Microfibrillated Cellulose Fibers Research Articles

A comparative study of lignin-containing microfibrillated cellulose fibers produced from softwood and hardwood pulps

The expanding field of lignin-containing nanocellulose offers a sustainable alternative to fossil-based substances in applications such as packaging, coatings, and composites. This has underscored the importance to explore the impact of raw materials due to the complexities of lignin structures and different raw fiber characteristics, which plays a significant role in determining the properties of the resultant lignin-rich cellulose materials. This study presents a detailed investigation and comparison on the production and structure-property relationships of lignin-containing microfibrillated cellulose (LMFC) fibers prepared from unbleached softwood and hardwood kraft pulps. The microfibrillation process was analyzed for both softwood and hardwood pulps, comparing the results across various stages of fibrillation. Distinguishing features of lignin structures in softwood and hardwood pulps were identified through Py-GC/MS analysis. Additionally, Digital Image Correlation was employed to investigate the varying failure patterns in LMFC films derived from different wood species. Softwood-derived LMFC films demonstrate less strain-concentrated regions and strain variation, attributed to the formation of more physical crosslinking joints by the elongated fibers. Consequently, softwood-origin LMFC films displayed superior load-sharing and enhanced tensile strength (287 MPa) compared to those derived from hardwood. Additionally, the denser lignin structures in unbleached softwood pulp further boosted the stiffness of resultant softwood-derived films. Upon recycling, LMFC films exhibited superior recovery of mechanical properties following drying, suggesting their significant potential for widespread commercial use.

Tri-Layer Nonwoven Separator with Thermal Shutdown Function Fabricated through a Facile Papermaking Method for High-Safety Lithium-Ion Battery

Lithium-ion batteries have long been plagued by the safety issue of thermal runaway. Improving the thermal stability and developing the thermal shutdown function of the separators are considered reliable solutions. Therefore, in this work, a tri-layer structured nonwoven separator with a thermal shutdown function has been prepared via the papermaking method. The separator comprises a polyethylene fiber layer, a microfibrillated cellulose fibers layer, and a polyethylene terephthalate nonwoven fabric layer. The polyethylene fiber layer endows the separator with a thermal shutdown function at 135 °C. The middle polyethylene terephthalate nonwoven layer provides support, while the microfibrillated cellulose fibers adjust the pore size. The separators exhibit excellent thermal stability, no shrinkage after heat treatment at 200 °C, and a wide thermal shutdown temperature window, thereby enhancing battery safety. This research provides an approach to fabricating high-safety thermal shutdown separators.

Preparation of micro-fibrillated cellulose fibers by a simple two-step refining process for paper- based flexible electronic devices

Cellulose micro/nano-materials are potential substrates for energy storage/ electronics applications. However, developing efficient/cost-effective technologies that can obtain these micro/nano-materials suited for flexible electronics continue to be a challenge. In this study, we report a simple process for extracting micro-fibrillated cellulose fibers from conventional bleached kraft pulp that are particularly applicable to flexible electronics applications. The process is made of two step refining: 1) refining in a Valley beater, and 2) further fibrillation in a ball mill. The Valley beater is to induce fibrillation of pulp fibers as a result of compression and shearing forces. Subsequently, the partially fibrillated cellulose fibers are further subjected to ball milling to obtain micro-fibrillated cellulose fibers (MFCs). These MFCs have a much higher specific surface area than the conventional pulp fibers due to fibrillation and reduction in fiber size, which leads to favorable properties to the as- prepared MFCs network, including high transparence, and high tensile strength. The MFCs paper exhibits excellent transparency of 82% at 550 nm (a significant increase of about 56% for the control), with exceptionally high tensile strength (35.16 MPa). Thanks to the high surface area of these MFCs, silver nanowires (AgNWs) can be well distributed into the MFCs network so that conductive paper with high conductivity was prepared. The MFCs/AgNWs composite paper was then assembled into the paper-based triboelectric nanogenerator (P-TENG) device, which shows excellent performance. The MFCs/AgNWs composite paper- based P-TENG system can also serve as self-powered sensors for monitoring human motions. This work provides a method for the production of micro- fibrillated cellulose fibers that can be applied for the production of flexible electronic devices.

