Microfibrillated Cellulose Research Articles

Upscaled engineered functional microfibrillated cellulose flat sheet membranes for removing charged water pollutants

Polymeric composite membranes have shown great potential in removing pollutants from water. In the current study, flat sheet functional membranes of microfibrillated cellulose (MFC) with mixed and layered architectures are produced using the up-scaled Dynamic Sheet Former (Formette) in a fully water-based-system, and their potential for the removal of charged impurities is evaluated. The processing of composite membranes is unique in terms of their size (1 m × 20 cm), assembled MFC architectures, controlled/tunable porosity, functional groups densities, and free-standing at high water pressure. Such properties could be difficult to achieve with a lab-scale processing setup. It is shown that the MFC assembly has a direct influence on the pollutant removal efficiency, and again the layered architecture turns out to be a more efficient scavenger of the charged pollutants due to the combined actions of electrostatic interactions, hydrogen bonding, and size exclusion, which are responsible for an ultrafast separation of the impurities through the flat sheets membranes. These experimental results are supported by reactive molecular dynamics simulations of representative model systems that provided possible realistic scenarios at the atomic/molecular scale. All the data confirm the scalability and tunability of the produced MFC-based water cleaning membranes, which show high adsorption capacity, flexibility, hydrolytic stability, and mechanical robustness. SynopsisResults of this article could be easily implemented for the removal of charged pollutants from water for effective biobased filter development.

Atomization of Microfibrillated Cellulose and Its Incorporation into Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Reactive Extrusion

The present study focuses on the preparation and characterization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films that were reinforced with cellulose microstructures to obtain new green composite materials for sustainable food packaging applications. The atomization of suspensions of microfibrillated cellulose (MFC) successfully allowed the formation of ultrathin cellulose structures of nearly 3 µm that were, thereafter, melt-mixed at 2.5, 5, and 10 wt % with PHBV and subsequently processed into films by thermo-compression. The most optimal results were attained for the intermediate MFC content of 5 wt %, however, the cellulose microstructures showed a low interfacial adhesion with the biopolyester matrix. Thus, two reactive compatibilizers were explored in order to improve the properties of the green composites, namely the multi-functional epoxy-based styrene-acrylic oligomer (ESAO) and the combination of triglycidyl isocyanurate (TGIC) with dicumyl peroxide (DCP). The chemical, optical, morphological, thermal, mechanical, and barrier properties against water and aroma vapors and oxygen were analyzed in order to determine the potential application of these green composite films in food packaging. The results showed that the incorporation of MFC yielded contact transparent films, whereas the reactive extrusion with TGIC and DCP led to green composites with enhanced thermal stability, mechanical strength and ductility, and barrier performance to aroma vapor and oxygen. In particular, this compatibilized green composite film was thermally stable up to ~280 °C, whereas it showed an elastic modulus (E) of above 3 GPa and a deformation at break (ɛb) of 1.4%. Moreover, compared with neat PHBV, its barrier performance to limonene vapor and oxygen was nearly improved by nine and two times, respectively.

Microfibrillated cellulose-enhanced carboxymethyl chitosan/oxidized starch sponge for chronic diabetic wound repair

Herein, a novel microfibrillated cellulose (MFC) reinforced natural polymer-based sponge composed of carboxymethyl chitosan (CMC) and oxidized starch (OS) with hemostatic, repairing-promoting, and antimicrobial performances was fabricated for chronic wound repair. When the content of MFC reached 1.2 wt%, the prepared sponge exhibited ultra-fast water or blood-trigged shape recovery property within 3 s. Moreover, sponge was functionally modified with silver nanoparticles (AgNPs) and recombinant humanized collagen type III (rhCol III). The AgNPs and rhCol III loaded sponge (A-Ag/III) could effectively kill a broad spectrum of pathogenic microbes, promote the proliferation and migration of L929 cells in vitro. Due to their erythrocyte-aggregating ability and positive-charge feature of CMC, the A-Ag/III displayed rapid hemostasis ability. Furthermore, the in vivo animal experiment demonstrated the A-Ag/III could promote wound repair by inhibiting inflammation, promoting angiogenesis, and cell proliferation.

