Cellulose Whiskers Research Articles

Modified Cellulose Proton-Exchange Membranes for Direct Methanol Fuel Cells.

A direct methanol fuel cell (DMFC) is an excellent energy device in which direct conversion of methanol to energy occurs, resulting in a high energy conversion rate. For DMFCs, fluoropolymer copolymers are considered excellent proton-exchange membranes (PEMs). However, the high cost and high methanol permeability of commercial membranes are major obstacles to overcome in achieving higher performance in DMFCs. Novel developments have focused on various reliable materials to decrease costs and enhance DMFC performance. From this perspective, cellulose-based materials have been effectively considered as polymers and additives with multiple concepts to develop PEMs for DMFCs. In this review, we have extensively discussed the advances and utilization of cost-effective cellulose materials (microcrystalline cellulose, nanocrystalline cellulose, cellulose whiskers, cellulose nanofibers, and cellulose acetate) as PEMs for DMFCs. By adding cellulose or cellulose derivatives alone or into the PEM matrix, the performance of DMFCs is attained progressively. To understand the impact of different structures and compositions of cellulose-containing PEMs, they have been classified as functionalized cellulose, grafted cellulose, acid-doped cellulose, cellulose blended with different polymers, and composites with inorganic additives.

DEM and dual-probability-Brownian motion scheme for thermal conductivity of multiphase granular materials with densely packed non-spherical particles and soft interphase networks

Shape-anisotropic granules and their surrounding interphase networks are significant constituents in granular materials. Structural and physical configurations of these constituents significantly affect the overall thermal performance of granular materials, specifically microstructure-dependent thermal conductive properties. It has been a key but unresolved issue how to quantitatively understand the microstructure evolution of conductive interphase interacted by densely packed non-spherical particles triggering the change of thermal conductivity of granular materials. In this work, we devise a powerful scheme by using the discrete element method (DEM) and the dual-probability-Brownian motion simulation (DP-BMS) to accurately and efficiently predict the effective thermal conductivity of granular materials composed of homogeneous matrix, conductive (soft) interphase around randomly-dispersed elliptical particles over a broad range of aspect ratios with widespread applications, such as cracks, pores, fibers, cellulose whiskers, silicate nanorods, and aggregates. Comparison against extensive numerical and theoretical data validates that such the scheme can well predict the effective thermal conductivity of multiphase granular materials with densely packed non-spherical particles that is just the intrinsic limitation of the classical micromechanical homogenization theories. In this scheme, the DEM provides a direct means of investigating the time-dependent microstructure evolution of granular materials with elliptical particles from a loose parking state to a dense packing state. The DP-BMS provides an effective technique for predicting the effective thermal conductive transport properties of multiphase granular materials. By comparing with traditional numerical strategies like the finite element method (FEM) and random walk model (RWM), the DP-BMS is more user-friendly and efficient to accurately predict the effective thermal conductivity. This scheme can be regarded as a general procedure that is readily applicable to predictions of other transport properties of two-dimensional or three-dimensional multiphase granular materials. Furthermore, we use the scheme to probe the influences of the shape and high packing density of particles and the thickness and fraction of soft interphase on the effective thermal conductivity of granular materials. The results elucidate rigorous component-structure–property relations, which can provide sound guidance for composite design and microstructure optimization.

Properties of cellulose reinforced composites: A review

This paper provides a review of cellulose, sources, extraction, molecular structure, cellulose whiskers, preparations, and morphology. The mechanical and thermal properties of cellulose reinforced composites are also discussed. Detail structure of Nano whiskers is also reported. As a renewable biomaterial, the most common source of cellulose is the plant. These plants include fruit fibers (coir), seed fibers (cotton), wood, leaf fibers (sisal), bast fibers (jute, kenaf, and hemp). Other sources of cellulose are from micro-organisms such as fungi, tunicates, bacteria, and algae. Cellulose whiskers are isolated from cellulose fibers by acid hydrolysis. Cellulose micro fibril structures are made of both amorphous and crystalline regions. The amorphous regions are vulnerable to hydrolysis by acids compared to the crystalline domains. Several techniques among which are Field Emission Scanning Electron Microscopy (FESEM), Transmission electron microscopy (TEM) and Atomic Force Microscopy (AFM) have been used to study the morphology of cellulose whiskers. An interface between cellulose whisker and matrix is a transition zone between the matrix and the cellulose whiskers. It plays an important role in the overall mechanical properties of the composites. A soft interface domain will yield a greater resistance to fracture, while the composite will be low in stiffness and strength. On the other hand, a stiffer interface domain may cause the composite to be strong and stiff and less resistant to fracture. The addition of CW into polymers matrices has little or no effect on the glass transition temperature, (Tg) except on the modification of CW.
 Keywords: Cellulose, whiskers, mechanical, thermal, properties, biomaterials

