a high lignin content of 18.20% relative to date palm leaves’ content of 15.34%. Moreover, millet stalks showed a high pulp yield (42.04%) with a viscosity of 665 mL/g compared to that (34.43%, 551 mL/g) and (38.50% and 534 mL/g) of date palm leaves and the blend, respectively. Papers produced from date palm leaves and millet stalk blends showed better physical properties compared to that of pure millet stalks and date palm leaves. The Scanning Electron Microscopy (SEM) analysis showed that fibres in the blend were more closely packed than that of the pure millet stalks and date palm leaves fibers. Based on their physical and chemical composition properties, millet stalks and date palm leaves have a high potential as a furnish for pulp and papermaking.

Preparation of Paper Strengthening Agent by Esterification of Cellulosic Fines

Paper strengthening agents play an important role in the papermaking industry with the increase of secondary fiber applications. The objective of this study was to create a dry-strength agent by esterification. The fines from the pulp were collected and modified with trimesic acid and citric acid, respectively, to obtain the dry-strength agent. The influences of acid type and dosage on the enhancing effect were investigated. Compared with the control sample, the physical properties of paper sheet were improved after adding modified fines. The properties of recycled paper were also improved by the modified fines. When the dosage of citric acid agent was 7%, the effect on paper properties saw the greatest improvement. The tensile index, burst index, and folding endurance were increased by 60.3%, 18.3%, and 146.2%, respectively, compared with the control. The improvement of paper properties was due to the increase of carboxyl content in the modified fines. Based on the findings, it can be concluded that the esterification is an effective approach for producing paper dry-strengthening agent.

Engineering microfluidic papers: determination of fibre source and paper sheet properties and their influence on capillary-driven fluid flow

In the present study, the surface chemistry of fibres from different sources (groundwood, cotton linters, eucalyptus sulphate and a mixture of pine sulphate and spruce sulphate) was initially assessed via inverse gas chromatography. Significant differences were revealed among the four fibre types, especially between groundwood and the other three with regard to the surface energy and to the specific component of the work of adhesion of different polar probes. Moreover, the freeness value and the specific surface area of the diverse fractionated and unfractionated fibrous materials were investigated. In addition, the porosity and the pore size distribution of lab engineered paper sheets produced with the previously mentioned fibre sources were studied while modifying the fibre length and grammage. Novel approaches to modulate and control fluid transport in the lab-engineered paper substrates were introduced by using different fibre sources with the same freeness value, by fractionating the fibres before fabricating the paper substrates, and by changing the orientation of the fibres. The experimental results for our lab-engineered paper substrates and commercially available filter paper were compared with each other. Our findings suggest a considerable improvement in liquid transport velocity of tailor-made microfluidic paper based analytical devices with lab-engineered paper substrates. By altering the mentioned fibre and paper values, we managed to reduce or raise the capillary rise, which eventually allows us to modulate and control fluid flow in a more accurate and desirable way. Finally, changes in the fluid transport for paper substrates laid on materials with different water contact angles were tested. The obtained information thereby provides an alternative method to increase or decrease the capillary rise.

Photocatalytic activity and antimicrobial properties of paper sheets modified with TiO2/Sodium alginate nanocomposites

Photocatalytic paper sheets were prepared by addition of different ratios of TiO2/Sodium alginate (TSA) nanocomposite. The modified paper sheets were characterized by XRD, TGA. Their morphology was studied by scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Photocatalytic activity of modified paper has been studied by analysis of chemical oxygen demand (COD) of waste-water. The results confirmed the mineralization of the waste-water and enhanced removal of chemical oxygen demand (COD) by increasing the amount of photocatalyst in the paper. Moreover, the results also confirmed that presence of sodium alginate as biopolymer increased adhesion of nanoparticles to paper fibers and reduced the harmful effect of the photocatalyst on them. The paper sheets containing 7% as well as 15% TSA showed high photocatalytic activity and anti-bacterial effect against Salmonella typhimurium higher than standard antibiotic beside other microorganisms such as Candida albicans. The maximum antimicrobial effect was found in case of specimen loaded with 15% TSA. Moreover, it was found that by adding 20% TSA to the paper matrix, the properties of the paper composite collapse. The obtained results confirm the possible utilization of the modified paper in both hygienic and food packaging applications.

