Processing and characterization of polyethersulfone wet-spun nanocomposite ﬁbres containing multiwalled carbon nanotubes J. Bouchard a,b , A. Cayla a,b, *, S. Odent b , V. Lutz c , E. Devaux a,b , C. Campagne a,b a University of Lille Nord de France, F-59000 Lille, France b ENSAIT, GEMTEX, F-59100 Roubaix, France c INSA de Lyon, CNRS UMR 5223, Ingénierie des Matériaux Polymères, Villeurbanne, F-69622 Lyon, France A R T I C L E I N F O Article history: Received 7 February 2016 Received in revised form 10 April 2016 Accepted 11 April 2016 Available online 26 April 2016 Keywords: Fibres Carbon nanotubes Polyethersulfone Electrical Properties Heat treatment A B S T R A C T Novel semi-conductive ﬁbres from multiwalled carbon nanotubes (MWCNT) based-polyethersulfone (PES) have been produced by wet spinning insight of incorporation in composite matrix. N-methyl-2- pyrrolidone (NMP) was chosen as dispersing medium for MWCNT by sonication and as solvent for PES. MWCNT reinforced-PES ﬁbres were spun into water coagulation bath with an observed instantaneous liquid-liquid demixing. After washing and drying steps, ﬁbres are either directly characterized or annealed at 250  C during 15 min and 24 h prior to characterization. Scanning electron microscope (SEM) micrographs performed in each conﬁguration disclose presence of macrovoids, pores and empty spaces inside ﬁbres before thermal annealing whereas after thermal annealing, ﬁbres display a cohesive and continuous morphology. A signiﬁcant mechanical properties improvement of the wet-spun ﬁbres is noticed by rising annealing time. Transmission electron microscope (TEM) investigations have also been carried out and reveal a two phases microstructure in unannealed ﬁbres with a separation between a PES-rich continuous phase and NMP-rich nodules containing exclusively MWCNT. TEM images suggest also thermal annealing process allows solvent evaporation, MWCNT aggregation and a conductive nanoﬁllers network formation in PES nanocomposite ﬁbres. Electrical measurement in unannealed ﬁbres indicate a deﬁciency of conductive character between 0.25 and 2 wt.% MWCNT whereas a lowering electrical percolation threshold is achieved in ﬁbres by increasing annealing time, around 1.5 and 1 wt.% MWCNT for respectively a 15 min and 24 h thermal annealing. Inﬂuence of MWCNT sonication duration on electrical conductivity is also examined showing a gradually reduction of ﬁbres' electrical conductivity by dispersion time increasing until losing their semi-conductive state. A dispersion analysis let suppose that a whole MWCNT agglomerates network is split in smaller but denser clusters which are dispersed and taken away from each other during sonication, which causes the conductive path rupture. ã 2016 Elsevier B.V. All rights reserved. 1. Introduction Nowadays, the whole aerospace industry is dealing with major challenges such as cost savings, weight reduction and improved durability. The mutation from metallic to composite parts is an important key for reducing costs and the environmental imprint caused by transport. However, this turn to composites causes technical issues such as for lightning strike protection or electromagnetic interference (EMI) shielding due to low electrical conductivity, low toughness, and poor transverse and interlaminar properties of the composites [1]. Solutions have been found, such as the presence of metallic mesh on the surface for the electrical conductivity issue, but this is to the detriment of weight-saving requirements. The development and incorporation of new material combinations in composite through innovative synergies appear to be an adequate solution. Thus, there is growing demand from the aerospace industry to develop carbon nanotube (CNT)-based materials. These novel materials have to be produced in the form of ﬁlm, yarn or even ﬁbre based on high-performance engineering thermoplastics for CNT pre-orientation and alignment [2] with a view to their insertion in composite matrices. Since their identiﬁcation by Iijima [3], CNT have continued to draw the attention of industry and science owing to their exceptional mechanical and electrical properties [4]. Their extraordinarily high aspect ratio allows the material properties to be enhanced with a low percentage of incorporated nanoﬁllers compared to other carbon ﬁllers, such as carbon black [5]. To form CNT-based ﬁbres, the nanoﬁllers are often incorporated in * Corresponding author. E-mail address: aurelie.cayla@ensait.fr (A. Cayla). http://dx.doi.org/10.1016/j.synthmet.2016.04.007 0379-6779/ã 2016 Elsevier B.V. All rights reserved. Synthetic Metals 217 (2016) 304–313 Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.else vie r.com/locat e/synme t