Electrically conductive crystalline polylactide nonwovens obtained by electrospinning and modification with multiwall carbon nanotubes

Polylactide nonwovens were electrospun from solutions and then crystallized, one in alpha-form, and another, S-PLA, made of poly(L-lactide) and poly(D-lactide) 1:1 blend, in scPLA crystals with high melting temperature, close to 220 degrees C. To make the nonwovens electrically conductive, they were coated with multiwall carbon nanotubes (MWCNT) by padding and dip-coating with an aqueous dispersion of MWCNT. The electrical conductivity evidenced the formation of the electrically conductive MWCNT network on the fiber surfaces. Depending on the coating method, the surface resistivity (Rs) of S-PLA nonwoven of 1.0 k omega/sq and 0.09 k omega/sq was reached. To study the effect of surface roughness, before the modification the nonwovens were etched with sodium hydroxide, which additionally made them hydrophilic. The effect of etching depended on the coating method and led to an increase or decrease of Rs, in the case of padding or dip-coating, respectively. All MWCNT-modified nonwovens, unetched and etched, were hydrophobic with water contact angles of 138-144 degrees. Scanning electron microscopy corroborated the presence of MWCNT on the fiber surfaces. Impedance spectroscopy confirmed the dominant role of the network of MWCNT direct contacts on the electrical properties of MWCNT-modified nonwovens in a broad frequency range.