Toughened electrospun nanofibers from crosslinked elastomer-thermoplastic blends

A crosslink-able elastomeric polyester urethane (PEU) was blended with a thermoplastic, polyacrylonitrile (PAN), and electrospun into nanofibres. The effects of the PEU/PAN ratio and the crosslinking reaction on the morphology and the tensile properties of the as-spun fibre mats were investigated. With the same overall polymer concentration (9 wt %), the nanofibre containing higher composition of PEU shows a slight decrease in the average fibre diameter, but the tensile strength, the elongation at break and tensile modulus of the nanofibre mats are all improved. These tensile properties are further enhanced by slight crosslinking of the PEU component within the nanofibres.

Modified two-strand spinning (part III : yarn performance)

In this final part of the series, modified two-strand spun yarns are produced on a modified Sirospun system. The yarns are then evaluated against conventional Sirospun yarns.

Applications of electrospun nanofibers

Polymeric nanofiber non-woven materials produced by electrospinning have extremely high surface-to-mass (or volume) ratio and a porous structure with excellent pore-interconnectivity. These characteristics plus the functionalities and surface chemistry of the polymer itself impart the nanofibers with desirable properties for a range of advanced applications. This review summarizes the recent progress in electrospun nanofibers, with an emphasis on their applications.

Electrospun single-walled carbon nanotube/polyvinyl alcohol composite nanofibers : structure-property relationships

Polyvinyl alcohol (PVA) nanofibers and single-walled carbon nanotube (SWNT)/PVA composite nanofibers have been produced by electrospinning. An apparent increase in the PVA crystallinity with a concomitant change in its main crystalline phase and a reduction in the crystalline domain size were observed in the SWNT/PVA composite nanofibers, indicating the occurrence of a SWNT-induced nucleation crystallization of the PVA phase. Both the pure PVA and SWNT/PVA composite nanofibers were subjected to the following post-electrospinning treatments: (i) soaking in methanol to increase the PVA crystallinity, and (ii) cross-linking with glutaric dialdehyde to control the PVA morphology. Effects of the PVA morphology on the tensile properties of the resultant electrospun nanofibers were examined. Dynamic mechanical thermal analyses of both pure PVA and SWNT/PVA composite electrospun nanofibers indicated that SWNT–polymer interaction facilitated the formation of crystalline domains, which can be further enhanced by soaking the nanofiber in methanol and/or cross-linking the polymer with glutaric dialdehyde.

Current developments and future challenges for the creation of aortic heart valve

The concept of tissue-engineered heart valves offers an alternative to current heart valve replacements that is capable of addressing shortcomings such as life-long administration of anticoagulants, inadequate durability, and inability to grow. Since tissue engineering is a multifaceted area, studies conducted have focused on different aspects such as hemodynamics, cellular interactions and mechanisms, scaffold designs, and mechanical characteristics in the form of both in vitro and in vivo investigations. This review concentrates on the advancements of scaffold materials and manufacturing processes, and on cell–scaffold interactions. Aside from the commonly used materials, polyglycolic acid and polylactic acid, novel polymers such as hydrogels and trimethylene carbonate-based polymers are being developed to simulate the natural mechanical characteristics of heart valves. Electrospinning has been examined as a new manufacturing technique that has the potential to facilitate tissue formation via increased surface area. The type of cells utilized for seeding onto the scaffolds is another factor to take into consideration; currently, stem cells are of great interest because of their potential to differentiate into various types of cells. Although extensive studies have been conducted, the creation of a fully functional heart valve that is clinically applicable still requires further investigation due to the complexity and intricacies of the heart valve.

Preparation of nanofibre yarns from electrospun nonwoven strips

From ancient to modern time, humans have been trying to use finer fibres to make fibrous products for various purposes and believing that finer fibres have better aesthetic qualities. So far, the commercial fibres have been reduced to microns in diameter, but it seems difficult to further reduce the fibre fineness to submicrons using conventional fibre-making techniques.
Electrospinning is a promising technique to produce continuous fibres with diameters on nanometre scales. This technique involves stretching a polymer fluid under a strong electric field into fine filaments, which are deposited randomly on the electrode collector forming a nonwoven nanofibre mat in most cases. Despite considerable efforts in exploring the applications of electrospun nanofibres in non-fibrous fields [1], very limited work has been conducted on using this material to process mechanically robust nanofibre yarns [2,3].