Enhanced flame resistance of cellulose aerogel by ammonium polyphosphate for heat insulation

Cellulose aerogels are a potential candidate for heat insulation, but one of their drawbacks is high flammability hindering their applications in practice. This study synthesized cellulose aerogels from microfibrillated cellulose fibers (MFC) extracted from discarded pineapple leaves. The procedure started with simply mixing the extracted fibers with polyamide amine-epichlorohydrin (PAE) as a chemical crosslinker and ammonium polyphosphate (APP) (10-20%) as a green and effectively flame-resistant additive, followed by freeze-drying. The produced aerogels are characterized in terms of their morphology, thermal stability and conductivity, and flame resistance via advanced and standardized methodologies including Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), thermal conductivity measurement by a heat flow meter, and UL94 horizontal burning test. The flame-resistant cellulose aerogels exhibit ultra-low density (25.5-26.8 mg/cm3), high porosity (98.0-98.2%), excellent heat insulation (35.9-36.7 mW/m۰K), and are completely flame-resistant. In addition, the varied APP content (10-20%) shows little effect on the density, heat conductivity, and thermal stability of the flame-resistant cellulose aerogels in comparison with that of the neat cellulose aerogel. Based on the findings, the synthesized flame-resistant cellulose aerogels are considered a promising bio-based heat insulation material.

High‐performance nano‐biocomposite ionic soft actuators based on microfibrillated cellulose/ionic liquid electrolyte membrane

AbstractHigh‐performance electro‐responsive ionic soft actuators with low actuation voltage, large bending strain, and ecofriendly functionalities have received great interest in soft robots, biomimetic robots, biomedical devise, flexible electronics, and wearable devices. Herein, we report a novel ionic soft actuator using biofriendly microfibrillated cellulose (MFC) and PEDOT:PSS, which exhibited a large peak‐to‐peak displacement (11.21 mm) mm under a sinusoidal excitation of 1.5 V at 0.1 Hz, low actuation voltage, wide driving frequency, excellent actuation durability (98% retention for 2 h), and excellent controllability, due to the strong ionic interactions of MFC fibers with cations and anions of ionic liquid (IL). Furthermore, the helical MFC‐IL ionic actuator was successfully designed, displaying that the radical displacements of the helical actuator could be controlled by changing the applied frequency and voltage. Therefore, the proposed ionic actuator as well as its helical design will offer an available pathway for guiding the development of artificial muscles, biomedical active devices, soft robots, flexible electronics, and soft electronics.

Tensile behavior analysis combined with digital image correlation and mechanical and thermal properties of microfibrillated cellulose fiber/ polylactic acid composites

Microfibrillated cellulose (MFC) employed as reinforcement of polymeric matrices can increase elastic modulus, stiffness and strength of a composite. In this work, the assessment of the mechanical, thermal properties and tensile tests assisted by digital image correlation (DIC) was performed for curaua fiber MFC-reinforced polylactic acid (PLA) composites as a function of MCF content. First, MFC was incorporated into PLA using a solvent exchange technique and subsequent polymer solubilization to produce master batch composites. Then, more PLA was added to obtain composites with 0.5 and 1.5 wt% MFC by using double screw extrusion and injection molding. As a result, the addition of MFC caused the flexural, tensile, indentation, impact and modulus strengths to increase compared to those of pure PLA. The deformation gradient obtained from DIC verified that the 0.5 wt% MFC/PLA composite presented greater homogeneity in relation to load dispersion, corroborating the higher rigidity, maximum stress, and Poisson's ratio.

One-pot preparation of micro-fibrillated cellulose fiber (MCF) through the synergistic action of g-C3N4 and a diluted acid

g-C3N4 with good cellulose affinity has the ability to peel microfibrils from the fiber surface through the interaction between g-C3N4 and cellulose. Hydrated hydrogen ions can accelerate the dissociation of the hydrogen bond between microfibrils.

High-performance microfibrillated cellulose-based low voltage electroactive ionic artificial muscles in bioinspired applications

The development of electroactive high-performance biofriendly artificial muscles with large mechanical bending deformation, fast response time, low actuation voltage, and excellent durability is highly desirable for human friendly electronics such as soft robots, active biomedical devices, wearable devices, and flexible haptic displays. Herein, we report a novel ultralow voltage high-performance ionic artificial muscle based on microfibrillated cellulose (MFC), ionic liquid (IL) as a plasticizer, and conducting polymer poly(3,4-ethylene dioxythiophene)-polystyrene sulfonate (PEDOT: PSS) as electrodes. The proposed MFC-IL biocomposite membrane was fabricated through doping of MFC with IL. The PEDOT:PSS layers were uniformly deposited on surfaces of the MFC-IL membrane by using the dip-coating method. The designed MFC-IL actuator demonstrated a large bending strain (0.31% under a sinusoidal input voltage of ±1.5 V at 0.1 Hz), low actuation voltage (<2 V), fast response time (<2.5 s), and excellent actuation durability (98% retention for 2 h), all of which were mainly due to its relatively large specific capacitance (115.2 mF cm−2) and tuned mechanical properties, resulting from the strong ionic interactions and crosslinking of MFC fibers with IL. More importantly, bioinspired applications including the grapple robot, bionic medical stent, and artificial soft robotic finger have been successfully realized. Therefore, the newly designed MFC-IL ionic soft actuator and its bioinspired robotic designs will provide a viable way for developing next-generation artificial muscles, soft robotics, active medical devices, and flexible displays.

