Fibrillation Of Fibers Research Articles

Fabraction of edible bio-nanocomposite coatings from pectin-containing lignocellulosic nanofibers isolated from apple pomace

Minimally processed fruits are increasingly demanded in modern society, but the management of perishable waste pomaces (WPs) and the products' short shelf-life are still big issues. Here, a facile approach of reconstruing apple pomace (AP) into edible bio-nanocomposite coatings of fresh-cutting apple slices was successfully developed through alkaline demethylation followed by high-pressure homogenization. The fibrillation of AP fibers is largely improved by -COO− at a concentration of 1.23 mmol g−1, which is released through alkaline demethylation of pectin, instead of relying on intricated or costly cellulose modifications. The average width of AP nanofibers (AP-NFs) downsizes to 18 nm. By casting, AP-NFs fabricate homogeneous films with comparable transparency (56 % at 600 nm), superior mechanical strength (6.4 GPa of Young modulus and 81.7 MPa of strength) and oxygen barrier properties (79 mL μm m−2 day−1 bar−1), and non-toxicity. Moreover, the AP-NF coatings effectively extend shelf life of apple slices by inhibiting browning and respiration, and retain firmness. This research demonstrates a way to valorize WPs as edible coatings for fruit packaging.

Producing Cellulose Microfibrils at a High Solid Content with and without Mechanical or Enzymatic Pretreatment.

This study conducted a detailed evaluation of the feasibility of producing cellulose microfibrils (CMF) from a kraft-bleached hardwood pulp at high solid contents with and without pretreatments. CMFs produced by planetary ball milling at solid contents 17 and 28% were compared with those from 1 to 5% under the same milling conditions. Fiber pretreatments using a commercial endoglucanase and mechanical refining using a laboratory PFI mill were also applied before ball milling at a solid content of 28%. Two mechanisms of fiber fibrillation were identified from the results obtained: (i) ball and fiber/fibril interactions─the primary mechanism and (ii) interfiber/fibril frictional and tensional interactions─the secondary mechanism. The secondary mechanism plays an important role only in early-stage fibrillation and became less important as fibrillation proceeded in the later stage toward nanofibrillation. Improving fiber dispersion at lower solid content facilitated fibrillation. Endoglucanase pretreatment substantially shortened fibers to result in a "pulverized-like" CMF with short fibrils at an extended milling time. Mechanical refining of fibers facilitated fibrillation to result in CMFs with a morphology similar to that from runs without any fiber pretreatment but for a much shorter milling time. Both CMF water retention value (WRV) measurements and CMF suspension sedimentation experiments showed results consistent with imaging observations. The insights gained through this study provide relevant information with commercial significance regarding CMF production at high solids, which is not currently available in the literature.

All-polyamide nanofibrillar composites by in situ fibrillation of aramid fibers

All-polyamide composites containing up to 30 vol% highly dispersed PPTA nanofibrils with diameters in the range 50–500 nm were prepared by melt-compounding polyamide 6,10 (PA610) with chopped poly(p-phenylene terephthalamide) (PPTA) fibers in the temperature range 260–300 °C using a twin-screw extruder. Injection moldings prepared from these composites showed not only large increases in tensile strength with respect to the unmodified PA610 matrix at temperatures well below the matrix melting point but also significant increases in melt elasticity. The melt elasticity was further enhanced by high-temperature heat treatments under quiescent conditions. It is suggested that the implied interfacial reinforcement may involve transamidation, which is known to occur extensively in polyamide melts.

