Composite Fibrous Membranes Research Articles

Capillary Action-Inspired Nanoengineering of Spheres-on-Sphere Microspheres with Hollow Core and Hierarchical Shell.

The current syntheses of spheres-on-sphere (SOS) microsphere, which possesses both hollow cavity and hierarchical structure, mainly rely on complicated routes and template removal. In this study, a one pot nanoengineering strategy inspired by the automatic transport behavior of water in plants is successfully developed to fabricate SOS microsphere in tandem with a traditional soft template method in the preparation of hollow structure. Amphiphilic siloxane oligomers generated in situ from methyltriethoxylsilane (MTES) under acidic conditions are anchored on the surface of soft template St monomer droplets, sequentially completing hydrolysis-polycondensation and forming a mesoporous polysilsesquioxane (PSQ) shell. Then, the St monomers located in cavity migrate outward under the combined action of capillary force stemming from mesoporous and osmotic pressure generating from inside-outside of the PSQ shell and polymerize on the outside of the hollow PSQ shell, in which residual siloxane oligomers further anchor on the polystyrene (PS) surface to reduce the surface energy of the system, finally resulting in the successful formation of SOS particles. To reduce thermal insulation coefficient of the material, the PS phase in SOS particles is removed to obtain the particles with multiscale hollow structure (SOS-MH), which have more hollow cavities to encapsulate more air. The presence of a much hollow structure in SOS-MH particles enables the thermal conductivity of polyacrylonitrile (PAN)/SOS-MH composite fibrous membranes (0.0307 W m-1 K-1) to decrease by about 40% compared to that of pure PAN fibrous films (0.0520 W m-1 K-1) at the same thickness of 1 mm, and the material also has moisture resistance due to the existence of a hierarchical shell.

A flexible fibrous membrane based on copper(II) metal-organic framework/poly(lactic acid) composites with superior antibacterial performance.

A flexible antibacterial fibrous membrane employing high antibacterial efficiency has great potential in healthcare applications. Herein, a three-dimensional copper(ii) metal-organic framework [Cu2(CA)(H2O)2, Cu-MOF-1] and poly(lactic acid) (PLA) composite fibrous membrane was prepared through a facile electrospinning method. The sphere-like Cu-MOF-1 was rapidly synthesized by a microwave-assisted hydrothermal reaction of Cu(ii) salts with citric acid (H4CA) in the presence of polyvinyl pyrrolidone (PVP). The surface morphology, thermal stability, mechanical properties and hydrophilicity test of the as-prepared Cu-MOF-1/PLA fibrous membrane were studied systematically. Compared with commercial copper nanoparticles (Cu-NPs), citric acid and copper citrate, Cu-MOF-1 showed higher antibacterial properties with the bacteriostatic rates of 97.9% and 99.3% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively, when the used dose was 250 μg mL-1. The Cu-MOF-1/PLA fibrous membrane also exhibited outstanding bactericidal activities against E. coli and S. aureus with the antibacterial rates up to 99.3% and 99.8%, respectively. Mechanism investigation indicated that the slowly released Cu2+ ions could destroy the microenvironment of bacteria cells and destroy the integrity and permeability of the cell membrane, leading to enzyme inactivation. Therefore, the as-prepared flexible fibrous membrane will advance progress toward developing a broad spectrum antibacterial textile for healthcare protection related applications.

Transport Analysis of Anti-Wetting Composite Fibrous Membranes for Membrane Distillation.

Composite electrospun fibrous membranes are widely studied for the application of membrane distillation. It is an effective approach to enhance the membrane distillation performance in terms of anti-wetting surface and permeate flux by fabricating composite fibrous membranes (CFMs) with a thin skin layer on a thick supporting layer. In this work, various membranes prepared with different pore sizes and porosities by polyacrylonitrile and polyvinylpyrrolidone were prepared. The membrane characteristics and membrane distillation performance were tested. The mass transfer across the membranes was analyzed experimentally and theoretically in detail. It is shown that the skin layer significantly increases liquid entry pressure of the CFM by 5 times. All the membranes have a similar permeate flux. The permeate flux of membranes is stable at 19.2 ± 1.2 kg/m2/h, and the salt rejection ratios remain above 99.98% at 78 ± 1 °C for 11 h. The pore size and porosity of membranes have an insignificant effect on the temperature distribution of membrane. The porosity and pore size of the skin layer have an insignificant effect on the mass transfer process of the CFM. The mass transfer process of the CFM is governed by the supporting layer.

