Showing papers on "Fiber published in 2013"

Cellulose Nanocrystals vs. Cellulose Nanofibrils: A Comparative Study on Their Microstructures and Effects as Polymer Reinforcing Agents

Abstract: Both cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) are nanoscale cellulose fibers that have shown reinforcing effects in polymer nanocomposites. CNCs and CNFs are different in shape, size and composition. This study systematically compared their morphologies, crystalline structure, dispersion properties in polyethylene oxide (PEO) matrix, interactions with matrix, and the resulting reinforcing effects on the matrix polymer. Transparent PEO/CNC and PEO/CNF nanocomposites comprising up to 10 wt % nanofibers were obtained via solution casting. Scanning electron microscopy (SEM), wide-angle X-ray diffraction (WXRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analyzer (DMA), and tensile testing were used to examine the above-mentioned properties of nanocellulose fibers and composites. At the same nanocellulose concentration, CNFs led to higher strength and modulus than did CNCs due to CNFs’ larger aspect ratio and fiber entangleme...

Wet-spinning of PEDOT:PSS/Functionalized-SWNTs Composite: a Facile Route Toward Production of Strong and Highly Conducting Multifunctional Fibers

Abstract: With the aim of fabricating multifunctional fibers with enhanced mechanical properties, electrical conductivity and electrochemical performance, we develop wet-spinning of composite formulation based on functionalized PEG-SWNT and PEDOT:PSS. The method of addition and loading are directly correlated to the quality and the ease of spinnability of the formulation and to the mechanical and electrical properties of the resultant fibers. Both the fiber modulus (Y) and strength (σ) scaled linearly with PEG-SWNT volume fraction (Vf). A remarkable reinforcement rate of dY/dVf = 417 GPa and dσ/dVf = 4 GPa were obtained when PEG-SWNTs at Vf ≤ 0.02. Further increase of PEG-SWNTs loading (i.e. up to Vf 0.12) resulted in further enhancements up to 22.8 GPa and 254 MPa in Modulus and ultimate stress, respectively. We also show the enhancement of electrochemical supercapacitor performance of composite fibers. These outstanding mechanical, electrical and electrochemical performances place these fibers among the best performing multifunctional composite fibers.

Mechanical property evaluation of sisal–jute–glass fiber reinforced polyester composites

Abstract: The composite materials are replacing the traditional materials, because of its superior properties such as high tensile strength, low thermal expansion, high strength to weight ratio. The developments of new materials are on the anvil and are growing day by day. Natural fiber composites such as sisal and jute polymer composites became more attractive due to their high specific strength, lightweight and biodegradability. Mixing of natural fiber with Glass-Fiber Reinforced Polymers (GFRPs) are finding increased applications. In this study, sisal–jute–glass fiber reinforced polyester composites is developed and their mechanical properties such as tensile strength, flexural strength and impact strength are evaluated. The interfacial properties, internal cracks and internal structure of the fractured surfaces are evaluated by using Scanning Electron Microscope (SEM). The results indicated that the incorporation of sisal–jute fiber with GFRP can improve the properties and used as a alternate material for glass fiber reinforced polymer composites.

Tin Anode for Sodium-Ion Batteries Using Natural Wood Fiber as a Mechanical Buffer and Electrolyte Reservoir

Abstract: Sodium (Na)-ion batteries offer an attractive option for low cost grid scale storage due to the abundance of Na. Tin (Sn) is touted as a high capacity anode for Na-ion batteries with a high theoretical capacity of 847 mAh/g, but it has several limitations such as large volume expansion with cycling, slow kinetics, and unstable solid electrolyte interphase (SEI) formation. In this article, we demonstrate that an anode consisting of a Sn thin film deposited on a hierarchical wood fiber substrate simultaneously addresses all the challenges associated with Sn anodes. The soft nature of wood fibers effectively releases the mechanical stresses associated with the sodiation process, and the mesoporous structure functions as an electrolyte reservoir that allows for ion transport through the outer and inner surface of the fiber. These properties are confirmed experimentally and computationally. A stable cycling performance of 400 cycles with an initial capacity of 339 mAh/g is demonstrated; a significant improvement over other reported Sn nanostructures. The soft and mesoporous wood fiber substrate can be utilized as a new platform for low cost Na-ion batteries.