Morphological and performance characteristics of nanocomposite films based on poly(lactic acid) compounded with nanocrystalline cellulose and chitin whiskers using melt extrusion

The purpose of this work was to evaluate the morphological, mechanical, barrier and phase-transition properties of poly(lactic acid) (PLA) films with nanofillers such as nanocrystalline cellulose (NCC, 1–5%) and chitin whiskers (CHW, 3%). Nanofiller addition using melt extrusion led to decrease in heat capacity change at glass transition as observed from differential scanning calorimetry data. Transmission electron microscopy and x-ray diffraction studies showed that the nanofillers were dispersed in the polymer matrix. This indicated confinement of the motion of polymer chains between layers of nanofillers. Tensile strength (TS) of PLA-based nanocomposite films increased from 50.2 to 70.9 MPa with addition of 5% NCC to PLA. However, addition of CHW did not significantly improve TS. Addition of 3% NCC reduced oxygen transmission rate of films from 209.9 to 180.8 cm3/m2/day, which further reduced to 109.3 cm3/m2/day by adding compatibilizer, methylene diphenyl diisocyanate (MDI, 4%). Water vapor transmission rate of PLA reduced from 44.4 to 28.6 g/m2/day with 3% NCC and 4% MDI addition. This research suggested the promising application of NCC as a nanofiller in PLA films with enhanced thermal, mechanical and barrier properties, and potential application in bio-based food packaging.

Preparation and Properties of Nano Coir Cellulose Whiskers Enhanced CS/PVA Composite Film

Nano coir cellulose whiskersare materials abstracted from mesocarp of coconut shell which was modified by using KH570 as a coupling agent and modified nano coir cellulose whiskers need to be dispersed in chitosan/polyvinyl alcohol (CS/PVA) mixture solution. Because of regular structure and high crystallinity, nano coir cellulose whiskers could be applied in medical materials.In this paper, the results obtained with solution casting method by characterizing and analyzing structure, thermal properties, crystallization behavior and morphology of nano coir cellulose whiskers enhanced CS/PVA composite filmby FTIR, DSC, TG, XRD and SEM test. Different content of modified nano coir whiskers and CS/PVA composite film were preparedand themechanical properties of the composite film were also conducted. The results show that the tensile strength and Young's modulus of the CS/PVA composite film with modified nano coir whiskers are significantly improved, and Elongation break increases at first and then decreases, which indicates nano coir cellulose whiskers are good materials for medical purpose.

Utilization of Areca Nut Leaf Sheath Fibers for the Extraction of Cellulose Whiskers

ABSTRACT In this study, cellulose whiskers were extracted from an agricultural plant waste, Areca Nut Leaf Sheath, by employing a sulfuric acid hydrolysis method. The effect of hydrolysis time and temperature on the morphology, crystallinity, and degree of polymerization of the resultant cellulose particles was studied. Highly crystalline cellulose whiskers with an aspect ratio around 20 were obtained under moderate conditions of hydrolysis by maintaining the temperature at 45°C and hydrolysis time of 180 min. However, on increasing the temperature and time of hydrolysis, surface flattening of fibers was observed and aspect ratio was decreased. Isolated cellulose whiskers were found to contain traces of biosilica.