GRINDING OF FIBROUS SEMI-FINISHED PRODUCTS AS A MECHANOCHEMICAL PROCESS. MATHEMATICAL MODELING

It is known that the process of grinding fibrous semi-finished products proceeds in the form of four successive stages, accompanied by complex processes of fibrillation and hydration of fibers subjected to mechanical action. The development of these processes over time determines the dynamics of changes in cellulose fiber, which ultimately leads to the formation of the necessary paper-forming properties. The paper shows that the representation of the grinding of fibrous semi-finished products as a mechanochemical process makes it possible to formulate a mathematical model of the grinding dynamics based on the principles of formal kinetics. The latter makes it possible to single out the stages of the milling process in the form of a standard kinetic mechanism of successively occurring reactions. The corresponding model is presented as a system of ordinary differential equations with constant coefficients, the solution of which presents no fundamental difficulties. Since it is not the degree of destruction that is determined experimentally, but the degree of grinding, it is proposed to present the relationship between these values as a power series with a limitation in the form of a linear approximation. However, due to the large dimension, the parametric identification of the model has fundamental difficulties. The paper proposes a reduction method that allows overcoming the problem. The corresponding parameters are identified by comparing the model and the array of experimental data. The presented approach makes it possible to obtain an adequate closed mathematical description of the dynamics of grinding fibrous semi-finished products.

INFLUENCES OF ALKALI PRETREATMENT ON LYOCELL WOVEN FABRIC PROPERTIES AFTER ABRASION

In this study, alkali pretreatment in various concentrations were applied to Lyocell woven fabrics to decrease the fibrillation tendency of fibers and the influences of alkali pretreatment on tensile and tearing properties of Lyocell fabrics after abrasion were investigated. Alkali pretreatment reduced fibrillation of Lyocell fibers. However, fabric shrinkage occurred because of the increased volume and damaged twisted structure of yarns due to the lateral fiber swelling. The warp/weft densities and crimp ratios increased as the alkali concentrations increased. The breaking and tearing loads of untreated Lyocell fabrics were higher than those of alkali pretreated fabrics since the strength loss caused by alkali pretreatment. The abrasive load caused fiber breakages and fiber entanglements on fabrics and decreased the both breaking and tearing loads. The weave types with long floating interlacements on the fabric surface were more severely damaged by exposing to abrasive load and resulted as higher strength reduction.

Development of Eco-Friendly Method for Degumming of Eri Cocoons

In this study, a new eco-friendly degumming technique was developed for Eri cocoons without any chemicals. A newly developed eco-Eri degumming process was tried at 110 °C, 120 °C, 130 °C and 140 °C temperatures for 10, 20 and 30 min with soft and hard water. The novel eco-friendly degumming method was compared with the existing method of degumming viz. Soap-soda along with the enzymatic method. After degumming, weight loss per cent, changes in the fibre surface morphology concerning SEM imaging and fibre properties concerning tensile strength and elongation were studied. The eco-Eri degumming method at 130 °C for 30 min using soft water removed the maximum sericin content (degumming loss 15.7%) from Eri cocoon shells and had optimum degumming efficiency. In the eco-Eri degumming method, the degummed Eri cocoons were uniformly softened. The soap soda method of degumming resulted in 14.5% weight loss whereas enzymatic degumming resulted in a maximum of 13% weight loss (12% dosage). Enzymatic degumming significantly reduced the tensile strength but no results found in the tensile properties of Eri silk fibres were observed in new eco-friendly and soap-soda methods. SEM images indicated optimal fibre surface with the smoother surface until 130 °C, but fibre damage and fibrillation occurred at 140 °C and also with the Soap-soda method. An optimal condition for degumming Eri cocoons with the new eco-Eri degumming process is 130 °C for 30 min using soft water. The eco-Eri degumming method is better compared to other methods used presently in the industry.

Production of low-density and high-strength paperboards by controlled micro-nano fibrillation of fibers

One of the critical challenges in the fiber-based packaging industry is to produce low-density paperboards with high functionality and attractive cost structure. In this study, we examine how control of the hierarchical fiber swelling can be used to enhance bonding and generate a low-density fiber network with excellent strength properties. Here, the osmotic pressure inside the cell wall is increased by adding phosphate groups with a deep eutectic solvent (DES) functional drying method. Together with mechanical refining, this process causes the fibril aggregates to split and swell up massively. This effect was measured by a novel thermoporosimetry analysis method. The treated fibers have enhanced external fibrillation, fibrillar fines and bonding potential. When mixed with relatively stiff, unrefined fibers, a well-bonded sheet with lower density than a conventionally refined reference sheet was achieved. The results suggest that pulp fibers can be “nanoengineered” to enhance performance without the complications of producing and adding nanocellulose.

