Bleached Softwood Kraft Research Articles

Preparation of cellulose-based lithium ion battery membrane enhanced with alkali-treated polysulfonamide fibers and cellulose nanofibers

A cellulose-based lithium ion battery (LIB) membrane fabricated with northern bleached softwood kraft pulp (NBSK), alkali-treated polysulfonamide (A-PSA) and cellulose nanofibers (CNF) have been prepared successfully. PSA fibers are firstly treated by alkali for more carboxyl and amino groups on their surface. Then A-PSA@CNF composites are formed by the adsorption of CNF on the surface of A-PSA fibers and found to possess improved electrolyte wettability and mechanical strength properties, as well as better retention and distribution of CNF in the membrane. The cellulose-based membrane is obtained from NBSK fibers and A-PSA@CNF composites via a facile paper-making process. It is found that the NBSK/A-PSA/CNF membrane shows better mechanical strength and narrower pore size distribution, higher electrolyte wettability and thermal stability compared with those of the control, thanks to the excellent properties of A-PSA@CNF composites. The testing LIB cell assembled with the prepared cellulose-based membrane shows high capacitance performance even after 100 charge/discharge cycles. The study puts forward a novel approach to modify PSA fiber with alkali treatment and following CNF adsorption, to improve its electrolyte wettability and mechanical properties during the preparation of cellulose-based separator.

Comparison of wood and non-wood market pulps for tissue paper application

A comparison among ten market pulps at a laboratory scale using uncreped tissue handsheets was performed to study the performance of wood and non-wood pulps for tissue manufacturing, evaluate what fiber features are desired for a specific tissue property, and determine how non-wood pulps can be used to replace or complement wood pulps in tissue products. A characterization of the fiber morphology and handsheet properties (softness, water absorbency, and strength) was performed at different mechanical refining levels. The results showed that the fiber morphology had a major impact on tissue properties. Market pulps with a combination of long fibers, high coarseness, and low fines content can provide superior bulk and water absorbency. Short fibers with thin cell walls and low fines content can impart superior softness. Bleached bamboo soda pulp can replace hardwood and softwood pulps to provide an excellent combination of water absorbency and strength. Bleached bamboo soda pulp can also replace Northern bleached softwood kraft (NBSK) pulp to impart strength without sacrificing softness. Bleached and semi-bleached wheat straw soda pulps presented a similar combination of softness and strength as Southern bleached hardwood kraft (SBHK) pulp. The wheat straw pulps can be used to replace deinked pulp (DIP) pulp to impart intermediate levels of water absorbency and strength.

Carbon dioxide capture from pulp mill using 2-amino-2-methyl-1-propanol and monoethanolamine blend: Techno-economic assessment of advanced process configuration

This project study involves the techno-economic assessment of two new advanced configurations for amine-based carbon dioxide capture from a pulp mill. The newly proposed advanced configurations include advanced rich amine four split (ARA4S), and advanced rich amine three split with desorber inter-heating (ARA3S-DI) which is aimed at reducing carbon capture cost and carbon emissions. The rate-based model in ProMax® 4.0 was used for the simulation study while the flue gas was provided by a 365,000 air dry tonne of pulp (ADt Pulp) per annum pulp mill in British Columbia, Canada. Comparative analysis revealed that the Capture Cost (US$/tCO2 and US$/ADt Pulp) of the 5 kmol/m3 MEA system was lowest for the conventional configuration, while for the 2 kmol/m3 AMP-3 kmol/m3 MEA blend it was lowest for the advanced rich amine 3-split with desorber inter-heating configuration. In addition, the Capture Costs of the MEA solution with a conventional configuration system is 8.7% higher than the AMP-MEA blend with advanced rich amine three split with desorber inter-heating configuration. Sensitivity analysis revealed that the combined effect of a carbon tax (US$ 40/tCO2), CO2 sales price (US$ 40/tCO2) and advanced configuration only led to a slight increase (2.6% for MEA and 2.1% for AMP-MEA blend) in the price of the northern bleached softwood kraft pulp. With an even better-performing solvent system and process configuration, the price of NBSK pulp may not be affected given the indicated CO2 tax and CO2 price regime.

