Comparison of the effects of graphene and nanoclay nanosheets on crystalline structure of polyvinylidene fluoride

An extensive review of the literature showed that both graphene and Cloisite ۳۰B nanosheets are widelyemployed to modify the crystalline structure and piezoelectic properties of polyvinylidene fluoride (PVDF).Due to the similarity in the geometry of these nanoparticles a comparative study is reported to find the stemsof difference in their effects on crystalline structure of PVDF. Scanning electron microscopy (SEM) of thesecomposites showed that large and wide graphene particles are dispersed in PVDF matrix whereas theirthickness is well below ۱۰۰ nanometers. Meanwhile, a careful inspection of SEM micrographs of Cloisite ۳۰Bloaded composites revealed existence of smaller particles with almost the same particles thicknesses. Bothtechniques of Fourier transform infrared (FT-IR) spectroscopy and wide angle X-ray diffraction (WXRD)witnessed changes in the crystalline structure of PVDF. The overall finding was that Cloisite ۳۰B improvesthe polar beta phase of PVDF crystals, whereas a revers effect was found in the presence of graphenenanosheets. These observations were accounted for by differences in surface geometry and surface free energy(surface tension and interfacial tension). Based on the data available for surface properties of these twonanosheets it was found that surface properties of Cloisite ۳۰B is very close to those of PVDF, whereas thesurface properties of graphene are far from those of PVDF. Also a lower interfacial tension was found to beactive in PVDF-Cloisite ۳۰B system compared to that operative in PVDF-graphene system. An intimateinterface along with proper surface texture led to higher content of PVDF’s beta crystals in case of Cloisite۳۰B nanocomposite.

Keywords:

PVDF , Cloisite ۳۰B , Graphene , surface free energy , Morphology