Cellulose Whiskers Derived from Banana Pseudo-Stem as Potential Reinforcement Filler for Tyre Tread Compounds

In this study, cellulose fibre was extracted from banana pseudo-stem and converted into cellulose whiskers (CWs) with high-pressure defibrillation method. The CWs were characterized using FTIR, XRD and the results conform the structure of cellulose. XRD studies showed that the percentage crystallinity of bleached fibres is about 93%. The particle size analysis showed a bimodal distribution for CWs where approximately 21% of the sample has average size of 110 nm. The rubber compounds were prepared according to a general tyre tread formulation while incorporating the purified CWs in diluted centrifuged latex (NR) followed by converting them into rubber sheets to produce cellulose whiskers/natural rubber CW/NR composite. Meanwhile, the control was prepared without incorporating CW in the diluted centrifuged latex. The lowest Mooney viscosity and the highest stress relaxation coefficient of CW/NR composites ensured higher processability. Curing characteristics of the compounds were evaluated at 120 °C and physical properties were evaluated on par to the ASTM standards. The highest cure rate and better scorch time were observed in CW/NR composite. Most of the physical properties were superior. In overall, it is obvious that cellulose whiskers have a potential to use as reinforcing material for natural rubber tyre tread compounds.

Morphological, barrier and mechanical properties of films from poly (butylene succinate) reinforced with nanocrystalline cellulose and chitin whiskers using melt extrusion

Nanocomposites from biodegradable poly (butylene succinate) (PBS), blended with nanofillers chitin whiskers (CHW, 1–5%) and nanocrystalline cellulose (NCC, 1–5%), were synthesized using melt extrusion. Morphological studies using transmission electron microscopy showed the dispersion of nanofillers in the polymer matrix. The nanofillers restricted the mobility of polymer chains, and promoted nucleation and recrystallization of polymer as reflected by increase in degree of crystallinity (Xc) from 65.9 to 75.6%. Addition of NCC and CHW increased the tensile strength of PBS based films from 23.2 MPa to 32.9 MPa and 43.6 MPa, respectively. Decrease in oxygen transmission rate of PBS films from 737.7 to 280 cc/m2/day was observed by adding 3% NCC, which further reduced to 23.8 cc/m2/day by adding compatibilizer methylene diphenyl diisocyanate (MDI, 4%). Water vapor transmission rate of PBS films reduced from 83.8 to 49.4 g/m2/day with 3% NCC addition and addition of 4% MDI further reduced it to 30.8 g/m2/day. This research suggested potential of NCC and CHW as nanofillers for enhancement of mechanical and barrier properties of PBS based films used in biodegradable food packaging applications.

Bio-inspired amino-acid-functionalized cellulose whiskers incorporated into sulfonated polysulfone for proton exchange membrane

Proton exchange membranes with remarkable performance are important for the development of direct methanol fuel cells. Inspired by the proton-conducting mechanism of transmembrane proteins, amino-acid-functionalized cellulose whiskers, are developed as a novel proton-conducting pathway for hybrid proton exchange membranes. Fmoc-amino acids are immobilized onto the surface of cellulose whiskers to obtain amino acids (Glycine, 5-amino-Valeric acid, l-Serine, l-Asparagine, and l-Leucine) functionalized cellulose whiskers with primary amino groups after Fmoc-deprotection. Proton-conducting mixed-matrix membranes are obtained by incorporating amino-acid-functionalized cellulose whiskers into sulfonated polysulfone. The performance of hybrid proton exchange membranes is evaluated to study the effects of the structure and content of amino acids. Results shows that the introduction of amino acids considerably enhances the proton conductivity. Proton exchange membranes with 4 wt.% and 10 wt.% content of l-Serine-functionalized cellulose whiskers have high proton conductivity of 0.209 S/cm and 0.234 S/cm at 80 °C, respectively. In addition, water uptake, resistance to methanol permeability and single-cell performance are also enhanced. These results indicates that the composition of filler and mixed matrix exhibit remarkable properties, and proton-conducting mixed-matrix membranes are promising materials in direct methanol fuel cells.

Improvement of water quality of remnant from chemical retting of coconut fibre through electrocoagulation and activated carbon treatment