Durable Activated Carbon Electrodes with a Green Binder

Herein, the fabrication and electrochemical performance of thick (180−280 μm) activated carbon (AC) electrodes with carbonized lignin‐derived carbon fiber (LCF) inclusions are reported. Efforts are taken in fabricating robust free‐standing electrodes from an environmentally friendly binder, microfibrillated cellulose (MFC), considering the biologically hazardous nature of other commonly used binders like polytetrafluoroethylene (PTFE), n‐methyl‐2‐pyrrolidone (NMP), and polyvinylidene fluoride (PVDF). Generally, electrodes composed of MFC binder are prone to cracking upon drying, especially with higher mass loadings, which leads to nonflexibility and poor device stability. The LCF inclusions into the AC electrode with MFC binders not only increase flexibility but also contribute to better conductivity in the electrodes. The LCFs act as an intermediate layer among AC particles and serve as conductive pathways, facilitating exposure of more active surfaces to the electrolyte. A thick electrode with high mass loading of 10 mg cm−2 is achieved. The results show that by incorporating 2 wt% LCF to the AC material, the best device with 5 mg cm−2 delivers a specific capacitance of 97 F g−1, while the specific capacitance of the reference AC device without LCF is 85 F g−1.

A comparative study of the effects of pulp fractionation, refining, and microfibrillated cellulose addition on tissue paper properties

Environmental and economic concerns are driving tissue paper manufacturers to improve understanding of the relationships between fibres, the networks they form, the forming process, and the final tissue paper properties. This work investigated how pulp fractionation, refining, or addition of microfibrillated cellulose (MFC) affect the compromise between absorbency and strength of 33 ± 2 g/m² model papers made of bleached eucalyptus kraft pulp. The results showed that the compromise of properties was better when fibres were refined than when MFC was added. The absorbency capacity of 2%wt MFC-paper was almost 20% lower than the capacity of the refined paper at the same dry strength. The calculated additional storage capacity due to water-induced deformations of the fibre network was 40% lower in the same range of bulk. By forming a high viscosity gel at inter-fibre contacts, MFC could limit the occurrence of major fibre and network deformation mechanisms when water was imbibing the paper.

Effect of gelatin type on the structure and properties of microfibrillated cellulose reinforced gelatin edible films

AbstractThe physical and mechanical properties of gelatin edible films need to be significantly improved to meet the increasing requirements of food and pharmaceutical industry. This study investigates the effect of gelatin type on the structure and properties of glycerol plasticized gelatin films reinforced by microfibrillated cellulose (MFC). Results indicate that the tensile strength of type‐A and type‐B gelatin (GelA and GelB) films increases by 48% and 90% respectively at an optimum MFC content of 15 wt% in comparison to control gelatin films without MFC. The incorporation of MFC also has a more pronounced impact on optical properties and moisture absorption capability of GelB films than on those of GelA films. Scanning electron microscopy and polarized optical microscopy studies show that the MFC fibrils are uniformly distributed in both types of gelatin matrices. X‐ray diffraction and attenuated total reflectance‐Fourier transform infrared analyses reveal that the interactions between MFC and GelB are stronger than those of between the MFC and GelA. The mechanism behind the more significant mechanical performance improvement of GelB films by the addition of MFC is speculated to be that stronger hydrogen bonding interactions contribute to enhanced structural integrity and stability of the gelatin‐based films.

Biobased Composites by Photoinduced Polymerization of Cardanol Methacrylate with Microfibrillated Cellulose.

Biobased monomers and green processes are key to producing sustainable materials. Cardanol, an aromatic compound obtained from cashew nut shells, may be conveniently functionalized, e.g., with epoxy or (meth)acrylate groups, to replace petroleum-based monomers. Photoinduced polymerization is recognized as a sustainable process, less energy intensive than thermal curing; however, cardanol-based UV-cured polymers have relatively low thermomechanical properties, making them mostly suitable as reactive diluents or in non-structural applications such as coatings. It is therefore convenient to combine them with biobased reinforcements, such as microfibrillated cellulose (MFC), to obtain composites with good mechanical properties. In this work a cardanol-based methacrylate monomer was photopolymerized in the presence of MFC to yield self-standing, flexible, and relatively transparent films with high thermal stability. The polymerization process was completed within few minutes even in the presence of filler, and the cellulosic filler was not affected by the photopolymerization process.