Novel nanofibrillated cellulose/chitosan nanoparticles nanocomposites films and their use for paper coating

Novel nanocomposites films were prepared from TEMPO-oxidized nanofibrillated cellulose isolated from rice straw, chitosan nanoparticles (CHNP), and glycerol by solution casting. The percentage of chitosan nanoparticles ranged from 2.5 to 20% while a fixed ratio of glycerol (25%) was added. The effect of chitosan nanoparticles on porosity, tensile strength properties, water vapor permeability, grease-proof, and antimicrobial properties was studied. The results showed that addition of chitosan nanoparticles can improve tensile strength properties, reduce porosity, and impart NFC antimicrobial properties against Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli), and yeast (Saccharomyces cervisiae). CHNP did not affect WVP or grease-proof properties of NFC films.The mixture containing CNF and 10% CHNP was used for paper coating and the effect of coating on tensile strength, porosity, water vapor permeability, water absorption, and grease-proof properties of paper sheets was studied. The results showed coating of paper sheets with thin film of NFC or NFC/CHNP can improve tensile strength properties, decrease porosity and water absorption, and increase grease-proof properties of paper sheets but did not affect their WVP. Presence of CHNP in the coating mixture resulted in higher tensile strength properties of coated paper sheets than in case of using NFC alone but no noticeable differences were found regarding porosity, WVP, grease proof, and water absorption of paper sheets coated with NFC or NFC/CHNP under the conditions used.

The influence of TiO2/CC core/shell pigments on the properties of paper sheets

In this work, new core-shell pigment based on precipitating a small amount of titanium dioxide on precipitated calcium carbonate (CC) were applied once as filler in paper sheet making and another time was mixed with chitosan as a coat on the papers. The prepared pigments were characterized to confirm their preparation. The mechanical and optical properties of both filled and coated paper sheets and their individual components (TiO2 and CC) were performed to compare their effect on the paper sheets using SEM, TGA and UV aging.

Papermaking potential of Citrus sinensis trimmings using organosolv pulping, chlorine-free bleaching and refining

One of the most popular ways to carry out the re-use of wastes from agriculture is the pulping, refining and bleaching of those residues for papermaking. Spain annually produces more than 300 thousand tonnes of Citrus sinensis (orange tree) trimmings, crops being concentrated in the East and the South of the country. Their chemical composition is similar to that of common hardwoods.This work aims to show the suitability of ethanolamine cooking when applied to orange tree trimmings, and to study the effect of peroxide bleaching and refining on some key properties. As for bleaching, we used a design of experiments to discuss the influence of peroxide concentration, time and temperature on the yield, brightness, viscosity, kappa number of pulps and mechanical properties of paper sheets. Refining was studied by analysing the diminishment in freeness and the mechanical properties of paper sheets formed. Results showed that even a mild bleaching process gives out a high relative brightness gain, but a multiple-step process is necessary to achieve enough brightness for printing paper. Mechanical properties of non-refined pulps were found to be too low for paper of any grade, but they were greatly improved by refining.

Cross-Linking Cellulosic Fibers with Photoreactive Polymers: Visualization with Confocal Raman and Fluorescence Microscopy.

The properties of paper sheets can be tuned by adjusting the surface or bulk chemistry using functional polymers that are applied during (online) or after (offline) papermaking processes. In particular, polymers are widely used to enhance the mechanical strength of the wet state of paper sheets. However, the mechanical strength depends not only on the chemical nature of the polymeric additives but also on the distribution of the polymer on and in the lignocellulosic paper. Here, we analyze the photochemical attachment and distribution of hydrophilic polydimethylacrylamide-co-methacrylate-benzophenone P(DMAA-co-MABP) copolymers with defined amounts of photoreactive benzophenone moieties in model paper sheets. Raman microscopy was used for the unambiguous identification of P(DMAA-co-MABP) and cellulose specific bands and thus the copolymer distribution within the cellulose matrix. Two-dimensional Raman spectral maps at the intersections of overlapping cellulose fibers document that the macromolecules only partially surround the cellulose fibers, favor to attach to the fiber surface, and connect the cellulose fibers at crossings. Moreover, the copolymer appears to accumulate preferentially in holes, vacancies, and dips on the cellulose fiber surface. Correlative brightfield, Raman, and confocal laser scanning microscopy finally reveal a reticular three-dimensional distribution of the polymer and show that the polymer is predominately deposited in regions of high capillarity (i.e., in proximity to fine cellulose fibrils). These data provide deeper insights into the effects of paper functionalization with a copolymer and aid in understanding how these agents ultimately influence the local and overall properties of paper.

