Recent advances in core/shell bicomponent fibers and nanofibers: A review

Fabricating Fibers of a Porous-Polystyrene Shell and Particle-Loaded Core

Polystyrene (PS) polymers have broad applications in protective packaging for food shipping, containers, lids, bottles, trays, tumblers, disposable cutlery and the making of models. Currently, most PS products, such as foams, are not accepted for recycling due to a low density in the porous structure. This poses a challenge for logistics as well as creating a lack of incentive to invest in high-value products. This study, however, demonstrated the use of a dry-jet wet-spinning technique to manufacture continuous PS fibers enabled by an in-house designed and developed spinning apparatus. The manufactured fibers showed porosity in the shell and the capability to load particles in their core, a structure with high potential use in environmentally relevant applications such as water treatment or CO2 collections. A two-phase liquid-state microstructure was first achieved via a co-axial spinneret. Following coagulation procedures and heat treatment, phase-separation-based selective dissolution successfully generated the porous-shell/particle-core fibers. The pore size and density were controlled by the porogen (i.e., PEG) concentrations and examined using scanning electron microscopy (SEM). Fiber formation dynamics were studied via rheology tests and gelation measurements. The shell components were characterized by tensile tests, thermogravimetric analysis, and differential scanning calorimetry for mechanical durability and thermal stability analyses.

Novel Bicomponent Functional Fibers with Sheath/Core Configuration Containing Intumescent Flame-Retardants for Textile Applications

The objective of this study is to examine the effect of intumescent flame-retardants (IFR’s) on the spinnability of sheath/core bicomponent melt-spun fibers, produced from Polylactic acid (PLA) single polymer composites, as IFR’s have not been tested in bicomponent fibers so far. Highly crystalline PLA-containing IFR’s was used in the core component, while an amorphous PLA was tested in the sheath component of melt-spun bicomponent fibers. Ammonium polyphosphate and lignin powder were used as acid, and carbon source, respectively, together with PES as a plasticizing agent in the core component of bicomponent fibers. Multifilament fibers, with sheath/core configurations, were produced on a pilot-scale melt spinning machine, and the changes in fibers mechanical properties and crystallinity were recorded in response to varying process parameters. The crystallinity of the bicomponent fibers was studied by differential scanning calorimetry and thermal stabilities were analyzed by thermogravimetric analysis. Thermally bonded, non-woven fabric samples, from as prepared bicomponent fibers, were produced and their fire properties, such as limiting oxygen index and cone calorimetry values were measured. However, the ignitability of fabric samples was tested by a single-flame source test. Cone calorimetry showed a 46% decline in the heat release rate of nonwovens, produced from FR PLA bicomponent fibers, compared to pure PLA nonwovens. This indicated the development of an intumescent char by leaving a residual mass of 34% relative to the initial mass of the sample. It was found that the IFRs can be melt spun into bicomponent fibers by sheath/core configuration, and the enhanced functionality in the fibers can be achieved with suitable mechanical properties.

Coaxial Electrospinning Formation of Complex Polymer Fibers and their Applications

The formation of fibers by electrospinning has experienced explosive growth in the past decade, recently reaching 4,000 publications and 1,500 patents per year. This impressive growth of interest is due to the ability to form fibers with a variety of materials, which lend themselves to a large and rapidly expanding set of applications. In particular, coaxial electrospinning, which forms fibers with multiple core-sheath layers from different materials in a single step, enables the combination of properties in a single fiber that are not found in nature in a single material. This article is a detailed review of coaxial electrospinning: basic mechanisms, early history and current status, and an in-depth discussion of various applications (biomedical, environmental, sensors, energy, catalysis, textiles). We aim to provide readers who are currently involved in certain aspects of coaxial electrospinning research an appreciation of other applications and of current results.

Drug Delivery Applications of Core-Sheath Nanofibers Prepared by Coaxial Electrospinning: A Review

Electrospinning has emerged as one of the potential techniques for producing nanofibers. The use of electrospun nanofibers in drug delivery has increased rapidly over recent years due to their valuable properties, which include a large surface area, high porosity, small pore size, superior mechanical properties, and ease of surface modification. A drug loaded nanofiber membrane can be prepared via electrospinning using a model drug and polymer solution; however, the release of the drug from the nanofiber membrane in a safe and controlled way is challenging as a result of the initial burst release. Employing a core-sheath design provides a promising solution for controlling the initial burst release. Numerous studies have reported on the preparation of core-sheath nanofibers by coaxial electrospinning for drug delivery applications. This paper summarizes the physical phenomena, the effects of various parameters in coaxial electrospinning, and the usefulness of core-sheath nanofibers in drug delivery. Furthermore, this report also highlights the future challenges involved in utilizing core-sheath nanofibers for drug delivery applications.