Effect of cellulase family and structure on modification of wood fibres at high consistency

Enzymatic modification of bleached softwood kraft fibres for improved fibre reactivity was studied at high (20% w/w) and low (1% w/w) dry matter content. The role of enzyme family and structure in fibre modification was assessed using endoglucanases from three structurally different glycoside hydrolase (GH) families (5, 7 and 45) with and without a carbohydrate binding module (CBM). Based on the amount of dissolved sugars, enzyme action at high consistency was about sixfold higher compared to a fibre treatment at low consistency. The GH45 endoglucanase was found to be most specific in acting on pulp cellulose whereas the family 5 and 7 endoglucanases had activity also on pulp hemicelluloses. The GH45 endoglucanase was found to be most efficient in reducing molecular weight and viscosity of the pulp. In addition, treatment with the GH45 endoglucanase resulted in the highest micropore volume in fibres and thus an increase in cellulose accessibility. The increased accessibility could be seen as decreased dissolution time in cupriethylenediamine using recently developed analytical techniques: viscometric analysis and microscopic video analysis. At high consistency, CBM was not promoting enzyme action, although CBMs are known to be beneficial at low dry matter conditions.Graphical abstract

Carbon Fibers from Lignin-Cellulose Precursors: Effect of Stabilization Conditions

There is an increasing demand for lightweight composites reinforced with carbon fibers (CFs). Due to its high availability and carbon content, kraft lignin has gained attention as a potential low-cost CF precursor. CFs with promising properties can be made from flexible dry-jet wet spun precursor fibers (PFs) from blends (70:30) of softwood kraft lignin and fully bleached softwood kraft pulp. This study focused on reducing the stabilization time, which is critical in CF manufacturing. The impact of stabilization conditions on chemical structure, yield, and mechanical properties was investigated. It was possible to reduce the oxidative stabilization time of the PFs from about 16 h to less than 2 h, or even omitting the stabilization step, without fusion of fibers. The main reactions involved in the stabilization stage were dehydration and oxidation. The results suggest that the isothermal stabilization at 250 °C override the importance of having a slow heating rate. For CFs with a commercial diameter, stab...

X-Ray Nanotomography of Individual Pulp Fibre Bonds Reveals the Effect of Wall Thickness on Contact Area

Fibre bonds play an essential role in various properties of paper. Much research has focused on their strength, but the determination of the actual contact area also provides a challenge. Many of the research methods rely on optical tools, which are restricted by the wavelength of light that is utilised. Novel X-ray computed tomography devices utilise X-rays in studying the inner structure of materials, and surpass the optical methods in terms of resolution, allowing detection of even smaller details and variations in distance between the fibres in the bond intersection area. X-ray nanotomography was used to image 26 individual cellulose fibre bonds made of springwood and summerwood fibres of refined bleached softwood kraft pulp. Various dimensional properties of the bonds were measured, most importantly the relative contact area (apparent contact area/intersection area), whose values showed wide variation from 6.4 to 85% with an average of 57.7%. Although the summerwood bonds had a somewhat smaller intersection and contact area than springwood bonds, there were no significant differences in the relative contact area between the bond types. This suggests that the effect of relative and absolute contact area on the strength differences between bond types seems to be minor.