Evaluating 3D-printability of polyvinyl alcohol (PVA) and microfibrillated cellulose (MFC) composite inks

Polyvinyl alcohol (PVA) is a popular material due to its water solubility and tunable mechanical properties. However, because of its low yield stress in an aqueous solution, PVA is not directly printable using direct ink writing (DIW) 3D printing. To overcome this challenge, this study explored a simple approach of blending PVA with non-chemically modified microfibrillated cellulose (MFC) to form a printable ink for DIW printing. PVA (9.1, 11.1, 13.1 wt%) and MFC (1, 2, and 3 wt%) were mixed to formulate inks with nine different compositions. The printability of the nine inks was evaluated for (1) filament width, (2) printability factor, and (3) stackability of inks in layers. Based on the qualitative analysis of printed structures and evaluation of the print area, the ink compositions of 11.1/2,13.1/2, 9.1/3, and 11.1/3 (denoted as PVA%/MFC%) were selected for further evaluation. Alternatively, the printability factor suggested the compositions of 9.1/2, 9.1/3, and 11.1/3 offered good printability. Finally, the ink of 11.1/2 was used to demonstrate the potential of the PVA/MFC composite ink for DIW 3D printing by stacking 100 layers in a cage structure. This work paves the way to develop sustainable solutions to create DIW-printed structures consisting of PVA and biocompatible additives for various applications, including tissue engineering, packaging, and filtration.

Effect of epoxidation levels on curing characteristic and mechanical properties of ENR/MFC composites

This study aimed to investigate the effect of epoxidation levels on the curing and tensile properties of epoxidized natural rubber (ENR)/microfibrillated cellulose (MFC) composites. ENRs with different levels of epoxidation were first prepared from natural rubber (NR) latex via ‘in situ’ performic epoxidation using 0.75 M formic acid and 1 M hydrogen peroxide at 50°C at various reaction times. The results from H1 NMR revealed that the reaction at 2, 4, and 6 hours could achieve 20, 30, and 40 mol % epoxidation, respectively. The introduction of epoxide groups into NR chains reduced the scorch and cure time along with the increase of the epoxy content. Furthermore, it was observed that the tensile strength rose remarkably at 30 mol% epoxidation (ENR30). Therefore, the ENR30 was subsequently chosen to prepare the composites with various amounts of MFC (1, 3, and 5 parts per hundred rubber, phr). Interestingly, incorporating MFC elevated tensile strength and elongation at break of ENR30. At 5 phr of MFC, the composite possessed the highest tensile strength and elongation at break value, which reached up to 31.07 MPa and 922.92%, respectively.

Biocomposites of Polylactic Acid Reinforced by DL-Lactic Acid-Grafted Microfibrillated Cellulose

Microfibrillated cellulose (MFC) is often added to polylactic acid (PLA) matrixes as a reinforcing filler to obtain fully-biodegradable composites with improved mechanical properties. However, the incompatibility between MFC and the PLA matrix limits the mechanical performance of MFC-reinforced PLA composites. In this paper, DL-lactic acid-grafted-MFC (MFC-g-DL) was used to improve the compatibility with PLA. Reinforced composites were prepared by melt extrusion and hot-cold pressing. The tensile strength of the PLA/MFC-g-DL composite increased by 22.1% compared with that of PLA after adding 1% MFC-g-DL. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and dynamic thermomechanical analysis (DMA) were used to explore the enhancement mechanism. The energy dissipation in the MFC network and the improved compatibility between PLA and MFC-g-DL played important roles in the reinforcement. The SEM results showed that there was a closer combination between PLA and MFC-g-DL. The DSC results showed that the addition of cellulose changed the glass transition temperature, melting temperature, and crystallization temperature of PLA. The TG results showed that the initial and maximum decomposition temperature were lower than those of PLA. The ultraviolet spectra showed that the composite had good transparency at a low concentration of MFC-g-DL.

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.

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.

Chemo-enzymatic functionalized sustainable cellulosic membranes: Impact of regional selectivity on ions capture and antifouling behavior

Most of the polymeric membranes synthesized for decentralization of polluted water use fossil-based components. Thus, there is an urgent need to create robust and tunable nano/micro materials for confidently designing efficient and selective polymeric water filters with guaranteed sustainability. We have chosen a robust high-grade microfibrillated cellulose (MFC) as the functional material and selectively tuned it via enzymatic catalysis, which led to the attachment of phosphate group at the C6 position, followed by esterification (fatty acid attachment at C2 and C3 carbon), which led to the increase in its antifouling properties. We have demonstrated the robustness of the functionalization by measuring the separation of various metal ions, and the antifouling properties by adding foulants, such as Bovine Serum Albumin (BSA) and cancerous cells to the test solutions. These prototype affinity MFC membranes represent the most promising type of next-generation high-performance filtration devices for a more sustainable society.