A Review of Recent Advances in Nanoengineered Polymer Composites

This review paper initially summarizes the latest developments in impact testing on polymer matrix composites collating the various analytical, numerical, and experimental studies performed since the year 2000. Subsequently, the scientific literature investigating nanofiller reinforced polymer composite matrices as well as self-healing polymer matrix composites by incorporating core-shell nanofibers is reviewed in-depth to provide a perspective on some novel advances in nanotechnology that have led to composite developments. Through this review, researchers can gain a representative idea of the state of the art in nanotechnology for polymer matrix composite engineering, providing a platform for further study of this increasingly industrially significant material, and to address the challenges in developing the next generation of advanced, high-performance materials.

Electrospun acellular scaffolds for mimicking the natural anisotropy of the extracellular matrix

In tissue engineering, the use of scaffolds helps establish a synergistic relationship between the scaffolds and the tissues by improving cell–scaffold interaction. This interaction is enhanced when physiologically relevant biophysical cues are replicated in the artificial scaffolds. Here, we present a novel scaffold that mimics the natural anisotropy of the native extracellular matrix of tissues, fabricated by electrospinning a combination of three polymers: polycaprolactone (PCL), polyvinylidene fluoride (PVDF) and polyaniline (PANI). The scaffolds were characterized for their morphology, surface and mechanical properties. Rat cardiomyoblast (H9c2) cells, cultured on the PCL–PANI–PVDF scaffold, demonstrated cell alignment, penetration and proliferation across the entire surface area of the scaffold without any external chemical or physical stimuli. The PCL–PANI–PVDF scaffold, unlike other scaffolds, does not require post-processing or specific temperature conditions of storage, prior to use. These acellular scaffolds fabricated through polymer blending, open new avenues for research on functional acellular scaffolds for tissue engineering, based on synthetic materials.

Co-axial electrospinning of three immiscible polymers by sequentially blending in solvents of different boiling points to obtain biomimetic scaffolds.

Efficient Synthesis of PVDF/PI Side-by-Side Bicomponent Nanofiber Membrane with Enhanced Mechanical Strength and Good Thermal Stability

Bicomponent composite fibers, due to their unique versatility, have attracted great attention in many fields, such as filtration, energy, and bioengineering. Herein, we efficiently fabricated polyvinylidene fluoride/polyimide (PVDF/PI) side-by-side bicomponent nanofibers based on electrospinning, which resulted in the synergism between PVDF and PI, and eventually obtained the effect of 1 + 1 > 2. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the morphology and chemical structure of nanofibers, indicating that a large number of side-by-side nanofibers were successfully prepared. Further, the thermal stability, mechanical strength, and filtration properties of PVDF/PI were carefully investigated. The results revealed that the bicomponent nanofibers possessed both good mechanical strength and remarkable thermal stability. Moreover, the mechanical properties of PVDF/ PI were strengthened by more than twice after the heat treatment (7.28 MPa at 25 °C, 15.49 MPa at 230 °C). Simultaneously, after the heat treatment at 230 °C for 30 min, the filtration efficiency of PVDF/PI membrane was maintained at about 95.45 ± 1.09%, and the pressure drop was relatively low. Therefore, the prepared PVDF/PI side-by-side bicomponent nanofibers have a favorable prospect of application in the field of medium- and high-temperature filtration, which further expands the application range of electrospun fiber membranes.

A ternary nanofibrous scaffold potential for central nerve system tissue engineering

In the present research, a ternary polycaprolactone (PCL)/gelatin/fibrinogen nanofibrous scaffold for tissue engineering application was developed. Through this combination, PCL improved the scaffold mechanical properties; meanwhile, gelatin and fibrinogen provided more hydrophilicity and cell proliferation. Three types of nanofibrous scaffolds containing different fibrinogen contents were prepared and characterized. Morphological study of the nanofibers showed that the prepared nanofibers were smooth, uniform without any formation of beads with a significant reduction in nanofiber diameter after incorporation of fibrinogen. The chemical characterization of the scaffolds confirmed that no chemical reaction occurred between the scaffold components. The tensile test results of the scaffolds showed that increasing in fibrinogen content led to a decrease in mechanical properties. Furthermore, adipose-derived stem cells were employed to evaluate cell-scaffold interaction. Cell culture results indicated that higher cell proliferation occurred for the higher amount of fibrinogen. Statistical analysis was also carried out to evaluate the significant difference for the obtained results of water droplet contact angle and cell culture. Therefore, the results confirmed that PCL/gel/fibrinogen scaffold has a good potential for tissue engineering applications including central nerve system tissue engineering. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2394-2401, 2018.