Electrospinning of nanofibre yarns using rotating ring collector

 In this project, a novel ring collector was used to convert newly electrospun nanofibres into yarn. This setup has been designed to separate electrospinning from yarn drafting/twisting in two distinct zones. Three different types of electrospinning systems, i.e. needle, needleless, and needle/needleless hybrid, were utilized to produce nanofibre yarns.

Direct electrospinning of nanofibre yarns using a rotating ring collector

Nanofibres prepared by electrospinning typically have randomly oriented fibrous structure. They have large surface-to-volume (or weight) ratio and excellent porous characteristic, which have shown enormous potential in diverse applications. However, electrospun nanofibres are often prepared in the form of randomly orientated fibrous web, which are fragile and difficult to be tailored in fibrous structures. Herein, we demonstrate a novel yarn electrospinning method which uses a rotating ring collector to convert newly electrospun nanofibres directly into a continuous yarn. The use of ring collector separates the yarn formation from the electrospinning zone. The deposition of later-spun nanofibres to the inner surface of fibrous cone eliminates hooked or curled nanofibres in the final yarn. The effects of polymer concentration and operating parameters on nanofibre and yarn morphology, diameter and the ring collector on yarn twist feature were examined. The nanofibre yarns had a surface twist angle up to 54.4°, and tensile strength as high as 93.6 MPa (elongation at break 242.6%). Increasing twist levels improves tensile strength and strain values.

Highly-twisted, continuous nanofibre yarns prepared by a hybrid needle-needleless electrospinning technique

Nanofibres prepared by electrospinning have shown enormous potential for various applications. They are obtained predominantly in the form of nonwoven fibre webs. The 2-dimensional nonwoven feature and fragility have considerably confined their further processing into fabrics through knitting or weaving. Nanofibre yarns, which are nanofibre bundles with continuous length and a twist feature, show improved tensile strength, offering opportunities for making 3-dimensional fibrous materials with precisely controlled fibrous architecture, porous features and fabric dimensions. Despite a few techniques having been developed for electrospinning nanofibre yarns, they are chiefly based on the needle electrospinning technique, which often has low nanofibre productivity. In this study, we for the first time report a nanofibre yarn electrospinning technique which combines both needle and needleless electrospinning. A rotating intermediate ring collector was employed to directly collect freshly-electrospun nanofibres into a fibrous cone, which was further drawn and twisted into a nanofibre yarn. This novel system was able to produce high tenacity yarn (tensile strength 128.9 MPa and max strain 222.1%) at a production rate of 240 m h^-1, with a twist level up to 4700 twists per metre. The effects of various parameters, e.g. position of the electrospinning units, operating conditions and polymer concentration, on nanofibre and yarn production were examined.

Supramolecular ionic networks with superior thermal and transport properties based on novel delocalized di-anionic compounds

Supramolecular ionic networks based on highly delocalized dianions having (trifluoromethane-sulfonyl)imide, (propylsulfonyl)methanide and (cyano-propylsulfonyl)imide groups were developed and their physical properties were examined in detail. Most of the synthesized compounds were semi-crystalline possessing Tm values close to 100°C; however, amorphous networks were also obtained using aromatic asymmetric dianions. Rheological measurements in temperature sweep tests at a constant frequency confirmed two different behaviors: a fast melting close to the Tm for semi-crystalline materials and a thermoreversible network for liquid transition for the amorphous supramolecular ionic networks. It was found that the amorphous ionic networks showed significantly higher ionic conductivity (10^-3 S cm^-1 at 100°C) than the crystalline ionic networks (10^-6 S cm^-1) and previously reported amorphous citrate ionic networks (10^-5 S cm^-1). The supramolecular ionic networks containing hydrophobic (trifluoromethanesulfonyl)imide groups demonstrated improved water stability and higher thermal stability than the previously synthesized carboxylate ones. Noticeably, the obtained amorphous supramolecular ionic networks combine not only high ionic conductivity and thermal stability, but also self-healing properties into the same material.