Electroassisted Filtration of Microfibrillated Cellulose: Insights Gained from Experimental and Simulation Studies

An electroassisted filtration technique has been employed to improve dewatering of a suspension of microfibrillated cellulose (MFC) produced via 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation. In addition, all-atom molecular dynamic (MD) simulations were performed to deepen the understanding of the complicated dewatering mechanism on a molecular level. Both the experimental and the simulation results implied that the dewatering rate was not only improved when electroassisted filtration was used but also found to be proportional to the strength of the electric field. A channeled dewatered structure was observed for these experiments and may have contributed to enhanced dewatering by providing high overall permeability. The MD simulations revealed that the electric field had a significant impact on the fibril movement, whereas the impact of pressure was limited. The simulations also suggested that the increased filtrate flow upon the application of an electric field was not only due to electroosmotic flow but also due to electrophoretic movement of the fibrils toward the anode that led to the release of water that had been trapped between the fibrils, allowing it to be pressed out together with the rest of the bulk water. This study shows that electroassisted filtration has the potential to improve the dewatering of TEMPO-MFC, and the MD simulations provide further insights into the dewatering mechanism.

Microfibrillated Cellulose Grafted with Metacrylic Acid as a Modifier in Poly(3-hydroxybutyrate)

This work proposes a new method for obtaining poly(3-hydroxybutyrate) (PHB)/microfibrillated cellulose (MC) composites with more balanced properties intended for the substitution of petroleum-based polymers in packaging and engineering applications. To achieve this, the MC surface was adjusted by a new chemical route to enhance its compatibility with the PHB matrix: (i) creating active sites on the surface of MC with γ-methacryloxypropyltrimethoxysilane (SIMA) or vinyltriethoxysilane (SIV), followed by (ii) the graft polymerization of methacrylic acid (MA). The high efficiency of the SIMA-MA treatment and the lower efficiency in the case of SIV-MA were proven by the changes observed in the Fourier transform infrared FTIR spectra of celluloses. All modified celluloses and the PHB composites containing them showed good thermal stability close to the processing temperature of PHB. SIMA-modified celluloses acted as nucleating agents in PHB, increasing its crystallinity and favoring the formation of smaller spherulites. A uniform dispersion of SIMA-modified celluloses in PHB as a result of the good compatibility between the two phases was observed by scanning electron microscopy and many agglomerations of fibers in the composite with unmodified MC. The dual role of SIMA-MA treatment, as both compatibilizer and plasticizer, was pointed out by mechanical and rheological measurements. This new method to modify MC and obtain PHB/MC composites with more balanced stiffness–toughness properties could be a solution to the high brittleness and poor processability of PHB-based materials.

Active and Robust Composite Films Based on Gelatin and Gallic Acid Integrated with Microfibrillated Cellulose.

Background: Gelatin is a renewable, biodegradable, and inexpensive food polymer. The insufficient mechanical and functional properties of gelatin-based films (GBF) restrict their commercial application in food packaging. This work proposed a facile strategy to prepare an active and robust GBF that has the potential to be used in food packaging. Methods: A strong and active GBF was prepared based on the principle of supramolecular chemistry via the incorporation of gallic acid (GA) as an active crosslinking agent and of microfibrillated cellulose (MFC) as a reinforcing agent. Results: Under the appropriate concentration (1.0 wt%), MFC was evenly dispersed in a gelatin matrix to endow the film with low surface roughness and compact structure. Compared with the GF, the tensile strength and elongation at break of the resultant film reached 6.09 MPa and 213.4%, respectively, representing the corresponding improvement of 12.8% and 27.6%. Besides, a significantly improved water vapor barrier (from 3.985 × 10−8 to 3.894 × 10−8 g·m−1·Pa−1·s−1) and antioxidant activity (from 54.6% to 86.4% for ABTS radical scavenging activity; from 6.0% to 89.1% for DPPH radical scavenging activity) of GBFs were also observed after introducing the aromatic structure of GA and nano-/microfibrils in MFC. Moreover, the UV blocking performance and thermal stability of GGF and GGCFs were also enhanced. Conclusions: this work paves a promising way toward facile preparation of multifunctional GBFs that have great potential to be used in fabricating active and safe food packaging materials for food preservation.

