Covalent grafting of unfunctionalized pristine MWCNT with Nylon-6 by microwave assist in-situ polymerization

Covalent grafting of nylon-6 (Ny-6) and pristine multi-walled carbon nanotubes (MWCNT-P) was performed in-situ via microwave assist polymerization (MAP) of ε-caprolactam and 6-aminocaproic acid at different power and time conditions. The results showed that the microwave dielectric heating of the MWCNT-P activates the nanotube vacancies to react with the amine group of 6-aminocaproic acid at 175 °C. When the reaction temperature reaches 230 °C, Ny-6 polymerization ensues, simultaneously, with insertion of Ny-6 chains on the amine-activated MWCNT to obtain a nanohybrid, MWCNT-Ny, with a grafted Ny-6 coating of 14 nm. The hybridization reaction therein affects the entire polymerization process and the molecular weight and yield of both the hybrid and Ny-6. Raman, XPS and electrical conductivity data for the MWCNT-Ny films show that the nanotube structure remains intact in the films which display an electrical surface conductivity range of 0.47–0.06 S/m. The compatibility and dispersion of the MWCNT-Ny nanohybrid in Ny-6, as observed by crystallization and fusion of the so-formed hybrid polymer nanocomposite, HPNC, exceed those obtained by conventional methods of preparation using ultrasound and functionalized nanotubes. [Display omitted] •Dielectric heating of MWCNTs produces the polymerization and hybridization reaction.•Covalent grafting of Nylon-6 chains on unfunctionalized MWCNT.•MWCNTs accelerate the heating rate of polymerization processes.•The hybridization of MWCNTs affects the molecular weight and polymer conversion.•High electrical conductivity of MWCNT-Nylon 6 hybrids.