Remnant obtained from chemical retting of coconut fibre was found to have an exorbitant COD, BOD, TDS, sulphide content having blackish brown colour. Traditional (physico-chemical) treatment could not reduce its COD, TDS, colour substantially. Further, the traditional method was lengthy, consumed huge chemicals and time. Present paper reports a quicker, simpler, economic i.e., an industrially viable method to separate the chemicals and biomass by employing electrocoagulation (EC). The performance of EC was analyzed by keeping temperature, and pH of remnant constant, while varying current flow (100–2000 mA), time (15–90 min) and number of iron electrodes (2,4,6). Efficacy of EC was evaluated in terms of reduction in conductivity, pH, TDS, COD, TOC, colour and quantity of sludge generated from the wastewater. Six electrodes with 2000 mA current flow for 90 min were found to give noticeable reduction on COD (92.8%), TOC (56%), TDS (99%), and colour. To reduce pH, and TDS to an acceptable level, filtration with activated charcoal was attempted on recovered water from EC. Resultant water was also found to have acceptable LC50 value for safe disposal. Carbon content (53%) in the sludge was high, contained lignin and cellulose whiskers also, as revealed from the EDX and FTIR, SEM respectively. Cost of EC ($ 0.087 USD/L) was found to be much less as compared to traditional method ($ 0.384 USD/L).

Cellulose Whiskers Influence the Morphology and Antibacterial Properties of Silver Nanoparticles Composites.

Cellulose, the main component of plant cell walls, is a biopolymer widely used for industrial applications, including, food, paper and textile fabrication. More recently, hybrid materials composed of cellulose nanostructures and metal nanoparticles have been applied in diverse areas such as medical and pharmaceutical applications. In this work, cellulose-silver nanoparticles (AgNPs) hybrid material was synthesized and the influence of cellulose, employed as a stabilizer agent, was investigated. Specifically, cellulose whiskers (CCW) were extracted from commercial cotton fibers by acid hydrolysis route, while the AgNPs were synthesized by reducing silver salt using sodium citrate and/or sodium borohydride in the presence of CCW. The synthesized AgNPs/CCW nanocomposites were characterized in terms of morphology, chemical composition, surface charge and antibacterial properties. The varied synthetic routes generated AgNPs with different morphological characteristics in terms of size, shape and coalescence. The particularity of each sample resulted in distinct behaviors for the tested bacteria. Syntheses employing CCW resulted in AgNPs/CCW nanocomposites with controlled morphology and improved antibacterial effects against E. coli (Gram-negative) and S. aureus (Gram-positive), indicating CCW as a promising compound to be used in the syntheses of silver and other metal nanoparticles with controlled morphology and antibacterial properties.

Water‐induced mechanically adaptive behavior of carboxylated acrylonitrile‐butadiene rubber reinforced by bacterial cellulose whiskers

Water‐induced mechanically adaptive rubber nanocomposites were prepared by mixing bacterial cellulose whiskers (BCWs) suspension with carboxylated acerlonitrile‐butadiene rubber (XNBR) latex, followed by latex blending method. The introduction of BCWs into XNBR enhanced the tensile storage modulus (E') significantly, which originated from the formation of a rigid 3D filler network within matrix as well as the interfacial interaction between filler and matrix. The water uptake ratio of nanocomposite films increased with BCWs content, from 5.5% for neat XNBR to 54% for nanocomposite with 20 phr (parts per hundred rubber) BCWs. Upon submersed in water, the nanocomposite films showed dramatic decrease in E′, especially for which filled with high BCWs loadings. For example, E′ of nanocomposite with 20 phr BCWs was decreased by 98.04% after equilibrium swelling compared with only 52.02% for nanocomposite with 3 phr BCWs. The remarkable water‐triggered modulus changes are attributed to the disentanglement of BCWs network after swelling. The prepared XNBR–BCWs nanocomposites with mechanically adaptive properties could contribute to develop the new type of rubber‐based smart materials. POLYM. ENG. SCI., 59:58–65, 2019. © 2018 Society of Plastics Engineers

Water-induced modulus changes of bio-based uncured nanocomposite film based on natural rubber and bacterial cellulose nanocrystals

Bacterial cellulose whiskers (BCWs) were firstly incorporated into natural rubber (NR) by an evaporation method. The structure, morphology, dynamic mechanical properties, water uptake and water-responsive behavior of modulus for NR/BCWs nanocomposite films were investigated. It was found that the hydrophilic BCWs generated a significant reinforcement effect on the storage modulus of NR. In the presence of water, the nanocomposite films showed a pronounced response in storage modulus, especially for the nanocomposite filled with highest filler content. The storage modulus of films with 20 phr (parts per hundred rubber) BCWs decreased by 95.3% after equilibrium swelling in water. This modulus change behavior was attributed to the disentanglement of hydrophilic filler network via competitive hydrogen bonding with water. NR/BCWs nanocomposite film could be used as a new type of shape-memory material for biomedical applications.

