Multifilament fibres of poly(ɛ-caprolactone)/poly(lactic acid) blends with multiwalled carbon nanotubes as sensor materials for ethyl acetate and acetone

Abstract

Conductive poly(ɛ-caprolactone) (PCL) + 4% multiwalled carbon nanotubes (MWCNTs)/poly(lactic acid) (PLA) = 50/50 wt% blend multifilament fibres were melt-spun and a woven textile was made by a handloom with the conductive fibres in weft direction. The fibres were tested for cyclic liquid sensing in ethyl acetate and acetone as two moderate solvents and in ethanol as a poor solvent. The liquid sensing responses, namely the relative resistance changes R rel relating the resistance change to the initial resistance of the samples on contact with ethyl acetate and acetone, were fast ( R rel higher than 16 after 100 s), with high amplitudes ( R rel higher than 23 after 500 s), and well reproducible. At the same time, the fibres were resistant against these solvents. The response to ethanol was also reproducible, however, very slow and with low amplitude. PLA was found to crystallize during the immersion process, whereas in PCL the crystalline domains transformed into amorphous ones as studied by Wide Angle X-ray Diffraction. The crystallization of PLA does not influence negatively the liquid sensing properties which can be assigned to the finding that the MWCNT are predominantly localized in the PCL phase as confirmed by Scanning Electron Microscopy. In the final step, a textile based on those fibres was prepared and its sensing behaviour was investigated on ethyl acetate and acetone clearly showing that such textiles are suitable to detect these solvents.