English

This study investigated the potency of sweet sorghum ( Sorghum bicolor ) bagasse as raw material for pulp and paper using kraft pulping. The effects of alkali and sulfidity loading on kraft pulp and paper properties were also investigated. The pulping condition of the kraft pulp consisted of three levels of alkali loading (17, 19 and 22%) and sulfidity loading (20, 22 and 24%). The maximum cooking temperature was 170°C for 4 h with a liquid to wood ratio of 10:1. Kraft pulping of this Numbu bagasse produced good pulp indicated by high screen yield and delignification selectivity with a low Kappa number (< 10). The unbleached pulp sheet produced a superior brightness level and a high burst index. The increase of active alkali loading tended to produce a negative effect on the pulp yield, Kappa number and paper sheet properties. Therefore, it is suggested to use a lower active alkaline concentration.

Micro-nanoparticle gels obtained from bark for their use alone and with chitosan and Na-CMC in paper coatings

Abstract The effect of coatings on paper sheets has been studied. For this purpose gels were prepared from unextracted and extracted bark. The gels represented dispersions of micro- and nanoparticles. The coatings were also prepared from mixtures of gels with chitosan solutions in 1% acetic acid and aqueous Na-carboxymethylcellulose (Na-CMC) solutions. The properties – Gurley air resistance, water vapour sorption, and mechanical properties of paper sheets – were tested. For obtaining the gels, the bark was destructed by a thermocatalytic method and then dispersed in water in a ball mill. The gels contained mainly nanoparticles with an average size of about 300 nm. Paper sheets produced by the Ligatne Paper Mill (Latvia) were coated on both sides. Gurley air resistance increases with increasing thickness of the coatings and with increasing gel concentration. At a gel concentration of 10% and a coating thickness of 35 μm, air resistance increases by 57% (gel from unextracted bark) and 72% (gel from extracted bark) compared to uncoated paper sheets. The coatings from bark gels in combination with Na-CMC and chitosan solutions increase further the air resistance. The coatings at gel concentrations up to 6% elevate the burst strength and tensile strength in a dry state. The coatings from mixtures of bark gel and chitosan and Na-CMC heighten further the mechanical properties and elevate the water vapour sorption of paper sheets.

Barley Straw (Hordeum vulgare) as a Supplementary Raw Material for Eucalyptus camaldulensis and Pinus sylvestris Kraft Pulp in the Paper Industry

The present study shows that barley straw (Hordeum vulgare) can be a supplementary raw material of softwoods and hardwoods such as Pinus sylvestris and Eucalyptus camaldulensis, respectively, for the production of cellulose and paper, reducing an agricultural residue that has no added value. Barley straw has a lower content of cellulose at 36.4% than P. sylvestris and E. camaldulensis, but it contains a lower quantity of lignin, 15.9%. After pulping with soda anthraquinone (AQ), high contents of cellulose (56.5 to 67.5%) and holocellulose (>80%) were attained. Paper sheet properties were able to reach, and even improve upon, those of wood species (Pinus and Eucalyptus) pulped with kraft. Better values of total yield (56.5%), Kappa number (8.9), and ISO brightness (36.4%), were attained for paper sheets from barley straw pulp versus E. camaldulensis and P. sylvestris, respectively, and comparable values for viscosity, tensile, and burst index were obtained.

Structure and Properties of Chitin Whisker Reinforced Papers for Food Packaging Application

In recent years, concerns about environmental waste caused by petroleum-derived chemicals as well as the consumer's demand for high quality food products, have prompted people to pay more attention to developing biodegradable food packaging materials using natural resources such as cellulose fibers and chitin derivatives. In this study, chitin whiskers have been successfully generated by hydrolyzing the α-chitin sample. Then the synthesized nano-sized chitin whiskers were used at ratios from 0.1% to 2% (wt%) for improving strength properties of paper sheets by the dip-coating method. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) were used to investigate the morphology of chitin whiskers and cellulose fiber compounds. The results showed that coating with chitin whiskers brought about an increase in tear strength, burst strength, and wet and dry tensile strength, with a decrease in Zeta-potential value.