Preparation of Breathable Cellulose Based Polymeric Membranes with Enhanced Water Resistance for the Building Industry.

This study focuses on the development of advanced water-resistant bio-based membranes with enhanced vapour permeability for use within building envelopes. Building walls are vulnerable to moisture damage and mold growth due to water penetration, built-in moisture, and interstitial condensation. In this work, breathable composite membranes were prepared using micro-fibrillated cellulose fiber (CF) and polylactic acid (PLA). The chemical composition and physical structure of CF is responsible for its hydrophilic nature, which affects its compatibility with polymers and consequently its performance in the presence of excessive moisture conditions. To enhance the dispersibility of CF in the PLA polymer, the fibers were treated with an organic phosphoric acid ester-based surfactant. The hygroscopic properties of the PLA-CF composites were improved after surfactant treatment and the membranes were resistant to water yet permeable to vapor. Morphological examination of the surface showed better interfacial adhesion and enhanced dispersion of CF in the PLA matrix. Thermal analysis revealed that the surfactant treatment of CF enhanced the glass transition temperature and thermal stability of the composite samples. These bio-based membranes have immense potential as durable, eco-friendly, weather resistant barriers for the building industry as they can adapt to varying humidity conditions, thus allowing entrapped water vapor to pass through and escape the building, eventually prolonging the building life.

Using cellulose fibers to fabricate transparent paper by microfibrillation

Fabricating transparent paper from cellulose nanofibers (CNFs) normally involves high energy or the use of expensive chemicals for the extraction of CNFs from cellulose fibers and time-consuming paper formation processes because of the slow filtration rate of CNFs. In this study, we reported a strategy for the fabrication of transparent paper using microfibrillated cellulose fibers (MFCFs), which were prepared by extracting nanosized fibrils from the cellulose fiber surfaces by a two-step refining process. The paper made from MFCFs has hierarchical structures of microsized fiber/nanosized fibril networks, where the microsized fiber skeletons are buried in the nanosized fibril networks. Consequently, the paper shows a light transmittance of 82.4% at 550 nm; this is comparable to the light transmittance (89.1%) of papers made from CNFs. Meanwhile, the filtration time of the paper made from MFCFs is less than 2 min, which is much shorter than the time (longer than 180 min) required for the formation of nanopaper made from commercial CNFs. In addition, the transparent paper made from MFCFs shows higher thermal stability, higher tensile strength, higher resistance to deformation, and more flexibility than the nanopaper made from commercial CNFs. This work provides a promising method for the manufacture of transparent paper from cellulose fibers.

Feasibility Study of Chemical Treatments on Sorghum Fibres for Compatibility Enhancement in Polypropylene Composites

Polypropylene (PP) is one of the biggest petro-polymers, which is used in very wide application nowadays. The environment problem due to materials such as plastics having very long time degradability, and critical petroleum sources have promoted some studies to empowerment of natural resources such as natural fibres for substituting or at least modifying petro-polymers. Because of biodegradability obtained from natural source, sorghum fibers are interesting to be used as filler in PP composites, despite of weak compatibility between them. Surface modification on the sorghum fibers through alkalinization prior to acetylation was aimed to improve the fiber compatibility to PP. The treatments were expected to substitute hydroxyl group in the sorghum fibers, into acetic ester group in order to increase their hydrophobicity as the fillers. Moreover, the treatments were able to unbundle single fibers into micro-fibrillated cellulose (MFC) fibres with increase in crystallinity index. Usage of this MFC fiber as filler in PP leads to improvement of the composite performances such as thermal properties. In this study, Fourier Transformation Infra-Red (FTIR) Spectroscopy, X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and Field-Emission Scanning Electron Microscope (FE-SEM) were used to evaluate the performances of the Sorghum fibers after the treatments and as the filler in the Sorghum fibers/PP composites. The experimental results showed the MFC fibers as the smallest sizes in 5.0 microns and the highest crystallinity index up to 79.1 %, obtained from alkalinization with 2.5 M NaOH prior to acetylation with 17.4 M CH3COOH and the glacial (CH3CO2)2. Compatibility study of the treated Sorghum fibers on PP shows an improvement indicated by a strong interaction between the fibers and PP on morphology observation, increase in melting point of PP from 163.4°C (using virgin Shorgum fibers) into 163.6°C (using treated Sorghum fibers) in DSC measurements.