Morphology, physical, and mechanical properties of potentially applicable coelectrospun polysulfone/chitosan‐polyvinylalcohol fibrous membranes in water purification

AbstractPolysulfone (PSU) is a widely used polymer in water purification membranes. However, its hydrophobicity hinders its practical application. Herein, the wettability of PSU has been improved by producing a coelectrospun fibrous composite membrane using a hydrophilic component, chitosan‐polyvinyl alcohol (CS‐PVA). First, different proportions of PVA and CS solutions were mixed and electrospun to prepare CS‐PVA blend fibers. Scanning electron microscope (SEM) observations revealed that CS‐PVA blend fibers with maximum CS content can be obtained in 30:70 CS:PVA weight ratio. The optimum CS‐PVA solution was subsequently used alongside PSU solution and were fed into two distinct syringes, which were then electrospun simultaneously at a constant voltage and distance of 15 kV and 15 cm, respectively. Different composite compositions of PSU/CS‐PVA were achieved using different feeding rates for each solution. Based on SEM images, the prepared composite fibers were beadless. The ultimate strength of the composite mats decreased by increasing the amount of CS‐PVA due to the significant difference in the fiber diameter of each component and the resulting stress concentration. However, the thermal stability of composite membranes remained almost the same as pure PSU fibers. Moreover, samples with higher CS‐PVA content showed better wettability and higher water flux.

Hierarchical porous poly(l-lactic acid)/SiO2 nanoparticles fibrous membranes for oil/water separation

A two-step strategy has been developed to introduce silica nanoparticles into highly porous poly(l-lactic acid) (PLLA) nanofibers. Silica nanoparticles (SiNPs) were firstly synthesized and then modified to be hydrophobic. After PLLA/SiNPs composite fibrous membranes were electrospun and collected, they were re-crystallized by acetone at room temperature for a few minutes. With the re-arrangement of PLLA chains, the nano-/micro-electrospun fibres were transformed from non-porous ones to be porous ones with high surface area. Consequently, SiNPs that were completely covered by PLLA before acetone treatment showed up at the fibre surface. Higher PLLA crystallization also enhanced the Young’s modulus and tensile strength (420 and 8.47 MPa) of the composite membrane. However, incorporation of SiNPs into porous PLLA membranes reduced their modulus and tensile strength (280.66 and 5.92 MPa), but an increase in strain to fracture (80.82%) was observed. Scanning electron microscopy (SEM), focused ion beam SEM, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction were applied to confirm the presence of SiNP in PLLA fibres. The presence of SiNPs inside and outside fibres enhances the hydrophobicity of PLLA/SiNPs nano-fibrous membrane as the water contact angle is greater than 150°. The oil absorption of these porous composite membranes was also tested using four different oils, which can reach the highest absorption capacity when the weight ratio of PLLA and SiNPs is 1:1. The flux of prepared membranes was investigated, and results indicated that SiNPs-loaded membrane effectively enhanced the flux (5200 Lm−2 h−1).

Polyacrylonitrile/polyimide composite sub-micro fibrous membranes for precise filtration of PM0.26 pollutants

Particulate matter (PM) pollution has enormously threatened ecosystem and public health. Among various air filtration medium, fibrous ones are very attracting and promising, with an array of advantages such as high specific surface area, and good internal connectivity. Even so, the large-scale fabrication of fibrous filtration materials still remains challenging. Here, three-dimensional polyacrylonitrile/polyimide (PAN/PI) composite sub-micro fibrous membranes were fabricated facilely via free surface electrospinning for precise filtration of PM0.26 pollutants, where the waste PI short fibers were utilized as raw material. The resultant composite fibrous membranes, featuring thin fiber diameter (~150 nm), low areal density (<0.8 g m−2), large porosity, and highly tortuous airflow channels with uniform poresize distribution, possessed excellent mechanical property with tensile strength of 4.95 MPa (twice that of pristine PAN), high thermal durability as well as remarkable filtration performance for ultrafine NaCl aerosol particles (≤0.26 µm) even after multiple filtration tests at high airflow velocity of 14.1 cm s−1. The deepened aperture channels inside three-dimensional sub-micro fibrous membranes are tortuous enough for capturing ultrafine PMs from the airstream mainly via diffusion, interception, and impaction mechanisms, and the reported large-scale fabrication of cost-effective homogeneous PAN/PI fibrous filter media is promising for industrial production and commercial applications.