Factor and cluster analyses of the structure of correlations between high consistency pulp properties during refining and paper strength characteristics

This article analyses high-consistency pulp refining using a disk refiner. During the experiment, the size of the gap between the rotor and stator cutters (0.5 to 1.5 mm), rotor speed (2,000 to 2,500 rpm), pulp consistency (10 to 20%), and freeness value (15 to 60 °SR) of the pulp were varied. The refining results were characterised by changes in 10 output parameters: morphological properties of cellulose fibres (average length, width, fibrillation index, water retention value, average kink angle, and coarseness) and the physical and mechanical characteristics of handsheets (breaking length, bursting strength, tearing resistance, and folding endurance). A total of 56 observations were made on the samples. Factor and cluster analysis methods were used to study the structure of correlations between the output parameters. More than 96% of the total dispersion of all output parameters was due to a change in two latent (hidden) factors: the first one was responsible for 79.6% of the dispersion and is presumably identified as the degree of external fibre fibrillation and the second one (16.6% of the dispersion) as fibre flexibility (including coarseness and average kink angle).

Engineering biomimetic cellulose fabric for sustainably and durably cooling human body

It is essential and challenging to develop sustainable and durable passive radiative cooling materials for long-term effectively maintaining human thermal comfort when undergoing intensified global warming in our low-carbon society. Herein, inspired by the distinct structure-property relationship of fruits-branches in fruiter, this work designs an approach of fibrillation of cellulosic fibers (branches of fruiter) followed by in-situ synthesis of SiO2 nanoparticles (fruits of fruiter) easily to prepare sustainable, robust, customizable, and scalable cooling cellulose fabric. Such coupling strategy of cellulosic-fiber fibrillation and SiO2 in-situ growth strongly roughens cellulose fabric, more specifically, sufficient micro- and nano-sized cellulose fibrils and SiO2 particles, which enables our cooling cellulose fabric to effectively reflect solar light with 97% reflectance (0.4–1.0 µm) and emit mid-infrared light with 0.97 emissivity (8–13 µm). As a result, the developed cooing cellulose fabric spontaneously cools the human body with a temperature drop of 7.4 °C in high-temperature summer. It should be noted that the developed strategy realizes extraordinary adhesion performance between nanosized SiO2 and fibrillated cellulosic fibers, endowing cooling cellulose fabric with durable yet effective cooling distinction despite enduring 100-time mechanical washing and 100-day exposure to air, as well as high strength (∼48 MPa), desirable moisture evaporation rate and breathability. The present work demonstrates a promising strategy how durability, functionality, and customizability can be integrated in future material design.

Polydopamine modified cellulose nanocrystals (CNC) for efficient cellulase immobilization towards advanced bamboo fiber flexibility and tissue softness

Herein, a green facile approach to improve the flexibility of unbleached bamboo kraft pulp (UBKP) via an immobilized enzyme technology is proposed. Polydopamine (PDA) acts as versatile modification and coating materials of cellulose nanocrystals (CNC) for assembling versatile bio-carriers (PDA@CNC). Cellulase biomacromolecules are efficiently immobilized on PDA@CNC to form cellulase@PDA@CNC nanocomposites. The relative enzyme activity, temperature/pH tolerance, and storage stability of cellulase were significantly improved after immobilization. The degree of polymerization treated UBKP decreased by 5.42 % (25 U/g pulp) compared to the control sample. The flexibility of treated fibers was 6.61 × 1014/(N·m2), which was 96.93 % higher (25 U/g) compared to the control and 3.88 times higher than that of the blank fibers. Cellulase@PDA@CNC performs excellent accessibility to fiber structure and induces high degree of fibrillation and hydrolysis of UBKP fibers, which contributes high softness of obtained tissue handsheets. The bio-carrier PDA@CNC within paper framework may further enhance tissue tensile strength. This study proposes a practical and environmentally friendly immobilization approach of cellulase@PDA@CNC for improving the hydrolysis efficiency and flexibility of UBKP fibers, which provides the possibility to maintain the strength of tissue paper while improving its softness, thus broadening the high-value application of immobilized enzyme technology in tissue production.