Prospects for the preparation of paper money from cotton fibers and bleached softwood kraft pulp fibers with nanofibrillated cellulose

Paper money passes through various environments during its life span, causing its physical, chemical, and optical properties to change. More than 90% of paper money worldwide is composed of natural cotton fiber. The present study examined the properties of paper money made of bleached softwood kraft fibers or its blends with cotton fibers, where nanofibrilled cellulose was employed as a strengthening agent. Nano-cellulose was added at 4 levels: 0, 0.3, 0.6, and 0.9%. Handsheets with a basis weight of 90 g·m-1 were made by mixing the pulp furnish with nano-cellulose in the identified percentages, and the physical and mechanical properties of the handsheets were tested. By increasing the amount of nano-cellulose up to 0.9% in cotton pulp, the tensile strength, bursting resistance, tear resistance, and resistance to folding endurance were increased by 33, 33.5, 6.6, and 63.2%, respectively, compared with the control sample. The addition of nano-cellulose up to 0.9% in cotton pulp increased the surface smoothness by up to 13.5% compared with the control sample, and porosity and water absorbance decreased by 16.6 and 4%, respectively, in comparison with the control sample. By increasing nano-cellulose up to 0.9% in cotton pulp, the opacity, brightness, and whiteness were decreased by 0.1, 1, and 4%, respectively. The SEM results indicated that the increased nano-cellulose percentage led to decreased porosity.

Influence of pulp type on the three-dimensional thermomechanical convertibility of paperboard

This study examines the effect of pulp type on the formability and elongation of paperboard, which are of key importance when producing 3D packages. Material performance was studied with a press-forming machine using laboratory handsheets as substrates. The handsheets were prepared from bleached softwood and hardwood kraft pulps, chemi-thermomechanical pulp, recycled newsprint, and mixtures of birch kraft and other pulps. The effect of microfibrillated cellulose (MFC) on substrate properties and material formability was also investigated. The 3D elongation of MFC-free handsheets varied between 1.2 and 5.5%. Depending on the pulp type and sheet composition, three essential sheet properties were recognized. These properties were bulk, elastic modulus and bending stiffness, the first two of which affect material bending stiffness. Sheets made from softwood fibers were superior to other samples, but their low bending stiffness resulted in distortion of formed trays. A partial replacement of birch kraft with recycled newsprint did not lead to a loss of sheet extensibility, which suggests that the interactions between the converting tools and the substrate have a great effect on material convertibility. Scanning electron micrographs showed that the pulp type affects the mechanism behind fracture initiation. The ability of MFC to increase extensibility was limited to mechanical pulps, indicating the important role of the main pulp component in defining tensile properties.Graphical abstract

Highly Dispersible Cellulose Nanofibrils Produced via Mechanical Pretreatment and TEMPO-mediated Oxidation

Cellulose nanofibrils (CNFs) can prepare flexible nanomaterials with its large aspect ratio. Due to the supramolecular, cellulose fibers are difficultly dissociated to CNFs. In order to destroy this supramolecular structure and prepare high dispersible CNFs, the mechanical and chemical treatments are required. This study examined the effects of mechanical pretreatment and TEMPO-oxidation on the properties of CNFs preparing from bleached softwood kraft pulp. The total yield of TEMPO-oxidized cellulose nanofibrils (TOCNFs) reached 85 %. The morphology, carboxyl group content, crystallinity, surface charge, self-assembling properties, and optical transmittance of the corresponding TOCNFs suspension were investigated. The transmittance of TOCNFs suspension was 95.1 % at 600 nm wavelength and its corresponding ζ- potential was -61.3 mV, indicated that the strong electrostatic repulsion between TOCNFs was the most significant factor on the highly transparent TOCNFs suspension in water. Furthermore, the mostly negative charged TOCNFs obtained by freeze drying assembled into the finest and most uniform networked structure. Such highly transparent, functionalized, selfassembled cellulose nanofibrils are favorable in transparent films, flexible displays and electrochemistry materials.