One-step fabrication of multi-scaled, inter-connected hierarchical fibrous membranes for directional moisture transport

HypothesisFunctional textiles engineered for maintaining body comfort by fast sweat release using the directional moisture transport concept are in high demand. However, designing these functional textiles remains a critical job and generally requires multi-step complex fabrication routes. In this regard, developing one-step strategy to fabricate multi-scaled, inter-connected nonwoven-nanofiber/nets hierarchical fibrous composite membranes with asymmetric wettability for enhanced directional moisture transport would be a very fruitful approach. ExperimentComposite membranes were fabricated by the rational combination of commercial polyethylene terephthalate nonwoven (CNW) as hydrophobic layer, and polyamide and silver nanoparticles (PA-Ag) nanofiber/nets as hydrophilic layer via one-step electrospinning process. FindingsThe resultant CNW/PA-Ag nanofiber/net composite membranes were carefully investigated for water vapor transport, moisture management performance, and antibacterial activity. The subsequent membranes not only exhibit exceptionally high one-way moisture transport index (1253%), considerably high water vapor transport rate (11.45 Kg m-2d-1), and overall moisture management capacity (0.91), but also offer high resistance of 16.9 cm H2O to prohibit the moisture drive in the opposite way, and considerable antibacterial activity against Escherichia coli and Staphylococcus aureus. The effective one-step fabrication of such fascinating directional moisture transport membranes with decent antibacterial activity opens a new intuition into the designing of novel functional materials for rapid sweat release and personal drying applications.

A heatproof electrospun PES/PVDF composite membrane as an advanced separator for lithium‐ion batteries

AbstractIn the present paper, the physicochemical properties of a novel composite fibrous membrane, based on a mixture of poly(aryl ether sulfone) (PES) and poly(vinylidene fluoride) (PVDF), as separators for lithium‐ion batteries are reported and discussed. Compared with the pure PVDF fibrous membrane, the introduction of PES can decrease the PVDF crystallinity while increasing the proportion of α‐phase. Meanwhile, the initial thermal decomposition temperature is enhanced by 24°C. Heat shrinkage tests and thermomechanical analyzers indicate the composite membrane has significantly improved thermal‐dimensional stability. The shrinkage rate of the composite membrane after heat‐treated at 180°C for 2 hr is only 4.8%, which is far below the Celgard separator (82%) and the pure PVDF fibrous membrane (75%). The composite membrane with excellent wettability demonstrates a high ionic conductivity (1.69 × 10−3 S cm−1) at room temperature as well as high electrolyte uptake (595%). The cells assembled with the composite membrane exhibit more stable cycle performance, capacity retention, and C‐rate capability than that with polyolefin separator. These results suggest that PES/PVDF composite fibrous membrane is an effective separator for high‐performance Lithium‐ion batteries.

Regulating phase-change temperatures of form-stable phase-change ternary composite fibrous membranes consisting of polystyrene nanofibers and fatty acid eutectics via co-electrospinning method