3D-printed polylactide composites reinforced with short lyocell fibres – Enhanced mechanical properties based on bio-inspired fibre fibrillation and post-print annealing

3D-printed polylactide composites reinforced with short lyocell fibres – Enhanced mechanical properties based on bio-inspired fibre fibrillation and post-print annealing

High-Consistency Mechano-Enzymatic Fibrillation of Bamboo Pulp Fibers to Produce Precursors for Highly Fibrillated Cellulose and Dense Films with Multifunctionalities

High-Consistency Mechano-Enzymatic Fibrillation of Bamboo Pulp Fibers to Produce Precursors for Highly Fibrillated Cellulose and Dense Films with Multifunctionalities

Analyses of the effects of fiber diameter, fiber fibrillation, and fines content on the pore structure and capillary flow using laboratory sheets of regenerated fibers

Abstract The aim of this work is to investigate the influence of fiber fibrillation and fines on the pore structure of well-defined regenerated fiber sheets as well as the water flow through the sheet. For this purpose, sheets were produced with refined, fibrillated fibers only, with unfibrillated fibers and fines, as well as with fibrillated fibers and fines. Next, the samples were analyzed by brightfield and fluorescence microscopy, mercury porosimetry, and an ascending test. Both the fibrils and the added fines reach into the pores between the fibers or are deposited there. As a result, pore size decreases and capillary flow slows down. The two effects overlap when the fiber surface is fibrillated and fines are present. Sheets with thicker fibers form a pore structure with larger pores in between the fibers. However, such a change in pore size has no significant influence on the flow of water through the sheet in the performed ascending tests. It is shown that a statistical model with the parameters fibrillation and fines content can be used to describe the ascending rate nearly as well as the Lucas–Washburn equation. Consequently, the equation could be improved by the addition of further fiber and sheet properties.

Role of external fibrillation in high-consistency pulp refining

The mechanical and hydrodynamic phenomena occurring in the refining zones of disc refiners cause fibres to undergo fibrillation. This paper presents a study of the changes occurring during fibre fibrillation as expressed in terms of the fibrillation index when refining pulp with a 10%, 15%, and 20% consistency. The influences of the tangential force of a circular bar and a straight bar on fibre fibrillation were compared. The changes in the tangential force are shown to depend on the angle between the tangent to the cutting edge and the radius from the centre of the disk to the tangency point. Increasing the angle between the tangent to the cutting edge and the radius from the centre of the disk to the tangency point gives higher fibrillation index values. The study revealed a relationship between fibre fibrillation and the strength characteristics of handsheets.

Biodegradable Poly(butylene adipate-co-terephthalate) Nanocomposites Reinforced with In Situ Fibrillated Nanocelluloses

The enhancement of mechanical properties is highly required for the expanded applications of biodegradable polymers like poly(butylene adipate-co-terephthalate) (PBAT). The use of nanocellulose as reinforcing fillers is one of the effective approaches while preserving the biodegradability of polymers, but the dispersion of nanofibers in polymer matrixes is a great challenge. Here, we report an in situ fibrillation method to prepare nanocellulose-reinforced PBAT composite films with superior mechanical properties and enhanced degradability while promoting the easy dispersion of natural plant fibers in the polymer matrix, which overcome the limitation of natural fiber composites for thin film applications. A hemicellulose-rich holocellulose fiber was selected and silanized prior to melt compounding with PBAT, in which in situ fibrillation of fibers and the dispersion of in situ fibrillated cellulose nanofibrils (CNFs) occurred simultaneously. The nanostructure, mechanical properties, and degradability of the resulting composite films were characterized. Compared with pristine PBAT, the incorporation of 1 wt % CNF fillers increased the tensile modulus by 82% while possessing a tensile strength of 26 MPa, an elongation of 372%, and a toughness of 75 MJ/m3, surpassing most reported data. Moreover, the degradability of PBAT was enhanced as well. Altogether, this study paves a new way of making biodegradable nanocomposites, which expand the application areas, especially where films are required.

