Melt processing and mechanical property characterization of high-performance poly(ether ether ketone)–carbon nanotube composite

Poly(ether ether ketone) (PEEK)–multiwall carbon nanotube (MWCNT) composites were fabricated via injection moulding and subsequently characterized by means of microstructural, morphological, thermal and mechanical investigations. Scanning electron microscopy observations demonstrated a uniform distribution of MWCNTs within the matrix, while tensile tests revealed an unexpected high strain at rupture (up to 140%), despite the insertion of MWCNTs ensuring an increase of modulus and strength. Differential scanning calorimetry showed that MWCNT addition did not cause any significant increase in crystallinity of PEEK, and therefore it was concluded that the nanotubes acted as a confinement of polymer chains, hindering chain mobility. X-ray diffraction showed the typical PEEK and MWCNT peaks, without evidencing the presence of any different phase. The strain at fracture of samples tested after annealing returned to values comparable with those of neat PEEK