Hollow Fiber Composites Research Articles

Development of Hollow Fiber Membranes Functionalized with Ionic Liquids for Enhanced CO2 Separation.

The combination of CO2-selective ionic liquids (ILs) with block copolymers, such as Pebax 1657, has demonstrated an enhancement of the gas separation capabilities of polymeric membranes. In the current work, the development of composite membranes by applying a thin, concentrated selective layer made of Pebax/imidazolium-based ionic liquids (ILs) is presented. The objective of the experiments was to determine the optimized IL loading and investigate how the alteration of the anion impacts the properties of the membranes. Two membrane configurations have been studied: coated flat sheet membranes, supported on a porous poly(ether sulfone) (PES) layer, as well as composite hollow fiber membranes, supported on commercial polypropylene (PP) hollow fibers. Coated hollow fiber composites were fabricated using a continuous coating method, offering a straightforward scalability in the manufacturing process. The determined mechanical pressure stability of hollow fiber composites reached up to 5 bar, indicating their potential for various industrial gas separation applications. It was found that the Pebax 1657-based coating containing 40 wt % [C6mim][NTf2] yielded membranes with the best gas separation properties, for both the coated flat sheet and the hollow fiber configurations. The CO2 permeance of hollow fibers reached 23.29 GPU, whereas the CO2/N2 ideal selectivity stood at 8.7, suggesting the necessity of the further enhancement of the coating technique, which can be achieved, for example, through application of multiple coatings. Nonetheless, the superior ideal selectivity of the CO2/CO separation, reaching 12.44, gave a promising outlook for further novel membrane applications, which involve the separation of the aforementioned gases.

Hollow Co9S8-carbon fiber hierarchical heterojunction with Schottky contacts for tunable microwave absorption

Heterogeneous interface engineering of hollow hierarchical structures with Schottky contacts is an attractive approach for designing light weight and efficient microwave absorption (MA) materials. Herein, hollow Co9S8-carbon fiber (CF) composites were prepared by solvothermal, electrostatic spinning, and pyrolysis methods. CF was used as the main chain and hollow Co9S8 derived from metal-organic frameworks (MOFs) was homogeneously embedded in it, which overcame the difficulties of the traditional template method and effectively avoided the particle agglomeration problem. The interface polarization relaxation process is improved by the construction of Co9S8-CF heterojunction with Schottky contacts, which effectively modulates the dielectric loss. The internal hollow macroporous cavity and CF with lightweight properties enhance the reflection attenuation of the internal cavity. In addition, the electromagnetic characteristics can be flexibly adjusted to achieve the tunable MA performance by varying the reaction parameters. As a result, the Co9S8-CF-3–700 exhibits optimum MA performance, with a reflection loss (RL) of −60.83 dB at 10.85 GHz and a thickness of 2.76 mm. The effective absorption bandwidth (EAB) extends to 5.6 GHz at a thickness of 2.19 mm. This research provides a promising approach to creating light weight and efficient MA materials with potential applications in radar and communication systems.

Enhancement of bursting pressure resistance of braid-reinforced polyether sulfone hollow fiber composites

Enhancement of bursting pressure resistance of braid-reinforced polyether sulfone hollow fiber composites

Double-Loss Co-Ti3C2Tx/Fe2O3/PAN Hollow Fiber Composite Material for High-Efficiency Electromagnetic Absorption

Electromagnetic absorbing materials (EMAs) are materials that irreversibly convert electromagnetic waves into another type of energy. With the development of communication technology, electromagnetic absorption materials have broad prospects in smart phones, wearable devices, and aerospace. MXenes have excellent dielectric loss properties, and the synthesis and application of MXene functional materials with magnetic properties will be one of the hotspots and focuses of future research. In this study, magnetic Co-Ti3C2Tx MXenes were prepared by molten salt etching, and Co-Ti3C2Tx/Fe2O3/polyacrylonitrile (PAN) hollow fiber composites with double-loss capability were prepared by coaxial electrospinning technology. The maximum reflection loss of the Co-Ti3C2Tx/Fe2O3/PAN hollow fiber can reach −54.62 dB at 9.86 GHz, and the effective absorption bandwidth is 6.39 GHz. The Co-Ti3C2Tx/Fe2O3/PAN hollow fibers with excellent electromagnetic absorption capability exhibit potential for efficient EMA materials due to their synergistic effect of impedance matching and magnetic/dielectric loss.

Clustering Effect on the Frequency-Dependent Magnetic Properties of Fe–Co Micro Hollow Fiber Composites

Composite sheets including Fe–Co magnetic hollow fibers are applicable to near-field electromagnetic wave absorption sheets operating in excess of 1 GHz. To understand the frequency-dependent permeability behavior of composite sheets, the Landau–Lifshitz–Gilbert equation and effective medium theory which are including the effects of the eddy current losses of isolated fibers and magnetostatic correction in high volume fractions can be used. However, the simulation considering only these factors requires a very high damping factor to explain the measured results. Thus, the simulation also needs the consideration of the clustering effect of particles causing the additional eddy current losses. In this paper, a new simulation method for magnetic sheets with clustered particles is proposed to improve an understanding of changes in the high-frequency properties of magnetic composite sheets due to the clustering effect.

