The production of ultrafine fibres using variations of the centrifugal spinning technique

Centrifugal spinning uses high speed spinneret rotation to generate and elongate jets of polymeric material in to fine fibres. Variations of this basic technology has been used to form ultrafine fibres from: polypropylene (PP), ubiquitous in the nonwovens industry and a key material for nonwovens; polycaprolactone (PCL), a biocompatible polymer used previously as a biological scaffold; and polyvinylpyrrolidone with 1-triacontane (PVP/TA), a copolymer found in the cosmetics industry. This work demonstrated the melt centrifugal spinning of PP into sub-micron fibres ≤ 500 nm in diameter, and PCL fibres ≤900 nm in diameter. The influences of material properties and processing conditions on the fibre and webs properties were investigated and relationships established. For melt spinning, increasing the rotational speed will reduce the average fibre diameter and when solution spinning PCL a binary solvent produced finer fibres with increased surface textures. The spinning of PVP/TA into fibres demonstrated in this work has been previously unreported. PVP/TA fibres were created by centrifugal spinning at low temperatures were as fine as 1.5 µm on average. These fibres were used as an adsorbent and showed an affinity for the capture and retention of disperse dyes and hydrocarbons on the fibre surface. Carbon nanotube composite fibres were created by dispersing the nanotubes in both PP and PCL polymers using ultrasonic waves. The addition of carbon nanotubes significantly increased the level of beading during spinning in both PP and PCL as their presence causing an increase in Rayleigh instabilities. The addition of nanotubes did not improve web strength of the products compared to virgin polymer. Overall, centrifugal spinning has proven to be a highly versatile technique, capable of producing ultrafine fibres from a range of polymer feed materials which have potential to be utilised in a range of specialist applications.