Superheated steam pretreatment of cellulose affects its electrospinnability for microfibrillated cellulose production

In this study, oil palm mesocarp fiber (OPMF) was pretreated with (1) superheated steam (SHS) and (2) potassium hydroxide (KOH) to remove hemicellulose. Both SHS–OPMF and KOH–OPMF underwent delignification step to isolate the cellulose and dissolved in selected ionic liquid and its co-solvent before being electrospun to obtain microfibrillated cellulose (MFC). FE-SEM images showed that SHS–OPMF cellulose produced discontinuous MFC fiber with diameter ranging from 100 to 500 nm, of which 15.5% were in the range of 100–200 nm; while KOH–OPMF cellulose produced continuous MFC with sizes larger than 200 nm. The differences in fiber size and continuity of fiber produced were due to incomplete removal of hemicellulose from SHS–OPMF sample that inhibited fiber re-coalescence and resulted in interruption in fiber formation.

A foldable composite electrode with excellent electrochemical performance using microfibrillated cellulose fibers as a framework

A foldable composite electrode was fabricated for a flexible supercapacitor. The composite possesses not only excellent electrochemical properties, but also structural stability.

Production of Microfibrillated Cellulose by Novel Continuous Steam Explosion Assisted Chemo-Mechanical Methods and Its Characterizations

In this study, microfibrillated cellulose (MFC) was successfully isolated with different time treatments of steam explosion, which were combined with chemo-mechanical stages. The objectives of this study were to isolate and characterize MFC obtained from steam explosion—assisted novel chemo-mechanical methods, and to investigate the effects of different steam explosion times on obtained MFC. Characterizations used were SEM, TEM, PSA, GC–MS, EDS, XRD, FTIR, and STA. The result of this study showed an optimal diameter range of MFC samples was between 23.45 and 77.65 nm at 1 h steam explosion time. However, MFC fibers were aggregated until its particle size distribution by number was about 645.83 nm. That lignocellulose MFC comprised C, N, and O with a dramatic decrease of Si. Most of the samples had many transmittance peaks, indicating the presence of cellulose with –OH, –CH2, C–H, and C–O functional groups whereas IR peaks designated to hemicellulose and lignin were almost absent. The presence of n-heptadecanol-1; n-nonadecanol-1; n-nonadecanol; hexadecanoic acid, ethyl ester; ethyl oleate; and octadecanoic acid, ethyl ester was linked with existance of cellulose and cementing agents (hemicellulose and lignin). There was an increase of cellulose crystallinity along with the increase in steam explosion time. Native cellulose or cellulose I was the initial nature of obtained MFC. The decrease of thermal stability of hemicellulose was correlated with acid treatment and acetyl groups, while the increase of cellulose thermal stability was in accordance with the increase of cellulose crystallinity index.

Alkylation of microfibrillated cellulose – A green and efficient method for use in fiber-reinforced composites

Microfibrillated cellulose (MFC) fibers were alkylated by propargyl bromide, allyl bromide and propyl bromide in an aqueous medium without any stirring. The chemical modifications were confirmed by Fourier transform infrared spectroscopy (FTIR), solid-state 13C nuclear magnetic resonance spectroscopy (NMR) and X-ray photoelectron spectrometry (XPS). The alkylated MFC fibers were obtained with degrees of substitution (DS) ranging from 0.12 to 0.33. All the samples were combined with low-density polyethylene (LDPE), and then the morphology, mechanical properties and water absorption behavior of the ensuing composites were investigated. Study of the morphology of the composites by Scanning Electron Microscopy (SEM) shows a slight improvement of the MFC/LDPE interface after allylation and propargylation. Moreover, the mechanical properties of the composites were significantly improved and the moisture absorption was reduced compared to unmodified MFC fibers.

