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This work has focused on oxygen’s role in the delignification process within the context of pulp production. We have investigated the role of oxygen in a complex set of chemical reactions taking place during this process, including both oxidative and non-oxidative reactions. This study explores the impact of pH changes during the oxygen delignification process and the characteristics of the resulting pulps. Additionally, this research examines the effect of oxygen, by comparing conventional oxygen delignification with trials using air and nitrogen. Industrial softwood kraft pulps with a kappa number of 35 were subjected to delignification for 20–120 min under alkaline conditions. The resulting pulps were assessed for kappa number, intrinsic viscosity, fiber charge, and ISO brightness. An important observation from this research is the reduction in lignin molecular weight upon exposure to oxygen and air, suggesting depolymerization reactions facilitated by oxygen species, whereas nitrogen exposure results in less pronounced changes. This finding underscores the impact of oxygen in altering lignin structure, thus informing the selectivity and effectiveness of the delignification process. [ABSTRACT FROM AUTHOR]

For sustainable use of lignocellulosic resources, pruned tree branches of cocoa, one of the major evergreen tropical tree crops with significant economic importance worldwide, were investigated as a potential source of kraft pulp. This study determined the chemical composition, fiber dimensions, kraft pulp, and paper properties of the cocoa tree (Theobroma cacao L.) branches compared to the deciduous trees traditionally used in the paper industry. A handsheet of cocoa pulp showed promising results with narrow fiber length distribution, high paper density, and high mechanical strength. The yield of kraft pulp made from cocoa branches wood was lower. The tensile and burst indices of cocoa pulp handsheet were 2 and 2.5 times higher than that of hardwood traditionally used in the paper industry. These results suggest a potential use of cocoa (Theobroma cacao L.) tree branch wood for pulp production using the kraft process. [ABSTRACT FROM AUTHOR]

This study investigates the role of secondary condensates in the pulp and paper industry's journey to minimize its water footprint. The integration of secondary condensates, traditionally less explored in bleaching processes, is examined for its potential in reducing freshwater demand. Condensates with different organic content (chemical oxygen demand, COD) and their mixtures were tested as washing liquid after the alkaline extraction stage (EP) of eucalyptus globulus kraft pulp and compared to hot water. Two subsequent chlorine dioxide stages were applied to evaluate the impact of the washing liquid COD on pulp properties and chemicals consumption. Despite its higher organic content, the condensates can be used as a partial or total substitute for hot water without substantial compromises in the pulp properties, such as brightness, reversion, and viscosity. The calculated correlation between ClO2 consumption and COD in the washing liquid can be applied for assessing economic and environmental trade-offs, providing a roadmap for optimizing processes and reducing environmental impacts. [ABSTRACT FROM AUTHOR]

For sustainable use of lignocellulosic resources, pruned tree branches of cocoa, one of the major evergreen tropical tree crops with significant economic importance worldwide, were investigated as a potential source of kraft pulp. This study determined the chemical composition, fiber dimensions, kraft pulp, and paper properties of the cocoa tree (Theobroma cacao L.) branches compared to the deciduous trees traditionally used in the paper industry. A handsheet of cocoa pulp showed promising results with narrow fiber length distribution, high paper density, and high mechanical strength. The yield of kraft pulp made from cocoa branches wood was lower. The tensile and burst indices of cocoa pulp handsheet were 2 and 2.5 times higher than that of hardwood traditionally used in the paper industry. These results suggest a potential use of cocoa (Theobroma cacao L.) tree branch wood for pulp production using the kraft process.

An assessment has been made of the relationship between viscosity and mechanical strength of industrial samples of bleached hardwood kraft pulp. To produce this type of semi-finished product, birch and aspen wood has been used, which has been harvested in the Northwestern region of the Russian Federation. The viscosity of a solution of high-molecular polymers provides an idea of the average length of the fibers and, accordingly, their degree of destruction. In turn, the mechanical properties of the fibrous semi-finished product and the strength of the products made from it largely depend on the length of the fiber. Since it takes no more than 2 hours to determine the viscosity of a solution of high-molecular polymers, and 8–10 hours to obtain standard mechanical strength characteristics, viscosity analysis can be considered an express method that provides information on the mechanical strength of a semi-finished product. In this work, the ISO 5351:2010 international standard in cupriethylenediamine solution has been used to analyze the viscosity of the semi-finished product. High values of mechanical strength characteristics have been detected for industrial samples of bleached hardwood kraft pulp with a viscosity of more than 800 ml/g. For pulp samples, a correlation has been established only between the number of double folds and viscosity. Further research has been carried out on samples of bleached hardwood kraft pulp with different degrees of fiber destruction, which have been produced with varying the parameters of sodium hypochlorite treatment. The results have made it possible to establish a range of critical viscosity values for bleached hardwood kraft pulp, which has amounted to 600...700 ml/g, and a polynomial relationship between tear resistance, breaking length, a number of double folds and viscosity with a high confidence coefficient of data approximation of no less than 0.89. It has been shown that viscosity can become an analytical tool in the express diagnostics of the mechanical strength of a fibrous semi-finished product at the intermediate stages of production of bleached hardwood kraft pulp and in quality control of the ready-made semi-finished product.