Nano related research in fibres and textiles

With the increasing hype surrounding what nanotechnology can actually deliver, research emphasis in this area needs to be placed on how nanotechnology can bring tangible benefits to existing industries and ordinary consumers. This paper gives selected examples of real world applications of nano-structured materials, including nano fibrous and particulate materials. It reviews recent research into nano-structured surface coating of textile substrates for enhanced functionalities, and the development of fine and uniform nanofibres for advanced applications. Emphasis has been placed on relevant research activities in the Centre for Material and Fibre Innovation at Deakin University, Australia. In the nano-structured surface coating area, several examples of enhancing fabric performance and functionality are provided, including silica coating for photochromic textiles, superhydrophobic surface coating and transparent ZnO coating to reduce colour fading of textiles exposed to UV radiation. In the nanofibre area, these activities include: elimination of beaded fibres without increasing the average diameter of the electrospun nanofibres, electrospinning of side-by-side bi-component nanofibres, new insight into the evolution of fibre morphology in electrospinning and the electrospinning technology itself.

Carbon nanotube polymer composites and nanofibres

This study examined how carbon nanotubes (CNTs) in electrospun polymeric nanofibres influenced the polymer morphology, and how polymer morphology change induced by different post-electrospinning treatments influenced CNT-polymer interaction and nanofibre properties. The results showed that both the polymer structure and morphology played important roles in determining the composite and nanofibre properties.

Electrospun nanofibres

This research contributes new knowledge to fundamental understanding and applications of nanofibre materials made by the electrospinning technique. An innovative method was developed to visualise the fibre thinning, and the nanofibres with improved mechanical properties and controlled surface wettability were prepared. These nanofibres have shown significant potential in wound dressing application.

Carbon nanotubes reinforced electrospun polymer nanofibres

With the rapid development in nanoscience and nanotechnology, there is an ever increasing demand for polymer fibres of diameters down to a nanometre scale having multiple functionalities. Electrospinning, as a simple and efficient nanofibre-making technology, has been used to produce polymer nanofibres for diverse applications. Electrospun nanofibres
based on polymer/carbon nanotube (CNT) composites are very attractive multifunctional nanomaterials because they combine the remarkable mechanical and electronic properties of CNTs and the confinement-enhanced CNTs alignment within the nanofibre structure, which could greatly improve the fibre mechanical, electrical and thermal properties. In this chapter, we summarise recent research progress on electrospun CNTs/polymer nanofibres, with an emphasis on fibre mechanical properties and structure-property attributes. Outlook towards the challenge and future directions in this field is also presented.

Properties of a carbon-fibre composite modified by electrospun poly (vinylidene fluoride)

The interlaminar toughening of a carbon-fibre reinforced composite by incorporation of electrospun polyvinylidene fluoride (PVDF) nanofibrous membranes was explored in this work. The nanofibres were electrospun directly onto commercial pre-impregnated carbon fibre materials under optimised conditions and PVDF was found to primarily crystallise in its β phase polymorphic form. There is strong evidence from DMTA analysis to suggest that a partial miscibility between the amorphous phases of the PVDF nanofibres and the epoxy exists. The improved plastic deformation at the crack tip after inclusion of the nanofibres was directly translated to a 57% increase in the mode II interlaminar fracture toughness (in-plane shear failure). Conversely, the fracture toughness in mode I (opening failure) was slightly lower than the reference by approximately 20%, and the results were interpreted from the complex micromechanisms of failure arising from the changes in polymorphism of the PVDF.

Synthesis and characterization of silver nanoparticles and titanium oxide nanofibers : toward multifibrous nanocomposites

A new method was investigated to produce new multiscale fibrous nanocomposites comprised of titanium oxide (TiO₂) nanofibers and silver (Ag) nanoparticles (NPs). The process involved electrospinning TiO₂ precursor solution containing colloidal solution of Ag NPs, and organic solvent (dimethyl-n′n-formamide) to fabricate a porous, nonwoven, free-standing nanofiber mesh. Postprocess heating of the electrospun nanofibers entailed calcination in air environment at 500°C for 3 h. Microemulsion processing was used to generate NPs of Ag in a monodispersed distribution throughout the colloidal solution. X-ray diffraction data were consistent with the anatase phase of TiO2, while transmission electron microscopy and hydrogen desorption measurements revealed a very porous microstructure. It was demonstrated that NP colloidal stability is solvent dependent. It is anticipated that incorporation of metal particles in nanofibers will lead to enhanced photocurrent generation, when used in functional devices.

Fast responsive and morphologically robust thermo-responsive hydrogel nanofibres from poly(N-isopropylacrylamide) and POSS crosslinker

Stable thermo-responsive hydrogel nanofibres have been prepared by electrospinning of commercial poly(N-isopropylacrylamide) (PNIPAM) in the presence of a polyhedral oligomeric silsesquioxane (POSS) possessing eight epoxide groups and of an organic-base catalyst, followed by a heat curing treatment. The nanofibres showed excellent hydrogel characteristics with fast swelling and de-swelling responses triggered by temperature changes. They were also morphologically robust as their physical integrity was preserved upon repeated hydration/dehydration cycles and exposure to solvents.