Properties Of Pulp Fibers Research Articles

Effects of Enzyme Mixture and Beating Treatment on the Properties of Pulp Fibers

Effects of Enzyme Mixture and Beating Treatment on the Properties of Pulp Fibers

Quantification of the microdeformation degree of fast-growing poplar wood during prehydrolysis and its relationship with subsequent pulping

Prehydrolysis is a typical pretreatment in dissolving pulp preparation to remove hemicellulose prior to pulping. In this study, we employed the combined severity factor (CSF) as a reaction parameter to control the pretreatment intensity during prehydrolysis of fast-growing poplar wood, and we investigated the influence of the pretreatment intensity on the components and morphology of wood chips. To assess the microstructural changes in the cell wall, we introduced a mathematical model named the microdeformation coefficient (MDC) to quantitatively evaluate the degree of microstructural deformation and verified its validity and reliability under different CSFs. The results indicated that the MDC could precisely describe the significance of the effect of prehydrolysis on microstructural changes in wood chips. Furthermore, the relationship between the MDC and the physicochemical properties of pulp fibers and handsheets was explored. A moderate MDC of approximately 0.0050 is suggested to attain good hemicellulose removal and produce pulp with good properties (accept pulp content = 47.21 %, permanganate numbers = 18.23, degree of polymerization (DP) = 1774.40) after prehydrolysis. Moreover, the produced handsheets exhibited excellent properties (brightness = 29.50 %, fold resistance = 5.11 times, tensile index = 81.43 N mg, and tear index = 6.36 mN·m2/g).

Transverse viscoelastic properties of pulp fibers investigated with an atomic force microscopy method

Changes in moisture content of single pulp fibers have an immense influence on the behavior of paper and paper products. Here, an atomic force microscopy (AFM)-based method is applied to investigate the viscoelastic properties of pulp fibers at varying relative humidity (RH) in the transverse direction. Pulp fibers have not only anisotropic properties, but also a very rough surface due to their hierarchical structure. For this reason, we have developed a specific load schedule for the AFM-based test method to overcome uncertainties and limitations due to surface roughness of the pulp fibers. The evaluation of the experimental data combines contact mechanics and viscoelastic models which consist of springs and dashpots in series or parallel describing elastic and viscous behavior. Here, it will be demonstrated that the so-called Generalized Maxwell (GM) model yields comparable results for single pulp fibers at five different RH values and in water. The moisture changes lead to a decrease in the elastic modulus but increase in the relaxation effects with increasing RH. All the determined parameters for the elastic and viscous behavior exhibit a gradual decrease with increasing RH from 10 to 75% RH. The elastic moduli decrease by a factor of 10 and the viscosities are decreasing by a factor of 10–20. In water, there is an even more pronounced decrease of the elastic moduli by a factor 100, and the viscosities decrease by at least three orders of magnitude compared to 10% RH. This indicates that the mechanical response of pulp fibers in water is significantly different than in humid air. This is also illustrated by the fact that a GM model of order two suffices to describe the material behavior in humid air but a GM model of order three is necessary to fit the material behavior in water. A possible interpretation is an additional relaxation effect of the pulp fiber wall in water.

Preparation and properties of pulp fibers treated with zinc oxide nanoparticles by in situ chemosynthesis

Abstract The efficiency of the growth and properties of zinc oxide (ZnO) nanoparticles (ZnO-NPs) on pulp fibers was investigated. ZnO-NPs were grown on pulp fiber surface via an in situ chemosynthesis method at different concentrations. The modified pulp fibers were characterized by different analytical tools including field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared (FTIR) spectroscopy, X-ray power diffraction (XRD) and thermogravimetric (TG) analysis. Ultraviolet (UV) absorption and antibacterial properties of the paper made from treated and untreated pulp fibers were analyzed. The results revealed that the rod-like ZnO-NPs were successfully grown onto the fiber surfaces without aggregation. As the precursor concentration increased from 0.01 to 0.07 mol l−1, the ZnO loading on the fibers increased from 4.2 to 23.4%, respectively. Compared to the untreated fibers, paper made from ZnO-treated fibers had a better UV absorption ability and antimicrobial effect against Escherichia coli and Staphylococcus aureus. However, the ZnO-treated pulp fiber reduced the zero span tensile index of the paper.