Coaxial fiber supercapacitor using all-carbon material electrodes.

Abstract: We report a coaxial fiber supercapacitor, which consists of carbon microfiber bundles coated with multiwalled carbon nanotubes as a core electrode and carbon nanofiber paper as an outer electrode. The ratio of electrode volumes was determined by a half-cell test of each electrode. The capacitance reached 6.3 mF cm–1 (86.8 mF cm–2) at a core electrode diameter of 230 μm and the measured energy density was 0.7 μWh cm–1 (9.8 μWh cm–2) at a power density of 13.7 μW cm–1 (189.4 μW cm–2), which were much higher than the previous reports. The change in the cyclic voltammetry characteristics was negligible at 180° bending, with excellent cycling performance. The high capacitance, high energy density, and power density of the coaxial fiber supercapacitor are attributed to not only high effective surface area due to its coaxial structure and bundle of the core electrode, but also all-carbon materials electrodes which have high conductivity. Our coaxial fiber supercapacitor can promote the development of textile ele...

Study on the mechanical properties and thermal properties of jute and banana fiber reinforced epoxy hybrid composites

Abstract: The aim of the present study is to investigate and compare the mechanical and thermal properties of raw jute and banana fiber reinforced epoxy hybrid composites. To improve the mechanical properties, jute fiber was hybridized with banana fiber. The jute and banana fibers were prepared with various weight ratios (100/0, 75/25, 50/50, 25/75 and 0/100) and then incorporated into the epoxy matrix by moulding technique to form composites. The tensile, flexural, impact, thermal and water absorption tests were carried out using hybrid composite samples. This study shows that addition of banana fiber in jute/epoxy composites of up to 50% by weight results in increasing the mechanical and thermal properties and decreasing the moisture absorption property. Morphological analysis was carried out to observe fracture behavior and fiber pull-out of the samples using scanning electron microscope.

Scalable One‐Step Wet‐Spinning of Graphene Fibers and Yarns from Liquid Crystalline Dispersions of Graphene Oxide: Towards Multifunctional Textiles

Abstract: Key points in the formation of liquid crystalline (LC) dispersions of graphene oxide (GO) and their processability via wet-spinning to produce long lengths of micrometer-dimensional fibers and yarns are addressed. Based on rheological and polarized optical microscopy investigations, a rational relation between GO sheet size and polydispersity, concentration, liquid crystallinity, and spinnability is proposed, leading to an understanding of lyotropic LC behavior and fiber spinnability. The knowledge gained from the straightforward formulation of LC GO “inks” in a range of processable concentrations enables the spinning of continuous conducting, strong, and robust fibers at concentrations as low as 0.075 wt%, eliminating the need for relatively concentrated spinning dope dispersions. The dilute LC GO dispersion is proven to be suitable for fiber spinning using a number of coagulation strategies, including non-solvent precipitation, dispersion destabilization, ionic cross-linking, and polyelectrolyte complexation. One-step continuous spinning of graphene fibers and yarns is introduced for the first time by in situ spinning of LC GO in basic coagulation baths (i.e., NaOH or KOH), eliminating the need for post-treatment processes. The thermal conductivity of these graphene fibers is found to be much higher than polycrystalline graphite and other types of 3D carbon based materials.

Integrated power fiber for energy conversion and storage

Abstract: A new type of integrated power fiber that incorporates a dye-sensitized solar cell (DSSC) and a supercapacitor (SC), which can be used for energy conversation and storage, was introduced for the first time. A stainless steel wire coated with polyaniline via anodic deposition is jointly used as the electrode of the fiber DSSC and fiber SC. The overall energy conversion efficiency of the integrated power fiber is as high as 2.1%. Compared with traditional integrated power systems, our integrated power fiber is lightweight, flexible, inexpensive, suitable for special applications, and capable of integrating with cloth.