Mechanical behavior of MWCNTs based mixed-matrix polymeric and carbon hollow fiber membranes

Abstract The effect of multi-wall carbon nanotubes (MWCNTs) addition in co-polyimide Hollow Fiber Membranes (HFMs) on their mechanical behavior was investigated. BTDA-TDI/MDI (P84) co-polyimide hollow fiber membranes, both single phase and composites, were prepared by wet spinning process via phase inversion technique. Phenol-functionalized MWCNTs were used as filler material into the polymer matrix, while carbon HFMs (CHFMs) were produced by controlled pyrolysis. MWCNTs addition significantly increased tensile and flexural modulus of elasticity of the HFMs. A linear increase of ultimate tensile strength along with the filler concentration reflects the good MWCNTs dispersion in the HFMs. This tensile and flexural strength increase was also followed by an increase in helium and nitrogen permeances as well as by a decrease in tensile ductility. The transition of the polymeric to the carbon phase resulted in a dramatic increase in modulus of elasticity and a linear correlation between ultimate tensile strength and filler concentration was also observed. The mechanical test results and the effect of the filler concentration are discussed by taking into account the gas permeance performance of the investigated membranes.

Experimental and theoretical investigation of hollow polyester fibers effect on impact behavior of composites

In this paper, the effect of utilizing hollow polyester fibers as reinforcement in composite material in comparison with solids is investigated. The three-point bending impact test is carried out to study the impact behavior and mode of failure of composites. After that, the finite element method is used for theoretical investigation and modeling the behavior of two different reinforced composites during impact tests. It was found that the fiber–matrix interface failure is the most dominant mode of failure and the crack was initiated at the middle of the bottom surface of composites. It was also found that the impact resistance of the hollow fiber composite is more than the others. Theoretical results showed good correlation with experimental results as well. The stress distribution and the maximum value of strain energy density was found as two factors which lead to improvement in the impact behavior of hollow fiber composites.

Oxygen separation membrane based on facilitated transport using cobalt tetraphenylporphyrin-coated hollow fiber composites

The post-combustion flue gas discharged from coal-fired power plants is a major source of carbon dioxide, which contributes to global warming. Oxygen in post-combustion flue gas causes oxidative degradation of the amine-based solvents used in the carbon capture process. In this study, a cobalt tetraphenylporphyrin mediated facilitated transport membrane is considered for flue gas pretreatment. It is possible to exactly characterize the membrane by various microscopic and spectroscopic techniques. The results show that the hollow fiber is evenly coated as a thin dense layer with an increasing packing density. Gas permeation test shows that the oxygen/nitrogen and oxygen/carbon dioxide selectivity values reach 2.8 and 1.5, respectively, with an oxygen permeance of 53GPU at 0.05bar. It is expected that, because of the oxygen facilitated transport behavior, the membrane system will be able to remove oxygen from post-combustion flue gas using the current membrane for flue gas pretreatment, retarding the degradation of the absorbent.

Aminosilane-Grafted Zirconia-Titiania-Silica Nanoparticles/Torlon Hollow Fiber Composites for CO2 Capture.

In this work, the development of novel binary and ternary oxide/Torlon hollow fiber composites comprising zirconia, titania, and silica as amine supports was demonstrated. The resulting binary (Zr-Si/PAI-HF, Ti-Si/PAI-HF) and ternary (Zr-Ti-Si/PAI-HF) composites were then functionalized with monoamine-, diamine-, and triamine-substituted trialkoxysilanes and were evaluated in CO2 capture. Although the introduction of both Zr and Ti improved the CO2 adsorption capacity relative to that with Si/PAI-HF sorbents, zirconia was found to have a more favorable effect on the CO2 adsorption performance than titania, as previously demonstrated for amine sorbents in the powder form. The Zr-Ti-Si/PAI-HF sample with an oxide content of 20 wt % was found to exhibit a relatively high CO2 capacity, that is, 1.90 mmol g(-1) at atmospheric pressure under dry conditions, owing to more favorable synergy between the metal oxides and CO2 . The ternary fiber sorbent showed improved sorption kinetics and long-term stability in cyclic adsorption/desorption runs.

Electro-magnetic properties of composites with aligned Fe-Co hollow fibers

A novel Fe-Co binary hollow fiber was synthesized by electroless plating using hydrolyzed polyester fiber and its anisotropy characteristic was investigated for electromagnetic wave absorbing materials. The hollow fibers in parallel with magnetic field show higher saturated magnetization of 202 emu/g at the applied magnetic field of 10 kOe and lower coercivity (27.658 Oe), compared with the random and vertical oriented hollow fibers. From complex permittivity measurement, the Fe-Co hollow fiber composites clearly display a single dielectric resonance, located at ∼14 GHz. The Fe-Co hollow fibers not only provide excellent EM properties in GHz frequency ranges, resulting mainly from the strong resonance, but also adjust the soft magnetic properties through fiber alignments. The cavitary structure of the Fe-Co hollow fibers, not only giving rise to a dielectric loss resonance and also adjusting its peak frequency, may be a pathway to useful EM wave absorptive devices in GHz frequency ranges.