In this study, the impact of mercerization and PFI refining on the properties of softwood kraft pulp was investigated. Never-dried softwood kraft pulp was treated with 15 wt% NaOH to generate highly hydrated fibers, followed by PFI refining to increase pulp fibrillation and porosity. The original and modified pulp properties were assessed for morphological and chemical composition. Differential scanning calorimetry (DSC) tests and water retention value (WRV) measurements were conducted to evaluate pulp swelling behavior and porosity. Fiber bonding potential and strength properties were evaluated from handsheets of mercerized and unmercerized pulp. Mercerization with 15 wt% NaOH successfully converted cellulose I to cellulose II, leading to slightly increased pulp swelling and micropore volume. However, the mercerization reduced handsheet strength properties. Furthermore, PFI refining resulted in a negligible enhancement of bonding in mercerized pulp, in stark contrast to its significant effect on unmercerized kraft pulp. [ABSTRACT FROM AUTHOR]

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Hygroexpansion, CP/MAS 13C-NMR, WAXS and SAXS measurements were carried out on sheets made from four different commercial pulps of varying lignin content. Non-directional laboratory sheets were made at different press levels from the pulps following different degrees of beating. The sheets were dried both freely and with restraints. Measurements were made on sheets before and after moisture cycling to determine hygroexpansion coefficients, changes in cellulose average lateral fibril dimensions and average cellulose crystallite sizes, with the aim of understanding macroscale and nanoscale changes as the result of moisture cycling. Within the sheets consistent and statistically significant structural changes were observed on both macro and nanoscale. On the macroscale, moisture cycling consistently induced irreversible shrinkage in sheets dried with restraints, but less so in the case of sheets dried freely. The hygroexpansion coefficients were typically higher for freely dried sheets compared with sheets dried with constraints. On the nanoscale, moisture cycling consistently caused an increase in the average crystallite sizes (WAXS) and the average lateral fibril dimensions (CP/MAS 13C-NMR), though the latter occurred with poor statistical significance. These changes were interpreted as an increase in the degree of order in the cellulose fibril interior/cellulose crystallite. There were no profound differences in the nanoscale changes observed for sheets dried with restraints and for sheets dried freely. Changes in the fibre wall nanostructure were of similar magnitudes when comparing results from freely dried low grammage sheets (less abundant inter-fibre joints) with freely dried sheets of higher grammage (more abundant inter-fibre joints). No obvious correlations were found between the macroscale and nanoscale measurements. The proposed explanation for this was that the nanoscale structural changes occurred similarly throughout the entirety of the fibre wall, independent of the proximity to an inter-fibre joint, and that the nanoscale structural changes were mainly the result of water penetrating into the interior of cellulose fibril aggregates. By using the same fibril model for evaluation of CP/MAS 13C-NMR and WAXS data, good-to-reasonable agreement were found for estimates of the degree of cellulose crystallinity. [ABSTRACT FROM AUTHOR]

The growing concern for a safer chemical industry has spurred research towards replacing strong acid solvents, because of the significant hazards they cause, such as issues related to effluent treatment and high corrosiveness. In the production of nanocellulose, sulfuric acid stands out as an example, being highly corrosive, yet widely used. This study aimed to investigate a more ecological acid mixture solvent, specifically comprising hydrochloric acid (HCl) and citric acid (CA), for obtaining carboxylated nanocellulose from kraft cellulose pulp. Distinct methodologies were employed based on three different durations, corresponding to each methodology (30 minutes, 60 minutes, and 90 minutes). FTIR analysis confirmed the occurrence of chemical modification. Among these methodologies, ultrasonication for 60 minutes yielded the best carboxylated nanocellulose, as determined through morphological analysis, with an average diameter of 8.4 nm and an average length of 123 nm. X-ray diffraction (XRD) revealed a decrease in crystallinity; however, both kraft pulp and carboxylated nanocellulose exhibited the cellulose Iβ allomorph. This surface modification paves the way for incorporating new functional properties into the design of composites, hydrogels, Pickering emulsions, drug delivery systems, food packaging, and biofilms. [ABSTRACT FROM AUTHOR]

Context: In Uruguay, numerous Pinus taeda plantations are at final-turn age, but they still do not have commercial destination and are exported as green-wood logs. For the development of this sector, it is necessary to strive towards a comprehensive processing of this resource. Method: This work focused on analyzing the use of Pinus taeda wood available in the country to produce brown kraft pulp with a kappa number of 80, which can be used to make packaging paper. As raw materials, we employed by-products from the mechanical wood-transformation industry (wood chips and thinning wood) and final-turn wood. Pulping tests were carried out, varying the alkali charge and the H-factor while aiming for a kappa number of 80. The viscosity, pulping, and rejection yield were measured in the pulps, and the pH and residual alkali content were evaluated in black liquor. Results: Based on the results, the best pulping conditions were an active alkali charge of 14% (Na2O) and an H-factor of 1260 for sawmill chips and thinning wood, as well as an active alkali charge of 14% (Na2O) and an H-factor of 1080 for final-turn wood. The pulp obtained with sawmill chips exhibited the most resistant fibers, and the final-turn wood pulp was the most sensitive to the refining process. Under the aforementioned conditions, the paper properties of laboratory-produced pulp are comparable with those of commercial pulp. Conclusions: This indicates that it is technologically possible to produce brown kraft pulp from Uruguayan Pinus taeda wood, with adequate quality to produce packaging paper