Effect of Morphological Properties of Pulp Fibers on the Sheet Uniformity in a Local Closed Place

Effect of Morphological Properties of Pulp Fibers on the Sheet Uniformity in a Local Closed Place

Influence of relative humidity on the strength of hardwood and softwood pulp fibres and fibre to fibre joints

Cellulosic materials are highly sensitive towards environmental changes such as temperature and especially towards humidity. Besides morphological changes like swelling and/or shrinking, the mechanical properties of pulp fibres and fibre to fibre joints change as well. The current study sets to elucidate the changes and the extent to which elevated or decreased relative humidity (RH) influences the load bearing capacity of individual hardwood and softwood fibres and joints. The device used for the measurements is a micro bond tester with a custom-built humidity chamber in which the humidity can be controlled in a range from 25 to 95% RH. Individual fibres and joints have been tested at 30, 50 and 80% RH after equilibration time of 120 min. The breaking load of individual softwood fibres and joints displayed a maximum breaking load at 50% RH, with the values showing a decreasing trend towards higher or lower RH. In case of hardwoods, no change in the breaking load of either individual fibres or fibre to fibre joints has been observed at different RH.

Chemical composition and fiber properties of fast-growing species in Latvia and its potential for forest bioindustry

Abstract Bioenergy, including energy from wood, currently provides about 9–13% of the total global energy supply. Every fibre of fast-growing wood has a value for its potential use as a material in both pulp and paper and wood chemical industries. The aim of this study was to assess the chemical composition and fibre’s properties of fast-growing species in Latvia – aspen, hybrid aspen, lodgepole pine, poplar and willow. Results showed a variation of cellulose, lignin, extractives and ash contents among the species. Kraft pulp yield and amount of residual lignin were measured and properties of pulp fibres determined. Form factor and fine content in pulp were measured. Poplar and aspen wood had the highest content of cellulose, while lodgepole pine had the highest lignin content in wood and the longest kraft pulp fibres. Willow had 20% of fines in pulp. Individual results suggest the most suitable application of each species.

Effects of Kneading Treatment on the Properties of Various Pulp Fibers

In this study, effects of kneading treatment on the properties of hardwood bleached kraft pulp (HwBKP), softwood bleached kraft pulp (SwBKP) and hardwood bleached chemi-thermo-mechanical pulp (HwBCTMP) were elucidated with a laboratory two-shaft kneader. Kneading treatment was performed at 30% (w/w) of pulp concentration and the number of passes through the kneader was adjusted from 0 to 10 passes. Then, changes in properties of pulp fibers were evaluated. It was found that fiber characteristics were influenced by kneading treatment. Fiber length was decreased with kneading while other morphological properties such as fiber width, curl and kink became increased as the number of passes through the kneader increased from 0 to 5 passes. The magnitude of changes in the morphological properties of softwood chemical pulp was the largest, followed by hardwood chemical pulp. The morphological properties of HwBCTMP were little influenced by kneading treatment. Swelling of fiber measured by WRV was increased with kneading except of HwBCTMP.

Fiber Properties of De-inked Old Newspaper Pulp after Bleaching with Hydrogen Peroxide

Hydrogen peroxide was applied to bleach recycled de-inked pulp from old newspaper (ONP) in this study. Following single-stage bleaching, the fiber properties of the pulp (viz. brightness, yield, fiber length, fiber charge, and strength properties) were determined. Finally, the crystal structure of cellulose, fiber surface morphology, and functional groups of the control pulp and the bleached pulp using hydrogen peroxide were analyzed by XRD, SEM, and FT-IR, respectively. The single-stage peroxide bleaching applied to the de-inked ONP pulp could produce a high brightness pulp of 58% ISO at a yield of 92%. Fiber length decreased after bleaching treatment. The crystallinity index of cellulose of de-inked ONP pulp during bleaching or rinsing treatment increased due to the dissolution of cellulose in amorphous regions and/or the dissolution or loss of non-cellulosic constituents (hemicelluloses and lignin). Hydrogen peroxide bleaching resulted in fibrillation and longitudinal tearing of the fiber surface due to delignification, which led to an increase in the paper strength. FT-IR data showed that the content of carboxylic acid groups decreased during peroxide bleaching. The main chromophore (conjugated carbonyl groups) and the guaiacyl units of the pulp were damaged after bleaching resulting in delignification.