Novel electric double-layer capacitor with a coaxial fiber structure.

Abstract: A coaxial electric double-layer capacitor fiber is developed from the aligned carbon nanotube fiber and sheet, which functions as two electrodes with a polymer gel sandwiched between them. The unique coaxial structure enables a rapid transportation of ions between the two electrodes with a high electrochemical performance. These energy storage fibers are also flexible and stretchable, and can be woven into and widely used for electronic textiles.

Natural cellulose fiber as substrate for supercapacitor.

Abstract: Cellulose fiberswithporousstructureandelectrolyte absorption properties are considered to be a good potential substrate for the deposition of energy material for energy storage devices. Unlike traditional substrates, such as gold or stainless steel, paper prepared from cellulose fibers in this study not only functions as a substrate with large surface area but also acts as an interior electrolyte reservoir, where electrolyte can be absorbed much in the cellulose fibers and is ready to diffuse into an energy storage material. We demonstrated the value of this internal electrolyte reservoir by comparing a series of hierarchical hybrid supercapacitor electrodes based on homemade cellulose paper or polyester textile integrated with carbon nanotubes (CNTs) by simple solution dip and electrodeposited with MnO2. Atomic layer deposition of Al2O3 onto the fiber surface was used to limit electrolyte absorption into the fibers for comparison. Configurations designed with different numbers of ion diffusion pathways were compared to show that cellulose fibers in paper can act as a good interior electrolyte reservoir and provide an effective pathway for ion transport facilitation. Further optimization using an additional CNT coating resulted in an electrode of paper/CNTs/MnO2/CNTs, which has dual ion diffusion and electron transfer pathways and demonstrated superior supercapacitive performance. This paper highlights the merits of the mesoporous cellulose fibers as substrates for supercapacitor electrodes, in which the water-swelling effect of the cellulose fibers can absorb electrolyte, and the mesoporous internal structure of the fibers can provide channels for ions to diffuse to the electrochemical energy storage materials.

The effect of fiber morphology on the tensile strength of natural fibers

Abstract: In the present work the morphology of natural fibers was correlated with their mechanical properties via image analysis. Jute, sisal, curaua, coir and piassava fibers were tested under direct tension in a universal testing machine and the cross-sectional areas of the fibers were calculated using images obtained in a scanning electron microscopy. For the jute fiber the tests were performed for several gage lengths in order to investigate its influence on the tensile strength and to compute the machine compliance. For sisal, jute and curaua fibers the amount of fiber-cells, the size of the cell walls and the real area of the fibers were measured and their correlation with the tensile strength addressed. The curaua fiber presented the highest mechanical performance with tensile strength and Young’s modulus of 543 MPa and 63.7 GPa, respectively. Weibull statistical analysis was used to quantify the variability of fiber strength. The sisal fibers presented the highest Weibull modulus (3.70), whereas the curaua presented the lowest one (m = 2.2), which means that the sisal had the lowest variability and curaua the highest.

Tensile and thermomechanical properties of short carbon fiber reinforced polyamide 6 composites

Abstract: In this study, carbon fiber (CF) reinforced polyamide 6 (PA6) composites were prepared by using melt mixing method. Effects of fiber length and content, on the mechanical, thermal and morphological properties of CF reinforced PA6 composites were investigated. Fiber length distributions of composites were also determined by using an image analyzing program. It was seen that the maximum number of fibers were observed in the range of 0–50 μm. Mechanical test results showed that, increasing CF content increased the tensile strength, modulus and hardness values but decreased strain at break values of composites. DSC results showed that Tg and Tm values of composites were not changed significantly with increasing CF content and length. However, heat of fusion and the relative degree of crystallinity values of composites decreased with ascending CF content. DMA results revealed that storage modulus and loss modulus values of composites increased with increasing CF content.