Modification of wollastonite by acid treatment and alkali-induced redeposition for use as papermaking filler

In order to increase the applicability of wollastonite in the papermaking industry, it was modified by an acid treatment and alkali-induced redeposition. The modification process consisted of two steps: first, sulfuric acid was mixed with wollastonite, resulting in the partial dissolution of the wollastonite particles. Next, the pH of the mixture was adjusted to make it alkaline so that the dissolved material was redeposited on the surfaces of wollastonite particles, which maintained their original acicular morphology. The resulting wollastonite particles were larger, had a higher zeta potential, and were brighter than were those of the original sample. The properties of paper sheets, especially bulk and brightness, in which a Na2SiO3-induced redeposited wollastonite sample was used as the filler were superior to those in which the original wollastonite sample or other alkali-induced redeposited wollastonite samples were used.

Chemical pulping of waste pineapple leaves fiber for kraft paper production

The main objective of this study is to evaluate the implementation of acetone as a pulping agent for pineapple leaves. Mixtures of water and acetone with concentration of 1%, 3%, 5%, 7%, and 10% were used. The effects of soaking and delignification time on the paper properties were investigated. Thermal and physical properties of paper sheet were studied using thermogravimetric analysis (TGA) and tearing resistance test respectively. The morphological properties were observed using microscope at 200× magnification. The paper sheet produced from pulping with 3% acetone concentration shows the highest mechanical properties. Papers strength was improved by increasing the delignification time. The delignification time was reduced by cooking the pineapple leaves at a temperature of 118°C under applied pressure of 80kPa which has remarkable effect on paper strength.

Surface modification of natural fibers by plasma for improving strength properties of paper sheets

Abstract Fibers of aspen chemi-thermomechanical pulp (CTMP), spruce CTMP, bleached kraft pulp (BKP), and kraft pulp were treated by low-temperature plasma (air) aiming at the detection of the relationship between chemical components on the surface and the properties of sheets. The effects of plasma treatment were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy. The results show that the strength properties of sheets, especially the wet-tensile strength, were significantly improved, while optical properties were scarcely affected. Aspen and spruce CTMPs with abundant lignin and extractives were sensitive to plasma treatment in that the O/C ratio increased and lignin or extractive contents decreased. However, the crystallinity of BKP evidently decreased after plasma treatment owing to carbohydrate enrichment on the surface. Compared to the partial removal of noncarbohydrates through a laccase/mediator system, plasma treatment did not remove them in large amounts but created more carboxyl and hydroxyl groups, which improved the strength properties of paper sheets.

Predicting hygro-elastic properties of paper sheets based on an idealized model of the underlying fibrous network

Significant dimensional variations may occur in paper-based materials when subjected to changes in moisture content. Moisture induced deformations are governed by the swelling of individual fibres, which is transferred through inter-fibre bonds to the entire fibrous network. Complex interactions between mechanical and hygro-expansive properties take place in the bonding areas, affecting the overall material response. In most network models, the role of these inter-fibre bonds is not explicitly incorporated. This work presents a periodic meso-structural model for the discrete fibrous network, which considers the free-standing fibre segments and inter-fibre bonds. Despite its simplicity, the reference unit-cell enables the incorporation of relevant micro- and meso-structural features such as network structure, fibres and bond geometry and hygro-elastic properties. The proposed model is solved analytically through a proper homogenization strategy, allowing to recover the paper’s anisotropic hygro-mechanical response in terms of effective elastic constants and effective hygro-expansive coefficients, exploiting the coupling at the meso-structural level between hygroscopic and mechanical behavior. A comparison with experimental results obtained from the literature shows that the presented approach is quite accurate in predicting the overall paper response, thereby revealing the influence of several meso-scale parameters (e.g. fibre orientation, dimensions, mechanical strength).