Africa is the third-richest continent in the world in terms of bamboo species. Despite these laudable natural resources, most African countries still use asbestos cement board as one of their major building materials. This is chiefly due to the high cost of equipment and technologies associated with non-asbestos-fiber cement board production. The current research seeks to underscore the possibility of utilizing these massive continent resources for non-asbestos-fiber cement board production by employing the existing production process in the asbestos cement industries via an innovatively developed laboratory-simulated Hatschek process. Non-asbestos-fiber cement boards incorporating kraft and bamboo fibers were successfully produced in the laboratory using this innovative method based on Hatschek technology, with natural fibre addition in the range of 2–6 wt.%. Experimental results revealed that the Flexural strength and deflection of the board improved significantly, producing optimum values of 10.41 MPa and 2.0 mm, respectively for composite board reinforced with 10 wt.% and 6 wt.% of kraft pulp and bamboo fibers, respectively. The SEM morphology of the fractured surfaces revealed the mode of composite fracture as well as good interaction at the fiber–matrix interface. Overall, the mechanical properties of the developed composite boards satisfy the minimum requirements of relevant standards based on fiber cement flat sheets and can be employed for internal building applications in low-cost housing estates in developing countries. The outcome of this research indicates that the current industrial production process based on Hatschek technology can be employed for non-asbestos-fiber cement board production using the studied natural fiber. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate new materials from organosolv fibers, organosolv lignin, kraft fibers, and their blends. The organosolv fibers showed reprecipitated lignin on the surface, a comparably low fiber length of 0.565 mm on average, and a high fines content of 82.3%. Handsheets were formed and thermopressed at 175 °C and 50 MPa, yielding dense materials (1050–1100 kg/m3) with properties different to that of regular paper products. The thermopressing of organosolv fibers alone produced materials with similar or better tensile strength (σb = 18.6 MPa) and stiffness (E* = 2.8 GPa) to the softwood Kraft reference pulp (σb = 14.8 MPa, E* = 1.8 GPa). The surface morphology was also smoother with fewer cavities. As a result, the thermopressed organosolv fibers exhibited higher hydrophobicity (contact angle > 95°) and had the lowest overall water uptake. Combinations of Kraft fibers with organosolv fibers or organosolv lignin showed reduced wetting and a higher density than the Kraft fibers alone. Furthermore, the addition of organosolv lignin to Kraft fibers greatly improved tensile stiffness and strength (σb = 23.8 MPa, E* = 10.5 GPa), likely due to the lignin acting as a binder to the fiber network. In conclusion, new thermopressed materials were developed and tested, which show promising potential for sustainable fiber materials with improved water resistance. [ABSTRACT FROM AUTHOR]

Nowadays, the emphasis is on increasing the durability of all products. For this reason, it is also advisable to look into extending the durability of paper products. The main reason for using flax pulp is that flax and cotton pulp are widely used for the production of banknotes due to their higher strength. This paper deals with flax pulp with the addition of nanocellulose, which should further enhance the mechanical properties of the pulp. The tensile strength, breaking length, and tensile energy absorption index were evaluated as the key mechanical properties. At the same time, the effect of the addition of nanocellulose, whether it was added to the pulp mass or applied to the later produced paper as a spray or coating, was tested in comparison to paper without the addition of nanocellulose. The best mechanical properties, i.e., tensile strength, were achieved for the highest addition of 5% of nanocellulose into the pulp, at 24.3 Nm∙g−1, and for the coating application, at 28.7 Nm∙g−1, compared to the flax pulp without the addition, where the tensile strength was 20.5 Nm∙g−1. The results of this research are used for the assessment of nanocellulose as a natural compatible additive to enhance the strength properties of cellulose-based materials. [ABSTRACT FROM AUTHOR]

Coffee production generates large volumes of residue, reaching 32 million tons per year in Brazil alone. This study aimed to evaluate the parchment of coffee fruit, a residue from the coffee industry, in terms of its chemical composition and potential for kraft pulp production. The parchment was characterized with respect to its carbohydrate, lignin, extractive, and mineral contents. The substance was submitted to the kraft pulping process, targeting a kappa number of 25. The main findings of this study are the following: glycans (38.5%), xylans (21.6%), and lignin (27.1%) were the main components of the raw material, the extractive content was 4.5%, quite similar to those found for hardwood species used for pulp production, and the pulping yield was 42.6%. The lignins from the residual were extracted and characterized by their chemical composition, obtained by elemental and pyrolysis–gas-chromatography–mass–spectrometry (Py-GC/MS) analyses. Py-GC/MS analysis from the decomposition of lignin provided the identification of 26 compounds, categorized into six different groups-acids, aldehydes, amines, furans, ketones, and aromatics. Based on chemical biomass characteristics, the pulping performance was similar to those observed for softwood raw materials, with similar pulp bleachability. These results indicate that the evaluated waste biomass has a good potential for use in pulp production. [ABSTRACT FROM AUTHOR]

Hemicellulose-rich pulp raw materials are avoided in the production of man-made cellulosic textile fibres due to hemicellulose reactivity with the currently used industrial solvent systems. Incorporation of hemicelluloses in regenerated fibres could, however, increase the share of used wood biomass and thus improve the environmental footprint of regenerated fibre products. Superbase ionic liquids have shown potential in dissolving and regenerating all the major wood polymers i.e. cellulose, hemicellulose and lignin into regenerated products. In this work, regenerated fibres were spun from hemicellulose-rich softwood and eucalyptus paper-grade pulps and eucalyptus dissolving pulp using a superbase ionic liquid [mTBNH][OAc]. Before dissolution and spinning, intrinsic viscosities of the paper-grade pulps were adjusted either enzymatically or by using a mild acid-treatment to improve dope rheology for dry-jet wet spinning. In fibre spinning, hemicellulose was found to regenerate in high yield and the obtained regenerated fibres had high dry tenacities (5.3 to 15 cN/dtex). The best mechanical properties were measured from fibres with high hemicellulose content (17.3% (w/w)). Pulp pretreatment was found to be critical for achieving good mechanical properties. Acid-pretreatment, which modified both cellulose and hemicellulose, yielded regenerated fibres with better mechanical properties compared to an enzyme-pretreatment which did not alter the hemicellulose structure. Removal of hemicellulose substituents and hydrolysis of hemicellulose backbone in acid-pretreatment may be the key to improved mechanical properties in hemicellulose-containing regenerated fibres. Enzymatic peeling and imaging with a xylan-specific monoclonal antibody (CCRC-M138) suggest that hemicelluloses were enriched to the outermost layers of the regenerated fibres. [ABSTRACT FROM AUTHOR]