Stimuli‐responsive polymer nanocomposites based on styrene‐butadiene rubber and bacterial cellulose whiskers

Water‐induced mechanically adaptive rubber nanocomposites were prepared by mixing bacterial cellulose whiskers (BCWs) suspension with styrene‐butadiene rubber (SBR) latex, followed by evaporation method. The structure, morphology, dynamic mechanical properties, water stimuli‐responsive behavior, and biodegradability of SBR/BCWs nanocomposite films were investigated. The results showed that the hydrophilic whiskers had a significant reinforcement effect on the storage modulus of SBR matrix, which originated from the formation of a rigid three‐dimensional filler network within matrix by strong hydrogen bonding between whiskers. The SBR/BCWs nanocomposites showed pronounced water stimuli‐responsive behavior compared with neat SBR. The storage modulus of SBR/BCWs nanocomposite could be decreased by 99.2% after equilibrium water swelling. This remarkable water‐triggered modulus change is attributed to the disentanglement of BCWs network via competitive hydrogen bonding with water.

Preparation and characterization of poly(ethylene 2,5-furandicarboxylate/nanocrystalline cellulose composites via solvent casting

Abstract The effect of nanocrystalline cellulose dispersion on the nonisothermal crystallization of poly(ethylene 2,5-furandicarboxylate) (PEF) has been investigated by means of solvent casting. The cellulose dispersion plays a significant role on the crystallization temperature, thus dispersive equipments of increasing energies were employed to improve the cellulose particles disaggregation. Therefore, ultra-sonic bath, ultra-sonication, and ultra-turrax were used to disperse cellulose nanocrystals in 1,1,1,3,3,3-hexafluoro-2-propanol. Dissolved separately in the same solvent, PEF was then poured into the cellulose suspension before casting. The cellulose whiskers were inspected by transmission electron microscopy. Differential scanning calorimetry was used to measure the crystallization temperature, while scanning electron microscopy visualized the cellulose dispersion at the fracture surface. After investigation on the interaction of cellulose/PEF via Fourier transform infrared spectroscopy, the thermal stability of the blends was measured by means of thermogravimetric analysis.

A transparent wound dressing based on bacterial cellulose whisker and poly(2-hydroxyethyl methacrylate)

The current study was aimed to develop a transparent wound dressing comprised of bacterial cellulose (BC) and poly (2-hydroxyethyl methacrylate) (PHEMA) hydrogel coated with silver (Ag) nanoparticles. Briefly, different concentrations of BC whiskers (BCWs) were added into the HEMA solution to form PHEMA/BCWs hydrogel with volume ratio of monomer HEMA and BCWs as 7:3 and 1:1. The addition of BCWs into PHEMA matrix improved its equilibrium water content and light transmittance about 20%-40% and 10%, respectively. The Young's modulus for PHEMA was found to be 0.72MPa, which was improved to 0.57MPa and 0.50MPa for PHEMA/BCWs 7:3 and PHEMA/BCWs 1:1, respectively. Further, immersion of PHEMA/BCWs hydrogel in the AgNO3 and NaBH4 solutions bestowed it with antibacterial property and produced inhibition zones of 0.5±0.15cm and 0.25±0.15cm against Escherichia coli and Staphylococcus aureus, respectively. Similarly, PHEMA/BCWs prepared with 0.001M AgNO3 and 0.001M NaBH4 solutions showed 99% and 90% reduction in colony forming unit (CFU) for E. coli and S. aureus, respectively, after 24h. The PHEMA/BCWs/Ag hydrogel facilitated the growth of NIH3T3 fibroblast, showing their low toxicity. These results demonstrate the suitability of PHEMA/BCWs/Ag hydrogel for its application as potential transparent wound dressing material for skin repair.