Therapeutic-designed electrospun bone scaffolds: Mesoporous bioactive nanocarriers in hollow fiber composites to sequentially deliver dual growth factors

A novel therapeutic design of nanofibrous scaffolds, holding a capacity to load and deliver dual growth factors, that targets bone regeneration is proposed. Mesoporous bioactive glass nanospheres (MBNs) were used as bioactive nanocarriers for long-term delivery of the osteogenic enhancer fibroblast growth factor 18 (FGF18). Furthermore, a core–shell structure of a biopolymer fiber made of polyethylene oxide/polycaprolactone was introduced to load FGF2, another type of cell proliferative and angiogenic growth factor, safely within the core while releasing it more rapidly than FGF18. The prepared MBNs showed enlarged mesopores of about 7nm, with a large surface area and pore volume. The protein-loading capacity of MBNs was as high as 13% when tested using cytochrome C, a model protein. The protein-loaded MBNs were smoothly incorporated within the core of the fiber by electrospinning, while preserving a fibrous morphology. The incorporation of MBNs significantly increased the apatite-forming ability and mechanical properties of the core–shell fibers. The possibility of sequential delivery of two experimental growth factors, FGF2 and FGF18, incorporated either within the core–shell fiber (FGF2) or within MBNs (FGF18), was demonstrated by the use of cytochrome C. In vitro studies using rat mesenchymal stem cells demonstrated the effects of the FGF2–FGF18 loadings: significant stimulation of cell proliferation as well as the induction of alkaline phosphate activity and cellular mineralization. An in vivo study performed on rat calvarium defects for 6weeks demonstrated that FGF2–FGF18-loaded fiber scaffolds had significantly higher bone-forming ability, in terms of bone volume and density. The current design utilizing novel MBN nanocarriers with a core–shell structure aims to release two types of growth factors, FGF2 and FGF18, in a sequential manner, and is considered to provide a promising therapeutic scaffold platform that is effective for bone regeneration.

Improvement of Impact Damage Resistance of Epoxy-Matrix Composites Using Ductile Hollow Fibers

Fiber reinforced polymer structures typically respond very poorly to transverse impact events. In this study, some experimental investigations are performed on the low velocity impact behavior of unidirectional hollow, solid and hybrid (hollow/solid) polyester fiber composites. The materials are fabricated in a curved shape using filament winding method. The impact tests are applied on the simply supported specimens by a drop weight impact test apparatus at five levels of energy. To present a proper comparison on the results, the various densities of the materials are considered as normalizing coefficients. It is observed that in the hollow fiber composites cracks appear at an appreciably higher amount (93%) of impact energy than the solid ones.

Feasibility Study of Microfabrication by Coextrusion (MFCX) Hollow Fibers for Active Composites

Active composites based on a hollow fiber topology have advantages over solid piezoelectric fiber composites in that they require lower voltages for activation and are not limited to electrically non-conductive matrix materials. One critical issue for hollow fiber composites is the fiber aspect ratio (ratio of wall thickness to fiber radius). In this paper analytical and finite element models, which include electric field variations, were developed to determine the “effective d31”of an individual piezoelectric hollow fiber. The effective fiber properties were used to derive a single-row lamina strain/electric field model from classical composite theory. The models were validated with a series of deflection/voltage experiments conducted with hollow piezoelectric fibers fabricated utilizing microfabrication by coextrusion (MFCX) techniques. To determine the feasibility of MFCX hollow fiber composites, the models and experimental results were employed to study the effect of the fiber aspect ratio on a variet...

Feasibility Study of Microfabrication by Coextrusion (MFCX) Hollow Fibers for Active Composites

Active composites based on a hollow fiber topology have advantages over solid piezoelectric fiber composites in that they require lower voltages for activation and are not limited to electrically non-conductive matrix materials. One critical issue for hollow fiber composites is the fiber aspect ratio (ratio of wall thickness to fiber radius). In this paper analytical and finite element models, which include electric field variations, were developed to determine the “effective d31”of an individual piezoelectric hollow fiber. The effective fiber properties were used to derive a single-row lamina strain/electric field model from classical composite theory. The models were validated with a series of deflection/voltage experiments conducted with hollow piezoelectric fibers fabricated utilizing microfabrication by coextrusion (MFCX) techniques. To determine the feasibility of MFCX hollow fiber composites, the models and experimental results were employed to study the effect of the fiber aspect ratio on a variety of fiber/composite design issues: fiber/lamina performance, fiber strength, matrix material, and electric field effects (incomplete poling and field concentrations).