ABSTRACT: Kraft pulp (KP), an intermediate product obtained when wood chips are converted to paper, contains highly digestible fiber. This study evaluated the effect of KP inclusion in calf starters on growth performance, health, and plasma glucagon-like peptide 2 (GLP-2) concentration in calves. Twenty-five Holstein heifer calves were raised on a high plane of nutrition program using milk replacer containing 29% crude protein and 18% fat until 49 d after birth, and were fed calf starters containing KP at 0 (CON; n = 14) or 12% (KPS; n = 11) on a dry matter basis. All calves were fed the treatment calf starters and timothy hay ad libitum. Blood was collected at 4, 14, 21, 35, 49, 70, and 91 d after birth. Dry matter intake (DMI) of milk replacer and hay was not affected by treatment, whereas calf starter DMI was lower for KPS (0.93 kg/d) than for CON (1.03 kg/d). Higher neutral detergent fiber (NDF) content in KPS (31.7%) than in the CON starter (22.1%) resulted in higher NDF intake for KPS (0.55 kg/d) than for CON (0.47 kg/d). However, the consumption of starch was lower for KPS (0.29 kg/d) than for CON (0.33 kg/d). Despite the lower starter intake for KPS, body weight and average daily gain did not differ between treatments. No significant difference was observed in the plasma concentrations of metabolites, except for β-hydroxybutyrate (BHB); BHB concentration was lower for KPS (216 μmol/L) than for CON (257 μmol/L). The area under the curve for plasma GLP-2 concentration was higher for KPS (54.1 ng/mL × d) than for CON (36.0 ng/mL × d). Additionally, the fecal score postweaning (1.19 and 1.48 for KPS and CON, respectively) and the number of days that calves developed diarrhea throughout the experimental period (2.50 d and 8.10 d for KPS and CON, respectively) were lower for KPS than for CON. These results indicate that feeding KP reduces the severity and frequency of diarrhea without adversely affecting growth performance. This could be attributed to the increased plasma GLP-2 concentration induced by higher NDF intake.

A study was carried out to observe how active alkali and sulfidity loading affect the kraft pulp characteristics of sweet sorghum bagasse (SSB). SSB pulp was obtained from the kraft pulping with a variation of active alkali (17, 19, and 22%) and sulfidity loading percentage (20, 22, and 24%). The chemical functional group and composition, morphological properties, crystallinity, and pyrolysis product of the resulting pulp were characterized. Based on Fourier transform infrared characterization, SSB pulp demonstrated a peak absorption showing the existence of cellulose, lignin, and hemicellulose. The fibril was found clearly in the pulp fibers of SSB. The crystallinity of treated SSB was higher than that of untreated samples. The Gaussian function gave more accuracy for crystallinity determination (indicated by an R2 value that was relatively higher than the Lorentzian function). It is consistent with Raman spectra in this study, which showed a specific band at 370–380 and ~ 1090 cm−1 from cellulose. The higher carbohydrate content of SSB pulp showed that the delignification process using kraft pulping with a variation of alkali active and sulfidity loading could be an alternative method to cellulose recovery for cellulose-derived products. [ABSTRACT FROM AUTHOR]

Screening of pulp can be expressed as a process where solid contaminants are removed from a pulp slurry without an excessive loss of fibres of acceptable quality. The impurities originate from the feedstock, or they are generated during the transport, handling, storage, or pulping process. The most typical impurities include bark, fibre bundles or shives, knots, plastic, rubber, and sand. Moreover, there are also other objectives for screening, such as the improvement of the pulp quality, savings in bleaching chemical consumption, and protection of process equipment. In industrial applications, pulp screening is typically carried out with more than one screen for a more beneficial screening result. The pulp screening equipment can be divided into different types by the separation technique employed, such as atmospheric or pressurized screens, centrifugal screens, vibrating screens, etc. In addition, there are other types of related equipment that are common in the pulp screening process, such as knotters, refiners, and hydrocyclones. The main objective of this review is to discuss the advantages and disadvantages of modern screening equipment as well as introduce contemporary screening strategies for chemical pulp mills. [ABSTRACT FROM AUTHOR]