Nanofibrillation of pulp fibers by twin-screw extrusion

The effect of the fibrillation process through a twin-screw extruder (TSE) on properties of pulp fibers was studied, considering the degree of both fibrillation and degradation of the fibers. Never-dried refined bleached kraft pulp (NBKP) was passed through a TSE several times at a high concentration of 28 wt%. The output of fibrillated fibers had a solid content up to ca. 50 wt%, and the material was in powder form. Characterizations of the morphology, dewatering speed, sedimentation, laser light scattering, scanning electron microscopy of cellulose suspensions, and light transmittance of resin-impregnated films showed that the fibrillation degree of the pulp was enhanced with a higher number of passes. However, the results from thermogravimetry, intrinsic viscosity, and X-ray diffraction analyses indicated that some degradation occurred during the fibrillation process in the TSE. In addition, the mechanical properties of the fibrillated pulp sheets reflected the effects of treatment on the fibrillation and degradation of the cellulose. For never-dried refined NBKP pulp, the best compromise in terms of fibrillation and degradation degree is between 3 and 14 passes, depending on the envisaged properties and applications. The possibility of nanocellulose production at the reported high solid contents is of great interest for industry.

Photocontrol of Mechanical Properties of Pulp Fibers and Fiber‐to‐Fiber Bonds via Self‐Assembled Polysaccharide Derivatives

AbstractPhotoresponsive pulp fibers are prepared by self‐assembly of photoactive cationic cellulose derivatives with pulp fibers in aqueous environment. Photoactive groups of the derivatives undergo 2π + 2π cycloaddition reaction under UV‐light irradiation. Fast photocrosslinking leads to the formation of the covalent bonds between the photoactive groups on the fiber surfaces. This results in drastic enhancement of the mechanical properties of the fiber network. Tensile strength and Z‐directional tensile strength increase by 81 and 84% compared to the original fiber network. Stiffness of the individual fibers increases by 60%. Such concept of controlling mechanical properties of the fiber materials by the light gives a possibility to design smart bio‐based materials and to increase end value of the fiber products.

Evaluation of Inter-fiber Bonding in Wood Pulp Fibers by Chemical Force Microscopy

Atomic force microscopy with chemically modified tips was used to evaluate the inter fiber bonding properties of typical wood pulp fibers. Using –OH functionalized AFM tips as a model of cellulosic pulp fiber surfaces, pull-off forces and work of adhesion were measured in aqueous media. Three distinct tip-surface interactions were identified from force-displacement curves, representing three typical surface conditions of wet pulp fiber surfaces: solid, swollen and micro-fibrillated. The work of adhesion calculated shows that van der Waals forces are the major contributing factor on non-swollen solid regions of fiber surfaces. The difference in inter-molecular bond strength of different pulp fibers is relatively small. The inter-fiber bonding properties of pulp fibers are mainly controlled by the surface deformability, which determines the area of molecular contact at fiber-fiber physical interaction points.

Alkali Extraction of Kraft Pulp Fibers: Influence on Fiber and Fluff Pulp Properties

The importance of hemicelluloses for the papermaking properties of pulp fibers is well documented. In the patent literature, it can be seen that there is also an interest in this type of modification of pulp fibers for use in absorption products. In this study, a Scandinavian softwood kraft pulp and a birch kraft pulp were alkali extracted at 3 different concentrations of NaOH (2%, 4% and 8% NaOH in the suspension). The alkali extraction removed a large part of the hemicelluloses from the pulp fibers and decreased the content of the charged groups. After extraction, the pulps were dried in the form of sheets (approx. 600 g/m2). The alkali extracted pulp fibers exhibited a greater decrease in swelling when re-wetted than untreated pulp. A significant increase in the curl index after extraction with 4% and 8% NaOH was also noted. The tensile strength index of the formed sheets increased at the lowest concentration of NaOH and, at the higher concentrations, a decrease was observed. The pulp sheets were dry defibrated at different defibration intensities and the performance of the resulting pulps in fluff pulp applications was studied. The air-laid fiber networks of softwood pulp fibers showed higher network strength than the networks of birch pulps. The birch pulp extracted at the highest alkali level tended to give the highest network strength. The results from the network strength tests also indicated that the increased curl of the fibers from the softwood pulp extracted at the highest alkali level rendered a more flexible fiber network. In water absorption tests, the alkali treated softwood fibers tended to give networks with a somewhat enhanced water holding capacity under pressure.

