Stable superhydrophobic coatings using PVDF-MWCNT nanocomposite

Thermally stable superhydrophobic coatings have been prepared using polyvinylidene fluoride (PVDF)-multiwalled carbon nanotubes (MWCNTs) by spray coating method. The effects of MWCNT (0-66 wt.%) and temperature (300-623 K) on wettability have been studied. A transformation from hydrophobic to superhydrophoic state has been achieved with increase of CNT content. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) studies reveal that with increase in CNT content, α-phase of PVDF decreases suggesting that MWCNT has strong effect on the phase separation of PVDF. Field emission scanning electron microscopy (FESEM) studies show that the coatings have rough surface with porous structure. With increase in MWCNT content the protrusion like structures decrease that leads to micro/nano scales. The coatings are thermally stable up to 573 K exhibiting superhydrophobicity and thereafter transformed to superhydrophilic state at 623 K. Energy dispersive X-ray spectroscopy (EDXS) analysis shows the absence of fluorine after annealing at 623 K suggesting decomposition of PVDF. X-ray photoelectron spectroscopy (XPS) of C1s and F1s core levels in as-deposited PVDF-MWCNT coating show the presence of CF2 related species. Concentration of fluorine drastically decreases after heat treatment of the coating at 623 K. The main advantage of the present method is feasibility for application over large area and the coatings are stable up to 573 K.