A nanocellular PVDF–graphite water-repellent composite coating

Abstract

We have developed a cost-effective method for the preparation of a porous superhydrophobic polyvinylidene fluoride (PVDF)/graphite composite with an induced nanocellular patterned surface. The microstructure of the surface was investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) and the interaction between graphite and PVDF by Raman spectroscopy. The PVDF/graphite powder contained spherulites and had a roughened nanocellular surface with a water contact angle of 145° and roll-off angle of 5°. However, after coating the PVDF/graphite powder the nanocellular-like structure had a water contact angle of 153° with roll-off angle of 4°. The dry composite was self-cleaning by virtue of the interaction of a non-solvent (methanol) with a PVDF/graphite powder suspension in N,N-dimethylformamide (DMF). It was noticed that prolonged quenching altered the surface morphology of the dry composite. To illustrate the improvement of water repellency using PVDF composites, we also studied the mechanism of formation of the nanocellular structure with a view to its industrial application. In addition, in the case of PVDF porous materials, the inclusion of tiny amounts of graphite powder in the composite not only promoted crystallization of the PVDF, but also modified the surface texture and roughness to give superhydrophobicity.