The fatty acid ternary eutectics such as capric-lauric-myristic acid, capric-lauric-palmitic acid, capric-lauric-stearic acid, capric-myristic-palmitic acid, capric-myristic-stearic acid, and capric-palmitic-stearic acid and quaternary eutectics such as capric-lauric-myristic-palmitic acid, capric-lauric-myristic-stearic acid, capric-lauric-palmitic-stearic acid, capric-myristic-palmitic-stearic acid, and lauric-myristic-palmitic-stearic acid were selected as solid-liquid phase-change materials (PCMs). And then the innovative ternary eutectic/polystyrene (PS)/ternary eutectic and ternary eutectic/PS/quaternary eutectic form-stable phase-change composite fibrous membranes (PCCFMs) were directly prepared by the co-electrospinning method under the same spinning parameters. The as-prepared form-stable PCCFMs exhibited three-dimensional fibrous network structure with the average fiber diameter of about 410–780 nm according to the scanning electron microscopy images. The adhesion among nanofiber intersections was observed occasionally. The differential scanning calorimetry results showed that fatty acid eutectics have been successfully combined into the form-stable PCCFMs, and their melting peak temperatures mostly ranged from 15°C to 21°C with a temperature interval of 1°C. Moreover, the phase-change enthalpies reached about 40–61 kJ kg−1. It is concluded that these electrospun form-stable PCCFMs with appropriate phase-change temperatures could be considered as potential PCMs to be applied in thermo-regulating fibers and textiles.

Super-low thermal conductivity fibrous nanocomposite membrane of hollow silica/polyacrylonitrile

Global warming aggravates mainly due to human activities, such as the massive use of fossil energy and excessive deforestation. Thus, reducing energy waste becomes has gained more importance. Thermal insulation materials with superlow thermal conductivity show notable potential in energy saving. Herein, an adiabatic hollow silica/polyacrylonitrile (SiO2-PAN) fibrous nanocomposite membrane was prepared via electrospinning. Hollow SiO2 spheres were prepared by using tetraethyl orthosilicate as a silica source and hydrothermal carbon spheres as the template. The thermal insulation property of PAN fibrous nanocomposite membrane can be enhanced by appending hollow SiO2 spheres. The solid conduction of the fibrous nanocomposite membrane was reduced by the addition of hollow SiO2 spheres. The composite fibrous nanocomposite membrane is flexible and achieves an optimal thermal conductivity of 16 mW/(m·K). The fibrous nanocomposite membrane can maintain its thermal insulation property and becomes hydrophobic after treatment with silicone oil. The developed membrane provides a new idea for the future development of thermal insulation materials.

Using co-electrospinning method to regulate phase change temperatures of fatty acid eutectic/polystyrene/fatty acid eutectic form-stable phase change composite nanofibrous membranes for thermal energy storage

The seven kinds of fatty acid eutectics including capric-lauric acid (CL), capric-myristic acid (CM), capric-palmitic acid (CP), capric-stearic acid (CS), capric-lauric-myristic acid (CLM), capric-lauric-stearic acid (CLS) and capric-myristic-palmitic acid (CMP) were selected as solid-liquid PCMs. And then co-electrospinning method was used to produce and design innovative fatty acid binary eutectic/polystyrene/fatty acid binary eutectic (i.e., CL/PS/CL, CM/PS/CM, CP/PS/CP, CS/PS/CS, CL/PS/CM, CL/PS/CP, CL/PS/CS, CM/PS/CP, CM/PS/CS and CP/PS/CS) and fatty acid binary eutectic/polystyrene/fatty acid ternary eutectic (i.e., CL/PS/CLM, CM/PS/CLM, CP/PS/CLM, CS/PS/CLM, CL/PS/CLS, CM/PS/CLS, CP/PS/CLS, CS/PS/CLS, CL/PS/CMP, CM/PS/CMP, CP/PS/CMP and CS/PS/CMP) form-stable phase change composite fibrous membranes (PCCFMs) with the melting peak temperatures ranging from about 17 to 24 °C with the temperature interval of 1 °C. The scanning electron microscope images revealed that these electrospun PS-based form-stable PCCFMs exhibited well and stable nanofibrous network structure. The differential scanning calorimetry results indicated that the phase change temperatures of electrospun PS-based form-stable PCCFMs could be regulated to the lower temperature range by changing the type of the loaded fatty acid binary and ternary eutectics, and their phase change enthalpies were approximately 41–60 kJ/kg. Based on the consideration of phase change temperatures, the developed electrospun PS-based form-stable PCCFMs could be more suitable to use in temperature-regulated fibers and textiles as well as energy efficiency building applications.

Electrospun Polymer Composite Membrane with Superior Thermal Stability and Excellent Chemical Resistance for High-Efficiency PM2.5 Capture.