Itaconic acid (IA) is a value-added chemical currently produced by Aspergillus terreus from edible glucose and starch but not from inedible lignocellulosic biomass owing to the high sensitivity to fermentation inhibitors present in the hydrolysate of lignocellulosic biomass. To produce IA from lignocellulosic biomass, a gram-positive bacterium, Corynebacterium glutamicum, with a high tolerance to fermentation inhibitors was metabolically engineered to express a fusion protein composed of cis -aconitate decarboxylase from A. terreus responsible for IA formation from cis -aconitate and a maltose-binding protein (malE) from Escherichia coli. The codon-optimized cadA _ malE gene was expressed in C. glutamicum ATCC 13032, and the resulting recombinant strain produced IA from glucose. IA concentration increased 4.7-fold by the deletion of the ldh gene encoding lactate dehydrogenase. With the Δ ldh strain HKC2029, an 18-fold higher IA production was observed from enzymatic hydrolysate of kraft pulp as a model lignocellulosic biomass than from glucose (6.15 and 0.34 g/L, respectively). The enzymatic hydrolysate of kraft pulp contained various potential fermentation inhibitors involved in furan aldehydes, benzaldehydes, benzoic acids, cinnamic acid derivatives, and aliphatic acid. Whereas cinnamic acid derivatives severely inhibited IA production, furan aldehydes, benzoic acids, and aliphatic acid improved IA production at low concentrations. The present study suggests that lignocellulosic hydrolysate contains various potential fermentation inhibitors; however, some of them can serve as enhancers for microbial fermentation likely due to the changing of redox balance in the cell. [Display omitted] • Enzymatic hydrolysate of kraft pulp was used as a model lignocellulosic feedstock. • Kraft pulp hydrolysate enhanced itaconic acid (IA) production by recombinant C. glutamicum. • Some contaminants in kraft pulp hydrolysate improved IA production by recombinant C. glutamicum. [ABSTRACT FROM AUTHOR]

Kraft pulp (KP), an intermediate product obtained when wood chips are converted to paper, contains highly digestible fiber. This study evaluated the effect of KP inclusion in calf starters on growth performance, health, and plasma glucagon-like peptide 2 (GLP-2) concentration in calves. Twenty-five Holstein heifer calves were raised on a high plane of nutrition program using milk replacer containing 29% crude protein and 18% fat until 49 d after birth, and were fed calf starters containing KP at 0 (CON; n = 14) or 12% (KPS; n = 11) on a dry matter basis. All calves were fed the treatment calf starters and timothy hay ad libitum. Blood was collected at 4, 14, 21, 35, 49, 70, and 91 d after birth. Dry matter intake (DMI) of milk replacer and hay was not affected by treatment, whereas calf starter DMI was lower for KPS (0.93 kg/d) than for CON (1.03 kg/d). Higher neutral detergent fiber (NDF) content in KPS (31.7%) than in the CON starter (22.1%) resulted in higher NDF intake for KPS (0.55 kg/d) than for CON (0.47 kg/d). However, the consumption of starch was lower for KPS (0.29 kg/d) than for CON (0.33 kg/d). Despite the lower starter intake for KPS, body weight and average daily gain did not differ between treatments. No significant difference was observed in the plasma concentrations of metabolites, except for β-hydroxybutyrate (BHB); BHB concentration was lower for KPS (216 μmol/L) than for CON (257 μmol/L). The area under the curve for plasma GLP-2 concentration was higher for KPS (54.1 ng/mL × d) than for CON (36.0 ng/mL × d). Additionally, the fecal score postweaning (1.19 and 1.48 for KPS and CON, respectively) and the number of days that calves developed diarrhea throughout the experimental period (2.50 d and 8.10 d for KPS and CON, respectively) were lower for KPS than for CON. These results indicate that feeding KP reduces the severity and frequency of diarrhea without adversely affecting growth performance. This could be attributed to the increased plasma GLP-2 concentration induced by higher NDF intake. [ABSTRACT FROM AUTHOR]

Approaches to obtain nanocellulose have been extensively suggested, and among the most competitive methodologies includes mechanical defibrillation, which results in a nanocellulose gel suspension that can be used in a variety of applications. However, standard procedures results in inhomogeneous fibre sizes due to its physical approach. Pre-treatments have been suggested, such as enzymes, but their cost is a disadvantage. In this work, we suggest the use of cryoslash for bleach kraft pulp using a simple methodology of embedding the dry kraft pulp in distilled water following by freezing at −80 °C, which was slashed using a common blender and submitted to an ultra-fine friction grinder. Samples were studied at various grinding steps 5, 15, 30, 60 and 120. Overall, the energy difference required to defibrillate with cryoslash was ∼3.26 kWh/kg at 30 steps and ∼6 at 120 steps, which was similar to enzymatic pre-treatment with nanofibrils significantly smaller. Cryoslash presented a unique C–H in plane structure from nanocellulose, related to a decrease in average size of fibrils, while crystallinity and thermal properties of nanocellulose remained stable at 60 steps, but mechanical properties increased until 120 steps along with the transmittance values related to the energy consumption curve. [ABSTRACT FROM AUTHOR]

Oxidation of kraft pulp using hydrogen peroxide under mild acidic conditions can be applied in order to obtain new functionality of the fibres, in the form of carbonyl groups. The hydrogen peroxide concentration must, however, be higher than consumed by the oxidation reactions meaning that the liquid must be recirculated to fully utilize the hydrogen peroxide. This paper investigates the consequences of recirculation of the oxidation liquor. It was found that recirculation results in an accumulation of ions of transition metals (copper, iron and manganese) in the oxidation liquor. The transition metal ions are known for catalytic decomposition of hydrogen peroxide, producing radicals which may react with carbohydrates, forming carbonyl groups as well as causing carbohydrate degradation. This was confirmed through the recirculation of oxidation liquor as well as through controlled addition of transition metals. At high transition metal ion concentration the reactions were fast and a severe degradation of carbohydrates was observed, accompanied by a rapid hydrogen peroxide consumption. The consequence of this, in an industrial context, is that the concentration of metal ions must be carefully controlled in order to add functionality to the cellulose without causing excessive degradation of carbohydrates or consumption of hydrogen peroxide. [ABSTRACT FROM AUTHOR]