A facile method to prepare cellulose whiskers–silica aerogel composites

Highly porous and hydrophobic cellulose whiskers–silica aerogel composites were successfully fabricated by a novel co-precursor method based on sol–gel process under ambient pressure drying. Cellulose whiskers were dispersed in the initial sol and were finally inlaid in silica aerogel skeleton by physical combination, which retained the integrality of the aerogel matrix. With the increase of cellulose whiskers content from 0 to 15%, the volume shrinkage of alcogels during drying process decreased from 25.5 to 17.6%, while the porous nano-structure of aerogels were not significantly altered. The potential impact of cellulose whiskers on the thermal conductivity and thermal stability of the prepared composites was investigated. The new composite was intact and white, which exhibited typical properties of 0.137 g cm−3 density, 3.525 cm3 g−1 pore volume, and 139.6° contact angle, respectively. This work explained how the addition of an organic filler into the silica aerogels influenced their properties and provided a technique for silica aerogels to endure and remain monolithic under ambient pressure drying.

Enhanced mechanical properties of styrene–butadiene rubber with low content of bacterial cellulose nanowhiskers

AbstractStyrene–butadiene rubber (SBR) nano‐composites were prepared through mixing SBR latex with bacterial cellulose whiskers (BCWs). BCWs were extracted from the residual bacterial cellulose (BC) that was treated with acid hydrolysis. A rod‐like nanofiber structure of BCWs was observed by transmission electron microscopy and atomic force microscopy. BCWs maintained the crystal structure in BCWs/SBR nano‐composites as confirmed by X‐ray diffraction patterns. The dispersion of BCWs in SBR matrix was further detected with field emission scan electron microscope. BCWs acted as a multifunctional physical cross‐linker in the SBR matrix, the combination of BCW reinforcement and increased effective cross‐linking density of the rubber network with incorporating BCWs would cause a more effective transfer of stresses from matrix to filler. Compared with neat SBR, the tensile strength and tear strength of SBR/BCW nano‐composite with 2.5 phr (parts per hundred rubber) BCWs were increased by 319% and 182%, respectively.

Thermal characteristics of polyethylene oxide and functionalized bacterial cellulose whisker nanoparticle composite nanofibers

Composite nanofibers of polyethylene oxide (PEO)/bacterial cellulose whisker nanoparticles (BCW NPs) and PEO/functionalized bacterial cellulose whisker nanoparticles (f-BCW NPs) were fabricated by an electrospinning process. BCW NPs were prepared using a blender in order to increase the filler density in composite nanofibers. Nitrogen functionalization of the f-BCW NPs was performed by plasma treatment using a microwave oven. The chemical bonding between the nitrogen functional groups of f-BCW NPs and the hydroxyl groups of the polymer chains in the PEO matrix was enhanced by the nitrogen functionalization. The average diameter of the PEO/f-BCW NP composite nanofibers was slightly larger than that of PEO nanofibers and PEO/BCW NP composite nanofibers at the same concentration. The melting temperature (T m), crystallization temperature (T c), and weight loss of PEO/f-BCW NP composite nanofibers decreased compared to those of the PEO nanofibers and PEO/BCW NP composite nanofibers. This was a result of the f-BCW NPs hindering the crystallization of the PEO nanofiber structures. The strong interfacial interactions between the f-BCW NP nanofillers and the polymer matrix increased the glass transition temperature (T g) compared to PEO nanofibers and PEO/BCW NP composite nanofibers. These results demonstrated that N2 plasma treatment of BCW NPs embedded in PEO nanofiber was a useful tool for improving their thermal characteristics for biological applications.

Isoniazid loaded gelatin-cellulose whiskers nanoparticles for controlled drug delivery applications

Natural polymers like gelatin have been used as a potential drug carrier for controlled delivery applications due to their various advantages over synthetic polymers. Cellulose Whiskers (CWs) have the capacity to form strong hydrogen bonds which help in controlling the release of drug and also provide good strength to the drug carrier. In this report, CWs were prepared from filter paper cellulose by acid hydrolysis. Also, attempt was made to prepare gelatin-CWs nanoparticles by desolvation method using an anti-tuberculosis drug, isoniazid and a crosslinker glutaraldehyde (GA). The CWs and gelatin-CWs nanoparticles were characterized by X-ray diffractometry (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The effect of CWs on gelatin nanoparticles over 8-hour period was measured in swelling studies. Efficiency of drug loading and subsequent release of isoniazid in buffer solutions at pH 1.2 (0.1N HCl) and pH 7.4 (phosphate buffer) were studied. Cytotoxicity study showed less toxicity for gelatin-CWs nanoparticles.