To address the challenge of high-temperature air filtration, a novel electreted polysulfonamide/polyacrylonitrile-boehmite (PSA/PAN-B) composite nanofiber based filter was developed via electrospinning for effective high-temperature dust removal. In this study, the spinnability of PSA was greatly improved by adding a small amount of PAN as an auxiliary polymer, and the introduction of a boehmite electret further significantly reinforced the properties of PSA fibers. As a result, the PSA/PAN-B membrane exhibited a high filtration efficiency (up to 99.52 ± 0.32%), low pressure drop (45.16 ± 1.39 Pa), excellent flexibility, good mechanical properties, high thermal stability (up to approximately 300 °C), and superior chemical resistance. Through data analysis and 3D simulation, the important benefits of the boehmite electret in the optimization of the PSA fibrous membrane performance were determined: it increases the charge storage capacity, constructs a rough surface morphology, improves the specific surface area, and enhances the mechanical properties. More importantly, the PSA/PAN-B film possessed a robust PM2.5 purification capacity, and the particulate matter removal efficiency was kept unchanged after high-temperature, acid, or alkali treatment-a performance derived from the intrinsic molecular structure of PSA. The PSA/PAN-B composite fibrous membrane, with excellent comprehensive properties, is a promising candidate for air filters, especially in harsh environments, further broadening the applications of PSA and providing new insight into the design of high-performance filters with high-temperature and corrosion resistance.

Polyphenylene Sulfide Ultrafine Fibrous Membrane Modified by Nanoscale ZIF-8 for Highly Effective Adsorption, Interception, and Recycling of Iodine Vapor.

In this study, two novel composite membranes containing nanoscale ZIF-8 and polyphenylene sulfide (PPS) nonwoven fabric were prepared via hydrothermal (PPS-ZIF-8) and biomimetic mineralization (PPS-ZIF-8-BSA; BSA, bovine serum albumin) approaches. The biomimetic mineralization approach in particular was extremely rapid and mild, and crystalline ZIF-8 was coated on the PPS substrate in only a few seconds at room temperature. The maximum iodine adsorption capacities of the PPS-ZIF-8 and PPS-ZIF-8-BSA membranes were 2.51 and 2.07 g/g, respectively. The composite fibrous membranes were able to capture trace iodine vapor under differential pressures ranging from 0 to 1000 Pa without almost any iodine vapor leakage. The composite membranes can be applied in harsh environments because of the excellent stability of ZIF-8 and the PPS high-performance fibers. This study provides a promising strategy to fabricate novel adsorption materials for the collection of radioactive iodine during nuclear waste disposal.

Development of electrospun polystyrene-based form-stable phase change ternary composite fibrous membranes with the melting peak temperatures of 15–25 °C for storage and retrieval of thermal energy

The eight kinds of fatty acid binary and ternary eutectics such as capric–lauric acid (CL), capric–myristic acid (CM), capric–palmitic acid (CP), capric–stearic acid (CS), capric–lauric–palmitic acid (CLP), capric–myristic–palmitic acid (CMP), capric–myristic–stearic acid (CMS), and capric–palmitic–stearic acid (CPS) were selected as solid–liquid PCMs in this paper. The innovative electrospun fatty acid binary eutectic/polystyrene/fatty acid ternary eutectic (i.e., CL/PS/CLP, CM/PS/CLP, CP/PS/CLP, CS/PS/CLP, CL/PS/CMS, CM/PS/CMS, CP/PS/CMS, CS/PS/CMS, CL/PS/CPS, CM/PS/CPS, CP/PS/CPS and CS/PS/CPS) and fatty acid ternary eutectic/polystyrene/fatty acid ternary eutectic (i.e., CLP/PS/CMP, CLP/PS/CMS, CLP/PS/CPS, CMP/PS/CMS, CMP/PS/CPS and CMS/PS/CPS) form-stable phase change composite fibrous membranes (PCCFMs) were fabricated by co-electrospinning. The morphological structure, phase change temperatures, and enthalpies were investigated by scanning electron microscope (SEM) and differential scanning calorimetry (DSC), respectively. The SEM images showed that the PS-based phase change composite fibers were collected to form form-stable PCCFMs with the average fiber diameter of about 335–640 nm. The DSC analysis indicated that the melting peak temperatures of electrospun PS-based form-stable PCCFMs can be adjusted to 15–25 °C with the temperature interval of 1 °C by combining the both of fatty acid binary and ternary eutectics into the PS supporting fibers. These PS-based form-stable PCCFMs can be recommended for potential low-temperature thermal energy storage applications to regulate temperature and satisfy the human thermal comfortability.

