Electrospinning short polymer micro-fibres with average aspect ratios in the range of 10-200

Ultra fine short fibres have a variety of applications. Short aligned fibres or a mixture of short and long fibres can reinforce brittle materials, alter the appearance, texture and durability of synthetic fibres, and adjust the strength, toughness and stiffness of a composite material. Among electrospun products, short fibres are usually produced by secondary processing of continuous as-spun fibres. However, this is not entirely straightforward or cost-effective due to the efficiency of the secondary process and the relatively low tensile strength of the electrospun ultrafine fibres. Besides, sub-micrometre size fibres with an average aspect ratio (AR) <200 have not been directly produced without further processing by changing collector geometry in electrospinning. Using a model polymer, polymethylsilsesquioxane (PMSQ), short micro-fibres with 10∈<∈AR∈<∈200 were electrospun directly in this work, i.e. without the need for a secondary process. The AR and particularly fibre length were shown to be strongly influenced by the solvent system used for electrospinning and the molecular weight ( M-w) of the polymer. When using PMSQ1 ( M-w=7500) in methanol instead of acetone, short fibres with AR <200 were produced instead of continuous fibres. Moreover, when M-w of the polymer was decreased from 7500 (PMSQ1) to 4300 (PMSQ2), with all other conditions kept constant, significant reduction in the AR of the as-spun fibres was observed. Short fibres with average AR of 15 were produced from PMSQ2 solution in 3:2∈v/v dimethylsulphoxide:2-nitropropane. The average AR of short fibres spun from PMSQ2 solution in 2:3∈v/v methanol:propanol was 31. Also PMSQ1 in both of the above-mentioned binary solvent systems produced long continuous fibres with AR >3000 under the same spinning conditions.