Preparation and Characterization of Acetylated Nanocrystalline Cellulose-reinforced Polylactide Highly Regular Porous Films

Nanocrystalline cellulose was prepared from bleached softwood kraft pulp using acid hydrolysis. Acetylated nanocellulose (AcNCC) and polylactic acid (PLA) were mixed together at different proportions under certain humidity conditions using a miscible method to prepare highly regular porous AcNCC/PLA composite films. The composites were characterized using scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The PLA/Ac-NCC-4 showed a uniform pore diameter distribution with diameter of 1.0 μm to 5.0 μm. The mechanical properties and thermal stability of the PLA composites were improved with the addition of AcNCC. The pore structure was regular and well distributed. When the AcNCC loading was 4%, the tensile strength and Young’s modulus of the composites were 2.07 and 2.41 times higher than that of the pure PLA, respectively. The composites also exhibited high visible light transmission.

Utilization of Cellulose Micro/Nanofibrils as Paper Additive for the Manufacturing of Security Paper

Effects of cellulose micro/nanofibrils were investigated relative to the strength and drainability of security paper made from cotton lint mixed pulp. Six types of cellulose micro/nanofibrils were made from bleached softwood kraft pulp (SwBKP) and bleached hardwood kraft pulp (HwBKP) using refining and micro-grinding processes, respectively. After their main properties were measured, handsheets were produced by adding micro/nanofibrils into a cotton pulp furnish, and the physical properties of the sheets were measured. The cotton pulp furnish drainage rate was also analyzed with respect to the dosage and the fibrillation degree of the cellulose micro/ nanofibrils. The cellulose micro/nanofibrils made from SwBKP resulted in higher viscosity, lower particle size, and higher zeta-potential than those made from HwBKP. The nanofibrils made from SwBKP were the most effective for enhancing the tensile strength, folding endurance, and sheet density of the security papers made from cotton lint mixed pulp. However, the cellulose micro/nanofibrils made from SwBKP could be limited as a paper additive in papermaking due to its high drainage resistance. Because the cellulose micro/nanofibrils made from HwBKP also reduced the drainage rate, the dosage and the fibrillation degree should be controlled by simultaneously considering the paper strength and drainage.

Fiber Evolution during Alkaline Treatment and Its Impact on Handsheet Properties

To understand the swelling effects of alkaline treatment on the morphological properties of fibers and physical properties of handsheets, bleached softwood kraft pulp was treated with NaOH at different concentrations. The results showed that the fiber swelling increased, but the shrinkage and elongation of the paper at a NaOH concentration of 6% or higher did not improve. Dissolution of amorphous material occurred during the treatment together with peeling reactions. The fiber length and shape factor decreased and the fines content increased with an increasing alkali concentration. The cellulose crystallinity decreased with an increasing NaOH concentration. This was confirmed by X-ray diffractometry, which also showed that some cellulose I was converted to cellulose II, especially at higher NaOH concentrations (> 9%). The fiber curl and kink indices increased and the handsheet density decreased with an increasing NaOH concentration. However, the tensile index decreased more steeply than the density with an increasing NaOH concentration, possibly because of the lower number and strength of the interfiber bonds, increased kinks, and reduced fiber strength and length. The handsheet extensibility first increased and subsequently decreased as the NaOH concentration increased, which indicated that well-controlled NaOH treatment could be used to improve the extensibility of paper.

The relationship between shrinkage and elongation of bleached softwood kraft pulp sheets

AbstractThe relationship between shrinkage and elongation of hand sheets was examined. The results show that the same dimensional contraction brought about by shrinkage can be strained out in tensile testing. However, percentage-wise the elongation is greater than the shrinkage due to different reference points, and the difference increases strongly at higher shrinkage levels. Elongation of paper can be explained mainly by two factors: the shrinkage and the net elongation of paper. Here shrinkage refers to all kinds of in-plane contraction of the fiber network (drying shrinkage, in-plane-compaction and creping). The novel concept ‘net elongation’ was proposed in order to separate the effect of shrinkage from the total elongation of paper. Net elongation is the elongation of corresponding unshrunken paper dried under restraint. Sheets with high elongation were prepared from bleached softwood kraft pulp and the effects of shrinkage on elongation, strength and stiffness of the paper were investigated. Mechanical treatment methods of pulp fibers and chemical strength additives were applied in order to maximize the strength and elongation. In-plane compaction and creping were used to further boost shrinkage of the high basis weight (100 g/m2) sheets up to 160 percent. Experimental elongation data confirmed the proposed theoretical relationships.