Although wood is the main source for pulp and paper industry in Brazil, other renewable non-wood fibers could be key alternatives for papermaking. Thus, this study aimed to evaluate the properties of handsheets produced from a mixture of totora (Schoenoplectus californicus) (C.A. Mey.) and Eucalyptus spp. (eucalyptus) fibers. The pulps were refined in laboratory dybeater "PFI type," varying the number of revolutions, in order to obtain refining curves in the range of 15° to 60° SR. The optical, physical, and mechanical properties of the papers produced were evaluated. The addition of totora fibers influenced refining process and paper properties. Moreover, the handsheets produced with the highest content of totora fibers showed low mechanical resistance. Totora is not suitable to be used as a single source of fibers, especially when good mechanical performance is required. However, when the fibers were mixed with eucalyptus, the mixture achieved reasonable resistance. Furthermore, higher opacity was obtained by the addition of totora (≥97%), which is interesting for the printing and writing segment. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing is a useful technique that allows the creation of objects with complex structures by deposition of successive layers of material. These materials are often from fossil origin. However, efforts are being made to produce environmentally friendly materials for 3D printing. The addition of lignocellulosic fibres to a polymer matrix is one of the alternatives to replace, for instance, glass fibres in composites as reinforcing materials. The fields of biocomposites and 3D printing open innovative application areas for pulp fibres from the pulp and paper industry. In this work, biocomposites of poly(lactic acid) (PLA), poly(hydroxyalkanoate) (PHA) and kraft pulp fibres were prepared in order to find a suitable formulation for filaments for 3D printing. The effect of two different types of kraft fibres (bleached (B) and unbleached (U)) and of PHA on the mechanical and thermal properties of the biocomposites was assessed. The addition of 30% kraft fibres to PLA resulted in an increase of the tensile modulus from 3074 to ∼4800 MPa. In the case of biocomposites containing PHA (50% PLA/20% PHA/30% kraft) the increase in modulus was more moderate (PLA+PHA+U: 3838 MPa, and PLA+PHA+B: 3312 MPa). The tensile strength of PLA (66 MPa) increased to 77 MPa in PLA+kraft biocomposites, while a reduction in strength was observed for PLA+PHA+U (43 MPa) and PLA+PHA+B (32 MPa). Filaments prepared with PLA, PHA and bleached and unbleached pulp fibres showed similar printability of complex geometries, demonstrating that unbleached pulp fibres could also be utilized in the preparation of biocomposites with good mechanical performance and 3D printing properties.

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The residual lignin content of unbleached maritime pine (Pinus pinaster Aiton) Kraft pulps was assessed by analytical pyrolysis (Py-lignin) and the results were compared to the Klason lignin content and kappa number. Thirty samples, each from an individual tree, were delignified under identical conditions. The residual lignin content of the pulps varied widely as assessed by Py-lignin (5.9%–9.2%), Klason (8.2–15.1), and kappa number (59–112). Despite a systematic difference between Py-lignin and Klason, they were strongly correlated (R2 = 0.90). The H/G ratio of the residual pulp lignin ranged from 0.145 to 0.195, with a mean of 0.165, which is more than two times the average H/G ratio of Maritime pine wood lignin (0.064). The results show that Kraft pulping, which selectively degrades lignin with more labile inter-unit links, changed the pattern of pyrolysis products of pulp lignin considerably and, consequently, its structure. This pattern shows an enrichment in H-lignin-derived products, namely phenol, p-cresol, and m-cresol, and in some G-lignin-derived products such as guaiacol and 4-mthylguaiacol, and a decrease in coniferylaldehyde, homovanillin, and eugenol. Principal component analysis (PCA) of the G- and H-lignin-derived pyrolysis products shows that pulps are distributed along PC 1 based on their residual lignin content. The loadings plot shows that this separation is mainly due to a small number of G-lignin products, including 4-methyl guaiacol, 4-vinyl guaiacol, isoeugenol (trans), and guaiacol, which are more abundant in pulps with higher residual lignin content. The obtained results show that analytical pyrolysis is an appropriate method for quantifying the residual lignin content and H/G ratio of unbleached Kraft pulps and provide information regarding how lignin is degraded during the pulping process. [ABSTRACT FROM AUTHOR]