Characterization of micro-fibrillated cellulose fiber suspension flow using multi scale velocity profile measurements

Characterization of micro-fibrillated cellulose fiber suspension flow using multi scale velocity profile measurements

Using Factorial Design Methodology to Assess PLA-g-Ma and Henequen Microfibrillated Cellulose Content on the Mechanical Properties of Poly(lactic acid) Composites

In this work, a 22 factorial design was used to study the effect of microfibrillated henequen cellulose fibers (HENCEL) and PLA-g-MA coupling agent contents on the tensile, flexural, and impact mechanical properties and the heat deflection temperature (HDT) of biodegradable PLA composites. The results show that the principal effects of HENCEL and MA are statistically significant for the tensile, flexural, HDT, and impact strength properties of PLA composites. Regarding the interactions between the principle effects, MA-HENCEL, there are differences with respect to the mechanical property; for example, for tensile and flexural mechanical properties, there is a synergistic effect between MA and HENCEL, whereas for HDT and impact strength there is not any. The micromechanical analysis shows an excellent agreement between the measured and the estimated values for both the composite tensile strength and the elastic modulus and only slight deviations were noticed for high microfibrillated cellulose fibers content. The morphological analysis via SEM indicated that the addition of PLA-g-MA improved the fiber-matrix adhesion because of the HENCEL unbounding and pull-out decreases from the PLA matrix. The use of appropriate values of matrix strength and stiffness and considering the improved fiber-matrix adhesion of the coupling agent yield a good agreement between experimental and estimated values.

One-Pot Assembly of Microfibrillated Cellulose Reinforced PVA–Borax Hydrogels with Self-Healing and pH-Responsive Properties

A facile, environmentally benign approach has been developed for the preparation of dynamic, multiresponsive, and self-healing hydrogels from inexpensive bamboo pulp, poly(vinyl alcohol) (PVA), and borax. The microfibrillated cellulose (MFC) reinforced PVA–borax hydrogels were produced through a one-pot route in conjunction with ball milling and physical blending in tandem in aqueous medium. In this way, MFC particles could be efficiently generated and well-dispersed in a polymer matrix, and they have been verified by scanning electron microscopy. The rheology analysis indicated a close relationship between the mechanical strength and the MFC loading and ball milling time. Due to the dynamic equilibrium of the didiol–borax linkages and the reinforcement of MFC fibers, the hydrogels showed enhanced self-healing behavior and mechanical stiffness, which was also supported by rheology analyses. In addition, the hydrogels were found to be sensitive to the pH value. The hydrogels present a solvent or gel state ...

Effects of Drying Strategies and Microfibrillated Cellulose Fiber Content on the Properties of Foam-Formed Paper

A novel methodology was used to create a highly porous foam-formed paper that is bonded with highly refined cellulose fiber. In this process, cellulose pulp suspension at various consistencies (0.5, 1.0, 1.5, and 2%) was dispersed in water, followed by foam formation under high shear forces in the presence of a surfactant. Various drying methods were used to achieve foam formation. These included freeze-drying (FD), vacuum-dewatered air-drying (VAD), and dewatered freeze-drying (VFD). Increasing the pulp's consistency and changing the drying techniques from freeze-drying to air-drying resulted in a more compact morphological structure and increased density of foam-formed paper samples. Densification of foam-formed samples was measured using a Dynamic Mechanical Analysis (DMA) machine and a sample with densification at lowest strain value was obtained by a 10 wt% addition of microfibrillated cellulose fiber (MFC). At 10 wt% MFC addition, denser foam-formed paper samples with enhanced microstructure were obtained. Air filtration efficiency and acoustic properties of foam-formed paper were also characterized and optimized by the addition of MFC.

Consolidation and dewatering of a microfibrillated cellulose fiber composite paper in wet pressing

The emerging research field of bio-based nanomaterials has gained a lot of interest recently. One of the most promising new range of materials are the micro and nanofibrillated celluloses, or nanocelluloses that are based on wood or other natural cellulose sources. While the strength increasing potential of nanocelluloses is evident in light of the current knowledge, the related challenges in dewatering are inevitable due to the hydrophilic nature and the large relative surface area of the material. The target of this work was to characterize the dewatering and structural changes of a high filler content (70wt% precipitated calcium carbonate) biocomposite containing microfibrillated cellulose in a wet pressing process. Softwood bleached kraft pulp fibers were used as a reinforcement in the composite. Press dewatering performance together with dynamic density measurements were made with a press simulator, and scanning electron microscopy and mercury intrusion porosimetry were used in the structural analysis of the samples. The dewatering of a new type of MFC based composite was shown to be better than traditional softwood based fibers. The high amount of filler in the structure does not contribute to the binding of water and helps to provide channels for water removal. Mercury porosimetry data was able to partially explain the good press dewatering of the composite paper compared to a SBKP reference paper. Based on the results, it can be concluded that the dewatering of the MFC composite is not limited by the wet pressing operation commonly used in the paper manufacturing industry. Excellent optical properties together with potential cost savings supports the use of this type of novel composite in future applications.