Bar force measurement in low consistency refining: the effect of plate pattern

Abstract The effect of plate pattern on forces applied to pulp fibers by refiner bars in low consistency refining is investigated in an AIKAWA 16-inch single-disc refiner. These forces are measured using a custom-built piezoelectric sensor. Trials are conducted using SPF softwood thermomechanical pulp, northern bleached softwood kraft pulp, and aspen hardwood thermomechanical pulp at 3.3 to 3.6 % consistency at rotational speeds of 1200 and 1400 rpm. The pulp is sampled at regular intervals, and the length-weighted fiber length, freeness, tear index, and tensile index are measured for each sample. The results show that the plate with higher bar edge length results in lower mean peak normal and shear forces. The mean peak normal and shear forces at the onset of fiber cutting depend on rotational speed, pulp furnish and plate pattern, and these parameters are lower for a plate pattern with higher bar edge length. In addition, the mean coefficient of friction is a function of plate gap, pulp furnish, and plate pattern. The plate having higher bar edge length results in higher mean coefficient of friction.

Indications of the onset of fiber cutting in low consistency refining using a refiner force sensor: The effect of pulp furnish

Abstract Detection of the onset of fiber cutting is beneficial in low consistency refining as it may prevent reduction of average fiber length, optimize fiber quality improvements by operating at gaps just wider than the critical gap, avoid decreasing the strength properties of paper, and increase energy efficiency. The objective of this study is to understand the effect of pulp furnish on measured bar forces and, more specifically, on the detection of fiber cutting. Bar forces, i. e. forces applied to pulp fibers by the refiner bars, are measured with a custom-designed piezoelectric force sensor. Trials were conducted with an AIKAWA 16-in. single-disc refiner using hemlock/balsam softwood thermomechanical pulp, SPF softwood thermomechanical pulp, northern bleached softwood kraft pulp, and aspen hardwood thermomechanical pulp at 3.0 to 3.5 % consistency at rotational speeds of 1200 and 1400 rpm. The power of the time domain signal of the measured forces is introduced as an indicator of the onset of fiber cutting. Our results show that this new fiber cutting metric is a sensitive and reliable metric for determination of fibre cutting for a range of pulp furnishes. The study suggests that the refiner force sensor has potential to be exploited for in-process detection of fiber cutting.

An ultra-lightweight recyclable carbon aerogel from bleached softwood kraft pulp for efficient oil and organic absorption

A carbon aerogel with porous structure was synthesized from bleached softwood kraft pulp (BSKP) via eco-friendly freezing-drying and carbonization steps. The obtained carbon aerogel exhibited a low density of 25.5 mg cm−3, high hydrophobicity with a water contact angle of 139.7° and good compressive properties. When used as an absorbent, the carbon aerogel could absorb 14 to 26 times its own weight in organic solvent and oil. Furthermore, the aerogel could be easily recovered and regenerated through burning, pressure recycling, and squeezing, and a high adsorption efficiency was maintained over a number of cycles. The use of biomass as a raw material, together with the excellent hydrophobicity and recyclability, make this carbon aerogel a suitable adsorbent for a variety of practical separation requirements.

An effective method for determining the retention and distribution of cellulose nanofibrils in paper handsheets by dye labeling

Cellulose nanofibrils (CNF) were prepared by cellulase in conjunction with mechanical disintegration from the bleached softwood kraft pulp and labelled by Congo red dye. The labelled CNF were used to investigate the retention and distribution of CNF in paper handsheets. The retention of the labelled CNF was obtained by measuring the absorbance of white water using an ultraviolet-visible spectrophotometer. The results showed that this method for measuring the retention was rapid, feasible, and sensitive, owing to the high correlation coefficient R2 (0.9993) of the standard curve. The labelled CNF showed even distribution in paper handsheets. The colorimetric values of paper handsheets were explored with a residual ink analyzer.

