A methodology to orient carbon nanotubes in a thermosetting matrix

A new procedure for the alignment of carbon nanotubes in a thermosetting matrix is proposed in this study. The two-step approach is based on (i) the alignment of carbon nanotubes (CNTs) in thermoplastic fibres by electrospinning and (ii) the transfer of these nanocompositefibres into a reactive thermosetting resin, in which they are easily soluble. After fibre dissolution, the CNTs remain aligned in the cured thermosetting matrix. The proof of concept is demonstrated by producing electrospunpolymethyl methacrylate (PMMA) fibres filled with single wall carbon nanotubes (SWCNTs) in the form of unidirectional tape, which are then solubilised into a vinylester (VE) matrix. The PMMA is easily dissolved by the styrene present in the VE resin, leaving SWCNTs aligned in the cured VE network, as confirmed by Raman spectroscopy studies. A 50% increase in elastic modulus (SWCNT 1.3 wt.%) has been obtained by dynamic mechanical analysis carried out in tensile mode at 1 Hz. Thanks to its ability to orient carbon nanotubes in a thermosetting matrix, the proposed method can be exploited also to transfer oriented nanofillers into continuous fibre composites, thus obtaining multiscale or hierarchical composites.