Effects of Working Parameters on Electrospinning

Abstract: Working parameters are very important to understand not only the nature of electrospinning but also the conversion of polymer solutions into nanofibers through electrospinning. Those parameters can be broadly divided into three parts such as solution parameters, process parameters, and ambient parameters. Each of those parameters can affect the fibers morphologies and by proper control of those parameters we can fabricate electrospun fibers with desired morphologies and diameters. In this chapter, we will present a concise introduction of those parameters and their influence on fiber properties.

Thermal Conductivity of High-Modulus Polymer Fibers

Abstract: Polymers have many desirable properties for engineering systems–e.g., low mass density, chemical stability, and high strength-to-mass ratio–but applications of polymers in situations where heat transfer is critical are often limited by low thermal conductivity. Here, we leverage the enormous research and development efforts that have been invested in the production of high-modulus polymer fibers to advance understanding of the mechanisms for thermal transport in this class of materials. Time-domain thermoreflectance (TDTR) enables direct measurements of the axial thermal conductivity of a single polymer fiber over a wide temperature range, 80 < T < 600 K. Relaxation of thermoelastic stress in the Al film transducer has to be taken into account in the analysis of the TDTR data when the laser spot size is small because the radial modulus of the fiber is small. This stress relaxation is controlled by the velocity of the zero-order symmetric Lamb mode of a thin Al plate. We find similarly high thermal conduct...

Effect of polypropylene fiber on durability of concrete composite containing fly ash and silica fume

Abstract: A parametric experimental study has been conducted to investigate the effect of polypropylene fiber on the workability and durability of the concrete composite containing fly ash and silica fume. Four different fiber volume fractions (0.06%, 0.08%, 0.1% and 0.12%) were used. The results indicate that the addition of polypropylene fiber has a little adverse effect on the workability of concrete composite containing fly ash and silica fume. With the increase of fiber volume fraction, both of the slump and slump flow are decreasing gradually. However, the addition of polypropylene fiber has greatly improved the durability of the concrete composite containing fly ash and silica fume. The length of water permeability, the dry shrinkage strain and the carbonation depth of concrete containing fly ash and silica fume are decreasing gradually with the increase of fiber volume fraction as the fiber volume fraction is below 0.12%. Besides, freeze–thaw resistance of polypropylene fiber reinforced concrete containing fly ash and silica fume was found to slightly increase when compared to the concrete composite without fibers. Moreover, there is a tendency of increase in the freeze–thaw resistance with the increase of fiber volume fraction as the fiber volume fraction is below 0.08%. However, the freeze–thaw resistance begins to decrease slightly after the fiber volume fraction beyond 0.08%.

Prepreg and carbon fiber reinforced composite material

Abstract: Disclosed is a prepreg containing a carbon fiber [A] and a thermosetting resin [B], while satisfying at least one of the following conditions (1) and (2). (1) A thermoplastic particle or fiber [C] and a conductive particle or fiber [D] are contained, and the weight ratio represented by [the blended amount of [C] (parts by weight)]/[the blended amount of [D] (parts by weight)] is 1-1000. (2) A conductive particle or fiber [E], which is obtained by coating a nucleus or core of a thermoplastic resin with a conductive material, is contained.

Transparent nanopaper with tailored optical properties.

Abstract: Nanopaper is a flexible, transparent, and renewable substrate that is emerging as a replacement for plastic in printed "green" electronics. The underlying science of transparency of nanopaper is that the diameter of these fibers is much smaller than the light wavelength, which significantly decreases the light scattering as compared to regular fibers. Cellulose fibers have a hierarchical structure, which consists of numerous smaller fibers. In this manuscript, we demonstrate a nanopaper design with different fiber diameters, and conclude that the light transmittance and scattering depend on the fiber diameter and packing density. The optical properties of the nanopaper and their dependence on the cellulose fiber diameter are thoroughly explained through Chandrasekhar's radiative-transfer theory and multiple scattering method simulations. The controllable optical properties of highly transparent nanopaper present an unprecedented opportunity for growth of next-generation optoelectronics.