Optimized Lytic Polysaccharide Monooxygenase Action Increases Fiber Accessibility and Fibrillation by Releasing Tension Stress in Cellulose Cotton Fibers.

Lytic polysaccharide monooxygenase (LPMO) enzymes have recently shaken up our knowledge of the enzymatic degradation of biopolymers and cellulose in particular. This unique class of metalloenzymes cleaves cellulose and other recalcitrant polysaccharides using an oxidative mechanism. Despite their potential in biomass saccharification and cellulose fibrillation, the detailed mode of action of LPMOs at the surface of cellulose fibers still remains poorly understood and highly challenging to investigate. In this study, we first determined the optimal parameters (temperature, pH, enzyme concentration, and pulp consistency) of LPMO action on the cellulose fibers by analyzing the changes in molar mass distribution of solubilized fibers using high performance size exclusion chromatography (HPSEC). Using an experimental design approach with a fungal LPMO from the AA9 family (PaLPMO9H) and cotton fibers, we revealed a maximum decrease in molar mass at 26.6 °C and pH 5.5, with 1.6% w/w enzyme loading in dilute cellulose dispersions (100 mg of cellulose at 0.5% w/v). These optimal conditions were used to further investigate the effect of PaLPMO9H on the cellulosic fiber structure. Direct visualization of the fiber surface by scanning electron microscopy (SEM) revealed that PaLPMO9H created cracks on the cellulose surface while it attacked tension regions that triggered the rearrangement of cellulose chains. Solid-state NMR indicated that PaLPMO9H increased the lateral fibril dimension and created novel accessible surfaces. This study confirms the LPMO-driven disruption of cellulose fibers and extends our knowledge of the mechanism underlying such modifications. We hypothesize that the oxidative cleavage at the surface of the fibers releases the tension stress with loosening of the fiber structure and peeling of the surface, thereby increasing the accessibility and facilitating fibrillation.

Ambient-conditions spinning of functional soft fibers via engineering molecular chain networks and phase separation

Producing functional soft fibers via existing spinning methods is environmentally and economically costly due to the complexity of spinning equipment, involvement of copious solvents, intensive consumption of energy, and multi-step pre-/post-spinning treatments. We report a nonsolvent vapor-induced phase separation spinning approach under ambient conditions, which resembles the native spider silk fibrillation. It is enabled by the optimal rheological properties of dopes via engineering silver-coordinated molecular chain interactions and autonomous phase transition due to the nonsolvent vapor-induced phase separation effect. Fiber fibrillation under ambient conditions using a polyacrylonitrile-silver ion dope is demonstrated, along with detailed elucidations on tuning dope spinnability through rheological analysis. The obtained fibers are mechanically soft, stretchable, and electrically conductive, benefiting from elastic molecular chain networks via silver-based coordination complexes and in-situ reduced silver nanoparticles. Particularly, these fibers can be configured as wearable electronics for self-sensing and self-powering applications. Our ambient-conditions spinning approach provides a platform to create functional soft fibers with unified mechanical and electrical properties at a two-to-three order of magnitude less energy cost under ambient conditions.