Palm rachis microfibrillated cellulose and oxidized-microfibrillated cellulose for improving paper sheets properties of unbeaten softwood and bagasse pulps

Bleached palm rachis pulp, pretreated with xylanase enzymes, was used for isolation of microfibrillated cellulose (MFC) and TEMPO-oxidized MFC (TMFC) by ultrafine grinding. The isolated MFC and TMFC were used at ratios from 2.5% to 20% for improving strength properties of paper sheets prepared from unbeaten softwood and bagasse pulps. The retention of microfibrillated cellulose in paper sheets was also estimated. The results showed that MFC or TMFC brought about an increase in density, wet and dry tensile strength, tear resistance, and a decrease in air permeability of paper sheets prepared from unbeaten softwood or bagasse. However, usual beating of softwood fibers was much more effective in improving strength properties of softwood paper sheets than addition of microfibrillated cellulose. On the other hand, the improvement in strength properties of bagasse paper sheets as a result of MFC or TMFC addition was generally higher than that resulted from beating of bagasse pulp. Use of TMFC with unbeaten softwood or bagasse fibers resulted generally in better improvement in tensile strength (wet and dry) than in case of using MFC.

Improvement in Strength and Vapor Barrier Properties of Cellulose Composite Sheets with Chitosan and Carboxymethyl Cellulose

<abstract> <bold><sc>Abstract. </sc></bold>Improvement in the dry strength, wet strength, and vapor barrier properties of paper sheets has been shown through the sequential addition of chitosan (CS) and carboxymethyl cellulose (CMC) to the pulp solution. Examination of pulp solutions revealed the formation of aggregates due to electrostatic interaction between the unabsorbed CS and CMC. Tensile test results revealed 64% improvement in the dry modulus for sheets with 50% CS and 50% CMC with respect to the control sheet. The wet tensile test results showed that the control pure pulp sheet broke immediately, whereas the composite sheet with 50% CS and 50% CMC exhibited a wet modulus value of 39.5 MPa. The specific water vapor transmission rate (SWVTR) was also found to be the lowest for this particular composite, with a 32% decrease with respect to the control sample, which was again attributed to the formation of agglomerates that filled the void spaces.

Enhancing both the mechanical and chemical properties of paper sheet by graft co-polymerization with acrylonitrile/methyl methacrylate

The chemical graft copolymerization reaction of acrylonitrile (AN) and methyl methacrylate (MMA) binary mixture onto paper sheet was performed. The effect of initiator concentration, monomer concentration and temperature on the reaction rate was studied. The reaction rate equation of the graft copolymerization reaction is found to be RP = K2 [Initiator]0.795[Monomer]2.007. The apparent activation energy (Ea) of the copolymerization reaction is found to be 75.01 kJ/mol. The infrared characteristic absorption bands for cellulosic paper structure and the paper gr-AN-MMA are investigated. Tensile break load, porosity and burst strength were measured for the grafted and pure paper sheet. It was found that the mechanical properties are improved by grafting copolymerization. The chemical resistance of the graft product against a strong acid a strong alkali, polar and nonpolar solvents was investigated. It was found that the resistance to these chemicals is enhanced by grafting.

Engineering microfluidic papers: effect of fiber source and paper sheet properties on capillary-driven fluid flow

In the present study, we introduce a novel approach to control and modulate fluid transport inside microfluidic papers using lab-engineered paper sheets. Lab-sheets consisting of different fiber sources (eucalyptus sulfate and cotton linters pulp) and varying porosities were designed and further modified with small millimeter-scaled channels using hydrophobic barriers consisting of fiber-attached, hydrophobic polymers. The capillary-driven transport of an aqueous solution was monitored visually, and the influence of parameters such as fiber source, paper grammage, and channel width on the flow rates through the channel was investigated. The experimental results were compared with those obtained with commercially available filter papers. Our findings suggest that accurate control of fluid transport processes with standard filter papers is complex. Additionally, if the channel width is smaller than the mean fiber length, flow rates become dependent on the geometric parameters of the channel because of the formation of dead-end pores at the hydrophobic barriers. Finally, control of the paper sheets porosity, by varying the fiber density of the lab-made paper, affords the fabrication of chemically identical sheets whereby capillary flow is largely influenced and can be modulated accordingly by simple papermaking processes.