Preparation and characterization of composite fibrous membranes for oil spill cleanup

In this study, polyacrylonitrile (PAN) electrospun fibrous membranes were manufactured and applied for oil spill cleanup. Two kinds of composite fibrous membranes composed of PAN electrospun fibrous membranes and polyethylene/polyethylene terephthalate (PE/PET) core-shell fiber nonwoven fabric were fabricated. The fibrous structure, mechanical properties and surface wettability for water and oil, as well as oil absorption capacities and dynamic oil retention of the membranes, were investigated in detail. The addition of nonwoven fabric significantly enhanced the tensile strength of the PAN fibrous membranes. The oil absorption mechanisms of different membranes were studied as well. The sandwich structure composite fibrous membranes exhibited excellent mechanical property and oil absorption capacity, making it a promising candidate for treatment of oily wastewater.

Superhydrophobic hierarchical fiber/bead composite membranes for efficient treatment of burns

One of the current challenges in burn wound care is the development of multifunctional dressings that can protect the wound from bacteria or organisms and promote skin regeneration and tissue reconstitution. To this end, we report the design and fabrication of a composite electrospun membrane, comprised of electrospun polylactide: poly(vinyl pyrrolidone)/polylactide: poly(ethylene glycol) (PLA:PVP/PLA:PEG) core/shell fibers loaded with bioactive agents, as a functionally integrated wound dressing for efficient burns treatment. Different mass ratios of PLA:PVP in the shell were screened to optimize mechanical, physicochemical, and biological properties, in addition to controlled release profiles of loaded antimicrobial peptides (AMPs) from the fibers for desirable antibacterial activity. Fibroblasts were shown to readily adhere and proliferate when cultured on the membrane, indicating good in vitro cytocompatibility. The introduction of PLA beads by electrospraying on one side of the membrane resulted in biomimetic micro-nanostructures similar to those of lotus leaves. This designer structure rendered the composite membranes with superhydrophobic property to inhibit the adhesion/spreading of exogenous bacteria and other microbes. The administration of the resulting composite fibrous membrane on burnt skin in an infected rat model led to faster healing than a conventional product (sterile silicone membrane) and control detailed herein. These composite fibrous membranes loaded with bioactive drugs provide an integrated strategy for promoting burn wound healing and skin regeneration. Statement of SignificanceTo address an urgent need in complex clinical requirements on developing a new generation of wound dressings with integrated functionalities. This article reports research work on a hierarchical fiber/bead composite membranes design, which combines a lotus-leaf-like superhydrophobic surface with drugs preloaded in the core and shell of fibers for effective burn treatment. This demonstrates a balance between simplified preparation processes and increased multifunctionality of the wound dressings. The creation of hierarchically structured surfaces can be readily achieved by electrospinning, and the composite dressings possessed a considerable mechanical strength, effective wound exudate absorption and permeability, good biocompatibility, broad antibacterial ability and promoting wound healing etc. Thus, our work unveils a promising strategy for the development of functionally integrated wound dressings for burn wound care.

Fish Collagen and Hydroxyapatite Reinforced Poly(lactide-co-glycolide) Fibrous Membrane for Guided Bone Regeneration

The purpose of this study was to fabricate a low-immunogenicity fish collagen (FC) and bioactive nanohydroxyapatite (n-HA) enhanced poly(lactide- co-glycolide) (PLGA) nanofibrous membrane for guided bone regeneration (GBR) via electrospinning. The physicochemical properties and morphology study revealed that FC and n-HA particles were homogeneously dispersed in the PLGA fibrous matrix. Notably, the formation of enhanced polymeric chain network due to the interaction between FC and PLGA significantly improved the tensile strength of the PLGA membrane. The incorporation of FC altered the degradation behavior of fibers and accelerated the degradation rate of the PLGA-based membranes. Moreover, the membranes exhibited favorable cytocompatibility with bone mesenchymal stem cells (BMSCs) and human gingiva fibroblasts (HGF) cells. More importantly, the optimized membrane satisfied the requirements of the 'Biological evaluation of medical devices' during the incipient biosafety evaluation. All the results indicate that this composite fibrous membrane exhibits significant potential for guided bone or tissue regeneration.

