Nanocomposite films of poly(vinylidene fluoride) filled with polyvinylpyrrolidone-coated multiwalled carbon nanotubes: Enhancement of ß-polymorph formation and tensile properties

To improve interactions between carbon nanotubes (CNTs) and poly(vinylidene fluoride) (PVDF) matrix, multiwalled CNTs (MWCNTs) were successfully coated with amphiphilic polyvinylpyrrolidone (PVP) using an ultrasonication treatment performed in aqueous solution. It was found that PVP chains could be attached noncovalently onto the nanotubes' surface, enabling a stable dispersion of MWCNTs in both water and N,N-dimethylformamide. PVP-coated MWCNTs/PVDF nanocomposite films were prepared by a solution casting method. The strong specific dipolar interaction between the PVP's carbonyl group (C?O) and the PVDF's fluorine group C?F2 results in high compatibility between PVP and PVDF, helping PVP-coated MWCNTs to be homogenously dispersed within PVDF. Fourier transform infrared and X-ray diffraction characterization revealed that the as-prepared nanocomposite PVDF films exhibit a purely beta-polymorph even at a very low content of PVP-wrapped MWCNTs (0.1 wt%) while this phase is totally absent in the corresponding unmodified MWCNTs/PVDF nanocomposites. A possible mechanism of beta-phase formation in PVP-coated MWCNTs/PVDF nanocomposites has been discussed. Furthermore, the tensile properties of PVDF nanocomposites as function of the content in PVP-coated MWCNTs were also studied. Results shows that the addition of 2.0 wt% of PVP-coated MWCNTs lead to a 168% increase in Young's modulus and a 120% in tensile strength. POLYM. ENG. SCI., 2013. (c) 2012 Society of Plastics Engineers