Physicochemical properties of sodium alginate from brown algae Sargassum aquifolium and Sargassum cinereum

Synthesis and characterization of sodium alginate from Sargassum aquifolium dan Sargassum cinereum have been successfully performed. S. aquifolium and S. cinereum were collected from the Dompu Islands, West Nusa Tenggara, Indonesia. Extraction was performed by acid pathway, due to cell disruption and the addition of Na2CO3 for extraction. The addition of HCl was to convert acid alginate into alginate, then transformed acid alginate into sodium alginate using NaOH. NaOCl and IPA were used for purification. Physicochemical properties were characterized using SEM-EDS, FTIR, and TG/DTG. The morphological structure of synthetic sodium alginate shows layer structure and fiber fibrils. Sodium alginate contained C, O, Na, and Cl elements. FTIR spectrum indicated the presence of functional groups at the following wavelengths: OH at 3343 cm−1, CH2 at 2915 cm−1, CO double bonds at 1614 cm−1, and fingerprint indicated by the presence of uronic acid, which functioned as the CH group stretched at 935 cm−1. The sodium alginate sample shows a three-step thermal degradation pattern. The first step was starting at 41.7 °C associated with dehydration and was followed by 206.4 and 241 °C associated with decomposition. TGA/DTG results showed a reduction in thermal stability at 250–300 °C. It is suitable for modification and application.

Endoglucanase effects on energy consumption in the mechanical fibrillation of cellulose fibers into nanocelluloses

Enzymatic processing is considered a promising approach for advancing environmentally friendly industrial processes, such as the use of endoglucanase (EG) enzyme in the production of nanocellulose. However, there is ongoing debate regarding the specific properties that make EG pretreatment effective in isolating fibrillated cellulose. To address this issue, we investigated EGs from four glycosyl hydrolase (GH) families (5, 6, 7, and 12) and examined the roles of the three-dimensional structure and catalytic features, with a focus on the presence of a carbohydrate binding module (CBM). Using eucalyptus Kraft wood fibers, we produced cellulose nanofibrils (CNFs) through mild enzymatic pretreatment, followed by disc ultra-refining. Comparing the results with the control (without pretreatment), we observed that GH5 and GH12 enzymes (without CBM) reduced fibrillation energy by approximately 15 %. The most significant energy reduction, 25 and 32 %, was achieved with GH5 and GH6 linked to CBM, respectively. Notably, these CBM-linked EGs improved the rheological properties of CNF suspensions without releasing soluble products. In contrast, GH7-CBM exhibited significant hydrolytic activity, resulting in the release of soluble products, but did not contribute to a reduction in fibrillation energy. This discrepancy can be attributed to the large molecular weight and wide cleft of GH7-CBM, which led to the release of soluble sugars but had little impact on fibrillation. Our findings suggest that the improved fibrillation observed with EG pretreatment is primarily driven by efficient enzyme adsorption on the substrate and modification of the surface viscoelasticity (amorphogenesis), rather than hydrolytic activity or release of products.

Soda pulping of sunn hemp (Crotalaria juncea L.) and its usage in molded pulp packaging

Petroleum-based materials are often used in the packaging industry. However, the single use value of such products can be problematic with regard to proper waste disposal. As such, molded pulp packaging can be used as an alternative, given its ease of recycling, composting, and eventual biodegradation. In this work, we aims to study the pulp properties of sunn hemp and its usage as molded pulp products. For this purpose, unbleached beaten and unbeaten soda pulps derived from the whole stem of sunn hemp were examined for their fiber morphology, fibrillation, fiber classification, and physical properties. The sunn hemp pulp was subsequently molded using a batch molding machine. To determine the hydrophobicity of the molded pulp products, the molded samples were manufactured with and without additives. Finally, some properties of the molded pulp products were examined and compared with the commercially available bleached bagasse molded pulp products. It was observed that the molded products made from sunn hemp pulp with additives had a higher water contact angle than that of the commercial products. In terms of general usage, the molded products from sunn hemp pulp with additives were found to be capable of storing hot water, hot cooking oil, as well as microwaving water. We concluded that the sunn hemp pulp could be used as an alternative fibrous raw material in the production of molded pulp packaging.