Xylanases can boost pulp bleachability in Elemental Chlorine Free (ECF) processes, but their industrial implementation for producing bleached kraft pulps is not straightforward. It requires enzymes to be active and stable at the extreme conditions of alkalinity and high temperature typical of this industrial process; most commercial enzymes are unable to withstand these conditions. In this work, a novel highly thermo and alkaline-tolerant xylanase from Pseudothermotoga thermarum was overproduced in E. coli and tested as a bleaching booster of hardwood kraft pulps to save chlorine dioxide (ClO2) during ECF bleaching. The extremozyme-stage (EXZ) was carried out at 90 °C and pH 10.5 and optimised at lab scale on an industrial oxygen-delignified eucalyptus pulp, enabling us to save 15% ClO2 to reach the mill brightness, and with no detrimental effect on paper properties. Then, the EXZ-assisted bleaching sequence was validated at pilot scale under industrial conditions, achieving 25% ClO2 savings and reducing the generation of organochlorinated compounds (AOX) by 18%, while maintaining pulp quality and papermaking properties. Technology reproducibility was confirmed with another industrial kraft pulp from a mix of hardwoods. The new enzymatic technology constitutes a realistic step towards environmentally friendly production of kraft pulps through industrial integration of biotechnology. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing is a useful technique that allows the creation of objects with complex structures by deposition of successive layers of material. These materials are often from fossil origin. However, efforts are being made to produce environmentally friendly materials for 3D printing. The addition of lignocellulosic fibres to a polymer matrix is one of the alternatives to replace, for instance, glass fibres in composites as reinforcing materials. The fields of biocomposites and 3D printing open innovative application areas for pulp fibres from the pulp and paper industry. In this work, biocomposites of poly(lactic acid) (PLA), poly(hydroxyalkanoate) (PHA) and kraft pulp fibres were prepared in order to find a suitable formulation for filaments for 3D printing. The effect of two different types of kraft fibres (bleached (B) and unbleached (U)) and of PHA on the mechanical and thermal properties of the biocomposites was assessed. The addition of 30% kraft fibres to PLA resulted in an increase of the tensile modulus from 3074 to ~4800 MPa. In the case of biocomposites containing PHA (50% PLA/20% PHA/30% kraft) the increase in modulus was more moderate (PLA + PHA + U: 3838 MPa, and PLA + PHA + B: 3312 MPa). The tensile strength of PLA (66 MPa) increased to 77 MPa in PLA + kraft biocomposites, while a reduction in strength was observed for PLA + PHA + U (43 MPa) and PLA + PHA + B (32 MPa). Filaments prepared with PLA, PHA and bleached and unbleached pulp fibres showed similar printability of complex geometries, demonstrating that unbleached pulp fibres could also be utilized in the preparation of biocomposites with good mechanical performance and 3D printing properties. [ABSTRACT FROM AUTHOR]

Tissue paper was the only paper grade whose consumption increased during 2020 in Europe. In a highly competitive context, this work explores a strategy based on bisacrylamide cross-linkers and poly(vinyl alcohol) (PVA), seeking to enhance the water uptake of pulps for tissue paper and the key properties of the resulting tissue sheets: water absorption capacity, capillarity, softness, porosity, and strength. For that, α-cellulose from cotton and a kraft hardwood pulp, in parallel, were reacted with N,N'-methylenebisacrylamide, both in the absence and in the presence of PVA. The water desorption rate of the modified polymers was monitored. Pulp blends were then mixed with a conventional softwood pulp (30%) to prepare laboratory tissue paper sheets (20 g m–2). For cotton cellulose, cross-linking with PVA more than doubled the water uptake, up to 7.3 g/g. A significant enhancement was also obtained in the case of pulps, up to 9.6 g/g, and in the case of paper, to 11.9 g/g. This improvement was consistent with a drastic increase in porosity, and it was not detrimental to paper strength. [ABSTRACT FROM AUTHOR]

The objective of this study is to gain further insight into the compositional and physical changes of kraft pulp caused by oxidation with hydrogen peroxide under acidic conditions. A softwood kraft pulp has been subjected to varying degrees of oxidation. Changes in the composition, as well as resulting physical properties of laboratory sheets were investigated. Findings indicated that the oxidation resulted in an increased carbonyl group content, a decrease in intrinsic viscosity and a change in hemicellulose composition. The oxidized pulps were found to have a reduced water retention value and a slightly reduced tensile strength (4–11 % at the investigated conditions). However, a substantial increase in wet web tensile strength (6–23 %) and wet tensile strength (134–242 %) of the sheets was obtained. The sheets could easily be repulped and an increased wet strength maintained to a large extent, even after recycling of the sheets. [ABSTRACT FROM AUTHOR]

Cellulose nanofibrils (CNF) isolation based on a catalyst-free maleic anhydride esterification has proven to be effective, however, the effects of pulp hornification on CNF isolation by this strategy have yet to be explored, which could present significant impacts for CNF isolation. Herein, dried northern bleached softwood Kraft pulp (D-NBSK) and never-dried northern bleached softwood Kraft pulp (ND-NBSK) were selected as the substrates. After esterification with maleic anhydride (MA), the esterified ND-NBSK pulp (E-ND) shows a significantly smaller size and more fragmented structure than the esterified D-NBSK pulp (E-D). Meanwhile, higher degree of esterification can be realized for the never dried pulp as compared to the dried pulp, which is corroborated by the significantly stronger characteristic peaks of C O (1720 cm−1) and -COO− (1575 cm−1) from the FTIR spectra and the higher surface charge content (0.86 ± 0.04 mmol/g vs. 0.55 ± 0.05 mmol/g). A comparison of the characteristics of the resulting CNF similarly demonstrated the negative impact of hornification. Overall, this work indicates that hornification tends to reduce the accessibility of chemical reagents to the pulp, leading to insufficient deconstruction. Such negative impact of hornification should be considered when performing nanocellulose isolation, especially when using pulp as feedstock. [Display omitted] [ABSTRACT FROM AUTHOR]