Wet strength development in sisal cellulose fibers by effect of a laccase–TEMPO treatment

The aim of this study was to investigate the oxidation of sisal pulp fibers by laccase–TEMPO system which had never previously been examined. High cellulose content sisal fibers were treated with laccase from Trametes villosa and a varying amount of TEMPO in order to evaluate the potential of laccase–TEMPO system to improve the paper physical properties of pulp fibers. The effect of the oxidative treatment on the carboxyl group content and viscosity of pulp fibers was examined. The resulting papers were analyzed in terms of strength-related properties, water absorbency capabilities and fiber morphology. Oxidation of sisal pulp by laccase–TEMPO system resulted in a very important improvement of wet strength of the resulting papers, suggesting the formation of a substantial amount of aldehyde groups in cellulose chains providing interfiber bonding through hemiacetal linkages.

Characterization of wood fibers using fiber property distributions

The properties of pulp fibers have a strong influence on their papermaking potential. Dimensions and physical properties of fibers vary considerably. The papermaking potential of pulp is currently evaluated solely based on the mean values of fiber properties, for instance fiber length. Property distributions with the same mean value can be totally different and therefore a more suitable approach in determining pulp quality is needed. The distributions of fiber properties are likely to be more important than their mean values in controlling pulp quality, as the heterogeneity of the papermaking material is evident. Various problems associated with mean values are considered. A better understanding of characteristic distributions and their meaning in predicting paper properties can prove a significant aid in improving the quality control of pulp.

Micromechanical understanding of the cell-wall structure

For improving properties of pulp fibres, a better understanding of the relationships between its macroscopic mechanical properties, fibre ultrastructure, and properties of the wood polymers is important. This paper discusses such relations between elastic properties of fibres, their matrix structure and the wood polymer elastic constants. It is argued that an orientation of all of the wood polymers in the direction of the cellulose microfibrils is most likely. The elastic longitudinal modulus of cellulose is well described by the value of 134 GPa dominating the longitudinal fibre properties. In the transverse direction the amorphous polymers play a more important role. To cite this article: L. Salmén, C. R. Biologies 327 (2004).

Alkali–methanol–anthraquinone pulping of Miscanthus x giganteus for thermoplastic composite reinforcement

AbstractThe potential of pulp fiber–reinforced thermoplastics is currently not fully explored in composites. One of the main reasons is that pulp fibers are extracted for the use in papermaking and are thus not optimized for use as reinforcements in thermoplastics. Furthermore, currently used processing methods constitute several severe thermomechanical steps inducing premature degradation of the fibers. A systematic development of these composite materials requires the study of both these aspects. The goal of this work was to optimize fiber extraction against properties relevant to the reinforcement of thermoplastics. To this end, thick‐walled Miscanthus x giganteus pulp fibers were selected. The fibers were pulped by the alkaline–methanol–anthraquinone process. An unreplicated factorial design was applied to determine the effect of key operating variables on fiber thermal stability and mechanical properties. The thermomechanical properties of pulp fibers depend primarily on the morphology and chemical composition of the fiber resource in terms of the respective amounts of lignin, hemicellulose, and cellulose, all strongly influenced by the choice of pulping conditions. Optimal pulping parameters were identified, allowing production of fibers thermally stable up to 255°C with an aspect ratio of 40, a straightness of 95%, and tensile strength as high as 890 MPa. Specific stiffness and strength values with respect to density and material cost of 56 GPa m−3 $−1 and 820 MPa m−3 $−1 were highly competitive with glass fibers, with corresponding values of 15 GPa m−3$−1 and 270–490 MPa m−3 $−1, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2132–2143, 2004

Relation between mechanical properties of pulp fibers and the activation energy of softening as affected by sulfonation

Relation between mechanical properties of pulp fibers and the activation energy of softening as affected by sulfonation