Rapid Screening of Microfibrillated Cellulose Tructure Through FTIR and Principal Component Analsysis

Analysis of FTIR spectra combined with multivariate statistical analysis technique specifically Principal Component Analysis was used for rapid screening of microfibrillated cellulose (MFC) structure. The current methods used to extract the MFC are by using the chemical and physical approaches. To date, most researchers focused on bench (lab) scale experiment to identify the structure of MFC. Lack of mathematical models focusing on this goal has motivated this project. Principal component analysis is applied to identify the chemical composition of the MFC. The dataset comprises FTIR spectra of 12 samples that comes from MFC with different particles sizes, 200 µm, 250 µm and 800 µm. The result shows that the wavelength region which represents the MFC structure is in the range of 2950 cm-1 to 2978 cm-1 for particle size of 200 micrometer since it has larger surface area for penetration of fungal into the biomass due to lower diffusion of air, water and metabolite intermediates of which cellulose can be easily hydrolyzed due to increase in pore size of substance through greater removal of hemicellulose and lignin. The overall result indicates that the combination of FTIR analysis and PCA is a useful technique for rapid screening of MFC structure.

High-yield, high-conductive graphene/nanocellulose hybrids prepared by Co-exfoliation of low-oxidized expanded graphite and microfibrillated cellulose

Nowadays, high performance and functional low-dimensional nanomaterials have been targeted in modern sustainable energy science for diverse potential applications. However, broad applications of emerging nanomaterials such as graphene and biomass nanofillers have suffered from low preparation efficiency, low quality of products, unstable dispersion in matrix. In this study, a 100% yield of low-oxidized graphene/nanocellulose hybrids (LGENC) was prepared by one-pot ball milling. Low-oxidized expanded graphite (LOEG) and microfibrillated cellulose (MFC) were used as precursors for fabricating LGENC by the co-exfoliation strategy. That is, exfoliation of LOEG, nanofibrillation of MFC and their hybridization were simultaneously realized under the shear and collision of balls milling. The concentration of LGENC suspension can be concentrated to 50 mg/mL, which has great potential for 3D printing. A series of characterization identified the hybridization of low-oxidized graphene (LGE) and nanocellulose via hydrophobic and hydrogen bond interaction, and confirmed that the LGE has fewer oxygen functional groups and more complete structure than graphene oxide. Benefiting from the intact structure, the conductivity of LGENC can reach up to ~5800 S/m. In addition, the as-prepared LGENC showed significant potential in reinforcing rubber latex. In general, this study proposes a high-efficiency preparation method for graphene/cellulose hybrid materials with extraordinary properties.

Cassava starch-chitosan-sorghum micro-fibrillated cellulose biocomposite wrapping film to prevent COVID-19 outspread

To prevent virus spreading, the corpse or the coffin of COVID-19 patients need to be wrapped in plastic. Low-density polyethylene (LDPE), a crude oil-based wrapping plastic, is difficult to decompose in nature after use. In this study, biocomposite wrapping film was developed from cassava starch and chitosan, with the addition of sorghum Micro-Fibrillated Cellulose (MFC) by levels of 1%, 2%, 3%, 4% and 5%. Cassava starch (raw starch) was modified by acetic anhydride to produce acetylated cassava starch (acetylated starch) which is less hydrophilic thus enhance the compounding ability with LDPE. The sorghum MFC was obtained from sorghum fibers after following processes: soda pulping, bleaching and fibrillation with a super grinder. The addition of 1% sorghum MFC into raw starch-chitosan increased the tensile strength and modulus of elasticity by 33% and 17%, respectively. On the other hand, the addition of 2% sorghum MFC into acetylated starch-chitosan increased the elongation by 38%. Wrapping film needs to have good elongation ability so that it can be stretched during application. Based on elongation characteristic, acetylated cassava starch-chitosan with addition of 2% sorghum MFC can be developed to be a candidate for biocomposite wrapping film to prevent COVID-19 outspread.

A comparative investigation of gelatinized and regenerated starch composites reinforced by microfibrillated cellulose

This research demonstrated a novel and ecofriendly method for producing regenerated starch (RS)/microfibrillated cellulose (MFC) composite films with a nearly 1.4-fold improvement in tensile strength than traditional gelatinized starch (GS) films. Pure starch was dissolved in 14 wt% urea/4 wt% sodium hydroxide (NaOH) solution at 0 °C. Then, RS films and their biocomposite films containing MFC were prepared by dialyzing and solution-casting method. Results showed that the tensile strength and elongation at break of RS increased by 44.8% and 82.4%, compared with that of GS film, respectively. Owing to the adequate dispersion, lower viscosity-average molecular weight, higher amylose content, lower crystallinity and smaller crystal grain size, RS/MFC composite films exhibited significantly improved mechanical properties. The novel strategy used in this study will be helpful in preparing regenerated starch materials with excellent mechanical properties and biodegradability as alternatives to petrochemical plastics for the development of sustainable materials.