This paper reports the first study on centrifugal spinning of PHBV fibres. Fibres were spun from solution using a range of polymer concentrations, spin speeds and spinneret to collector distances. A PHBV polymer concentration of 25% w/v spun at 9000rmin produced the highest quality fibres, with fibre diameters predominantly in the 0.5-3μm range. The rate at which fibre could be produced at the 9000rmin spin speed and with a spinneret to collector distance of 39.2cm was equivalent to 11km of fibre per minute per needle. Average fibre strengths of 3MPa were achieved, together with average moduli of 100MPa, indicating that the fibres had higher strength but lower stiffness than electrospun PHBV. The productivity and mechanical properties achieved, together with the excellent biocompatibility of PHBV, means that these fibres have potential for application in a range of biomedical applications.
Melt centrifugal spinning has been used to successfully produce nanofibres from compounds of polypropylene (PP) and multi-walled carbon nanotubes (MWNTs) at a concentration of 1%. The compounds were prepared either via twin screw compounding or by dissolution in decalin with sonication. Nanofibre production was conducted by centrifugal spinning in a Forcespinner™, a technology capable of producing nanofibres with a high material throughput. Processing via dissolution resulted in a reduction in the size of the MWNT agglomerations in the polymer, which led to a more uniform fibre morphology and a reduced incidence of bead defects as compared to products produced from the melt extrusion compound. The addition of a nonionic surfactant (Triton X-100) to the compound solution aided dispersion of the MWNTs as determined by optical light microscopy of thin cast films and produced fibres with the lowest mean diameter. The mean fibre diameter in the as-spun webs prepared by dissolution of PP in decalin with sonication was found to decrease with increasing spinneret speed; however, a similar trend was not observed for fibres generated from the melt compounded material.
Polyvinylpyrrolidone/1-triacontene (PVP/TA) copolymer fibre webs produced by centrifugal melt spinning were studied to determine the influence of jet rotation speed on morphology and internal structure as well as their potential utility as adsorbent capture media for disperse dye effluents. Fibres were produced at 72°C with jet head rotation speeds from 7000 to 15,000 r min -1 . The fibres were characterised by means of SEM, XRD and DSC. Adsorption behaviour was investigated by means of an isothermal bottle point adsorption study using a commercial disperse dye, Dianix AC-E. Through centrifugal spinning nanofibers and microfibers could be produced with individual fibres as fine as 200-300 nm and mean fibre diameters of ca. 1-2 lm. The PVP/TA fibres were mechanically brittle with characteristic brittle tensile fracture regions observed at the fibre ends. DSC and XRD analyses suggested that this brittleness was linked to the graft chain crystallisation where the PVP/TA was in the form of a radial brush copolymer. In this structure, the triacontene branches interlock and form small lateral crystals around an amorphous backbone. As an adsorbent, the PVP/TA fibres were found to adsorb 35.4 mg g -1 compared to a benchmark figure of 30.0 mg g -1 for a granular-activated carbon adsorbent under the same application conditions. PVP/TA is highly hydrophobic and adsorbs disperse dyes through the strong ''hydrophobic bonding'' interaction. Such fibrous assemblies may have applications in the targeted adsorption and separation of non-polar species from aqueous or polar environments.
Reinforcement of flexible fibre reinforced plastic (FRP) composites with standard textile fibres is a potential low cost solution to less critical loading applications. The mechanical behaviour of FRPs based on mechanically bonded nonwoven preforms composed of either low or high modulus fibres in a thermoplastic polyurethane (TPU) matrix were compared following compression moulding. Nonwoven preform fibre compositions were selected from lyocell, polyethylene terephthalate (PET), polyamide (PA) as well as para-aramid fibres (polyphenylene terephthalamide; PPTA). Reinforcement with standard fibres manifold improved the tensile modulus and strength of the reinforced composites and the relationship between fibre, fabric and composite’s mechanical properties was studied. The linear density of fibres and the punch density, a key process variable used to consolidate the nonwoven preform, were varied to study the influence on resulting FRP mechanical properties. In summary, increasing the strength and degree of consolidation of nonwoven preforms did not translate to an increase in the strength of resulting fibre reinforced TPU-composites. The TPU composite strength was mainly dependent upon constituent fibre stress-strain behaviour and fibre segment orientation distribution.
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