The world demand for paper has been increased due to the increasing population Therefore, to cop up the limited wood fiber resources introducing raw material in pulp and paper industries is necessary. The aims of this study to evaluate the pulp and paper-making properties of Caesalpinia decapetela based on proximate chemical composition, fiber morphology, pulping, bleaching, and physical test of the final product. The results proximate chemical analysis showed that C. decapetela has holocellulose content of 78.14±0.1 % and lignin content 18.0±0.04 %. Fiber morphology revealed that the fibers were 0.708 mm long, 18.63 μm width, and have 5.1 μm cell wall thicknesses. Kraft pulping of C. decapetale, was performed at different active alkali (5 %, 10 %, 15 %, 20 % and 25 %) and temperature (150, 160 and 170 °C), keeping the sulphidity 25 % constant. The pulp maximum yield 44.1 % was obtained at active alkali content of 15 %, temperature 160 °C, and cooking time 90 minutes. The effect of pulping on fiber morphology was studied using scanning electron microscopy which showed the surface of fiber before pulping was tight, orderly arranged and the texture was relatively hard. After pulping, there was the removal of lignin, hemicellulose, and cellulose. Due to this fiber become soft loosened and contain micro-pores. Pulp produced was bleached, sheet preparation and testing were performed. The prepared paper sheets have a tensile index of 28.19 Nm/gm, burst index of 1.359 kPa m 2 / gm 1.359\hspace{0.1667em}\text{kPa}\hspace{0.1667em}{\text{m}^{2}}/\text{gm} , and tear indices of 4.2 mN m 2 / gm 4.2\hspace{0.1667em}\text{mN}\hspace{0.1667em}{\text{m}^{2}}/\text{gm}. This study concluded C. decapetale can be the new raw material for pulp and paper making industries. However, pilot plant studies are required to check this raw material for the full recommendation of the pulp and paper industries. [ABSTRACT FROM AUTHOR]

In the current work, cellulose nanofibers (CNF) were isolated from unbleached kraft pulps of date palm fruit stalks (DPFS) and date palm rachis (DPR) residues by ultrafine grinding. The isolated CNF were characterized by high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), zeta potential measurement, tensile strength properties, contact angle, as well as oil-proof testing. The CNF were applied as a coating material for cardboard paper sheets made from unbleached kraft DPFS and DPR pulps. The results showed that CNF from DPFS and DPR had close dimensions (4–14 nm in width and several microns in length) but their zeta potential was different (−44.65 eV and −51.46 eV for CNF from DPFS and DPR pulps, respectively), as well as their crystallinity (79.4% and 75.5% for CNF from DPFS and DPR pulps, respectively). CNF films from DPFS had tensile stress and Young's modulus of 113.3 MPa and 3.81 GPa, respectively, while those from DPR had tensile stress and Young's modulus of 71.0 MPa and 2.93 GPa, respectively. Films from DPFS CNF showed lower hydrophilicity than that from DPR, nevertheless excellent oil-proof property was obtained in both kinds of films. Coating of cardboard sheets prepared from unbleached kraft DPFS and DPR pulps with CNF layer of about 7-µm thickness resulted in significant changes in some physical properties of paper sheets, such as decreasing their air permeability, water vapor transmission rate, and water absorption; both kinds of CNF imparted paper sheets good oil-proof properties. CNF coating also imparted paper sheets remarkable wet tensile strength properties. The results showed the feasibility of utilizing date palm wastes in producing CNF films with distinct properties from low-cost unbleached kraft pulp, as well as using these CNF as a multi-functional coating material in papermaking industry. • Cellulose nanofibers (CNF) were isolated from unbleached date palm pulps. • The properties of CNF were dependent on the date palm residue used. • CNF films had excellent oil-proof and good mechanical properties. • CNF were successfully used for coating cardboard sheets. • CNF coating improved wet strength, air, oil, and moisture barrier properties. [ABSTRACT FROM AUTHOR]

Considering the toxicity of the impurities of synthesized anthraquinone, this study clarified new catalytic compounds for kraft cooking with improved carbohydrate yield and delignification and less mutagenicity, which are important for ensuring the safety of paper products in contact with food. The 2-methylanthraquinone contents of teak (Tectona grandis) woods were 0.18–0.21%. Acetone extracts containing 2-methylanthraquinone from Myanmar and Indonesia teak woods as additives improved lignin removal during kraft cooking of eucalyptus wood, which resulted in kappa numbers that were 2.2–6.0 points lower than the absence of additive. Myanmar extracts and 2-methylanthraquinone improved carbohydrate yield in pulps with 1.7–2.2% yield gains. Indonesia extracts contained more deoxylapachol and its isomer than 2-methylanthraquinone. The residual content of 2-methylanthraquinone in the kraft pulp was trace. Although Ames tests showed that the Indonesia and Myanmar extracts were mutagenic to Salmonella typhimurium, 2-methylanthraquinone was not. The kraft pulp obtained with the additives should be safe for food-packaging applications, and the addition of 0.03% 2-methylanthraquinone to kraft cooking saves forest resources and fossil energy in industries requiring increased pulp yield.

Nowadays, the emphasis is on increasing the durability of all products. For this reason, it is also advisable to look into extending the durability of paper products. The main reason for using flax pulp is that flax and cotton pulp are widely used for the production of banknotes due to their higher strength. This paper deals with flax pulp with the addition of nanocellulose, which should further enhance the mechanical properties of the pulp. The tensile strength, breaking length, and tensile energy absorption index were evaluated as the key mechanical properties. At the same time, the effect of the addition of nanocellulose, whether it was added to the pulp mass or applied to the later produced paper as a spray or coating, was tested in comparison to paper without the addition of nanocellulose. The best mechanical properties, i.e., tensile strength, were achieved for the highest addition of 5% of nanocellulose into the pulp, at 24.3 Nm∙g -1 , and for the coating application, at 28.7 Nm∙g -1 , compared to the flax pulp without the addition, where the tensile strength was 20.5 Nm∙g -1 . The results of this research are used for the assessment of nanocellulose as a natural compatible additive to enhance the strength properties of cellulose-based materials.