High Performance Piezoelectric Nanogenerators Based on Electrospun ZnO Nanorods/Poly(vinylidene fluoride) Composite Membranes

A novel flexible zinc oxide/poly(vinylidene fluoride) (ZnO/PVDF) nanocomposite was prepared by electrospinning for fabricating a piezoelectric nanogenerator (PNG). The ZnO nanoparticles (NPs) and nanorods (NRs) were used as nanofillers of piezoelectric PVDF to prepare fibrous nanocomposite membranes. It has been found that the addition of piezoelectric ZnO NPs and NRs can improve the overall performance of the PNGs fabricated with the electrospun membranes. A large electrical throughput (open circuit voltage ∼85 V and short circuit current ∼2.2 μA) from the ZnO NR/PVDF fiber membrane-based PNG (ZR-PNG) indicates that ZnO NRs are effective functional fillers for PVDF. The high aspect ratio and flexibility characteristics of ZnO NRs were found to be highly beneficial for improving the piezoelectric properties of the nanocomposites. ZnO NRs act as nucleating agents of β-phase PVDF, and ZnO NRs can also produce piezoelectric charges when they deform with the composite fibrous membrane. It has been concluded t...

Nanocrystalline Cellulose/Polyvinylpyrrolidone Fibrous Composites Prepared by Electrospinning and Thermal Crosslinking

Nanocellulose/polyvinylpyrrolidone (nCel/PVP) fibrous composite materials containing rod-like nanocrystalline cellulose particles with the lengths varying in the range from 100 to 2000 nm were prepared by using DC electrospinning. The particle size had a strong effect on the precursor viscosity, process efficiency, and resulting fiber diameter. The thermal crosslinking of nCel/PVP composite nanofibers with up to 1.0 : 8.0 nCel/PVP weight ratio resulted in fibrous membranes with textural, air transport, and mass swelling properties varying significantly with the size of cellulose particles. The presence of nCel particles increased the oxidation resistance of PVP during the crosslinking and affected the morphological changes of nCel/PVP fibrous membranes in aqueous solutions. Particles with the smallest size improved the strength of the membrane but decreased its mass swelling capacity, whereas the larger particles led to a more porous and flexible, but mechanically weaker, membrane structure with a higher swelling ability. Thus, by using the nCel particles of different size and shape, the properties of nCel/PVP composite fibrous membranes can be tailored to a specific application.

The effect of nano-zirconia on the morphology and mechanical properties of PVDF/PAN membrane as separators in super capacitors

The PVDF/PAN/ZrO2 (zirconia) composite fibrous membranes were fabricated by electrospinning. The effects of ZrO2 content on solution properties, mechanical properties and crystallisation behaviours as well as related morphology were systematically evaluated. The scanning electron microscopy (SEM) was used to investigate the effect of ZrO2 content on the morphology of PVDF/PAN/ZrO2 composite fibrous membranes, which showed that the diameter is only 0.8 μm when the ZrO2 is 0.4%. It could be attributed to the enhancement of solution conductivity by ZrO2 addition. Nitrogen adsorption based on Brunauer-Emmett-Teller (BET) principle was employed to measure the specific surface area, which indicated that the specific surface area increased about 1.8 times for composite membranes compared to the PVDF/PAN membrane when the ZrO2 content was 0.4%. The tensile strength of fibrous membranes increased from 2.74 of pure PVDF/PAN to 5.11 MPa of PVDF/PAN/ZrO2 when the ZrO2 content was 0.4%. The differential scanning calorimetry (DSC) results showed that the crystallinity and orientation enhanced with increasing of ZrO2, which was beneficial to improve the tensile strength. The Tg and Tc shifted to high temperature with ZrO2 increases, which demonstrated that ZrO2 promoted the heterogeneous nucleation and formed perfect crystal structure.