Clustered Single Cellulosic Fiber Dissolution Kinetics and Mechanisms through Optical Microscopy under Limited Dissolving Conditions

Herein, we describe a new method of assessing the kinetics of dissolution of single fibers by dissolution under limited dissolving conditions. The dissolution is followed by optical microscopy under limited dissolving conditions. Videos of the dissolution were processed in ImageJ to yield kinetics for dissolution, based on the disappearance of pixels associated with intact fibers. Data processing was performed using the Python language, utilizing available scientific libraries. The methods of processing the data include clustering of the single fiber data, identifying clusters associated with different fiber types, producing average dissolution traces and also extraction of practical parameters, such as, time taken to dissolve 25, 50, 75, 95, and 99.5% of the clustered fibers. In addition to these simple parameters, exponential fitting was also performed yielding rate constants for fiber dissolution. Fits for sample and cluster averages were variable, although demonstrating first-order kinetics for dissolution overall. To illustrate this process, two reference pulps (a bleached softwood kraft pulp and a bleached hardwood pre-hydrolysis kraft pulp) and their cellulase-treated versions were analyzed. As expected, differences in the kinetics and dissolution mechanisms between these samples were observed. Our initial interpretations are presented, based on the combined mechanistic observations and single fiber dissolution kinetics for these different samples. While the dissolution mechanisms observed were similar to those published previously, the more direct link of mechanistic information with the kinetics improve our understanding of cell wall structure and pre-treatments, toward improved processability.

Surface Charge Influence on the Phase Separation and Viscosity of Cellulose Nanocrystals.

A series of four cellulose nanocrystal (CNC) suspensions were prepared from bleached softwood kraft pulp using different conditions of sulfuric acid hydrolysis. The CNCs were identical in size (95 nm in length × 5 nm in width) but had different surface charges corresponding to the harshness of the hydrolysis conditions. Consequently, it was possible to isolate the effects of surface charge on the self-assembly and viscosity of the CNC suspensions across surface charges ranging from 0.27%S to 0.89%S. The four suspensions (never-dried, free of added electrolyte) all underwent liquid crystalline phase separation, but the concentration onset for the emergence of the chiral nematic phase shifted to higher values with increasing surface charge. Similarly, suspension viscosity was also influenced by surface charge, with suspensions of lower surface charge CNCs more viscous and tending to gel at lower concentrations. The properties of the suspensions were interpreted in terms of the increase in effective diameter of the nanocrystals due to the surface electrostatic repulsion of the negative sulfate half-esters, as modified by the screening effects of the H+ counterions in the suspensions. The results suggest that there is a threshold surface charge density (∼0.3%S) above which effective volume considerations are dominant across the concentration range relevant to liquid crystalline phase formation. Above this threshold value, phase separation occurs at the same effective volume fraction of CNCs (∼10 vol %), with a corresponding increase in critical concentration due to the decrease in effective diameter that occurs with increasing surface charge. Below or near this threshold value, the formation of end-to-end aggregates may favor gelation and interfere with ordered phase formation.

Coupling of PLA and bleached softwood kraft pulp (BSKP) for enhanced properties of biocomposites

The interest in totally bio-based materials is increasing due to their low carbon footprint and improved properties through intensive research. Polylactide (PLA)-based cellulose fibre compounds are finding their way into various injection-moulded applications. In addition to gain high-performance PLA–cellulose pulp fibre composites, there are also needed for additives such as plasticizers and coupling agents in the compounds. This research presents the use of a renewable material–based combined plasticizer-coupling agent as an additive in PLA bleached softwood kraft pulp (BSKP) composite. An epoxy-modified linseed oil showed capability for cross-linking PLA and cellulose fibre so enabling simultaneously improved strength tensile and impact properties for composite materials when added in amount of below 8% to fibre.