Self-cleaning performance of polyvinylidene fluoride-zinc oxide composite coatings for civil and industrial applications

Abstract

Synthesis of super/hydrophobic solid surfaces is an active area of research in recent years because it forms the basis for multidisciplinary applications such as agricultural, environmental, and biological processes, such as the prevention of the adhesion of dust to antennas and windows, self-cleaning traffic indicators, waterproof and corrosion resistance coatings. Inspired by the self-cleaning behaviour of lotus leaves in nature, a simple coating method was developed in the present work to facilitate the bionic creation of super-hydrophobic surfaces on various substrates. Due to the chemical stability and flexibility, polyvinylidene fluoride (PVDF) membranes are widely used as the topcoat of architectural membrane structures, roof materials of vehicle, and tent fabrics. Further modified PVDF membrane with superhydrophobic property may be even superior as the coating layer surface. The present study aims to provide a better understanding of the effects that the addition of zinc oxide (ZnO) nanoparticles would have on the hydrophobic properties of PVDF using one-step facile spray-coating process. The surface was prepared through spray coating of a mixture of PVDF and ZnO nanoparticles on aluminum substrate. Stearic acid was added to improve the dispersion of ZnO. The Taguchi method was used to rank several factors that may affect the superhydrophobic properties in order to formulate the optimum conditions. The crystallinity and morphology of PVDF-ZnO membranes were determined by FTIR and SEM. The results of the Taguchi method indicate that the ZnO and Stearic acid contents were the parameters making significant contribution toward improvement in hydrophobicity of PVDF composites. As the content of ZnO nanoparticles increased, the values of water contact angle increased, ranging from 122o to 159o, while the contact angle hysteresis and sliding angle decreased to 3.5° and 2.5°, respectively. The SEM results show that hierarchical micro-nanostructure of ZnO plays an important role in the formation of the superhydrophobic surface. FTIR results showed that, in the absence or present ZnO nanoparticles, the crystallization of the PVDF occurred predominantly in the ß-phase. The coatings proved to be an especially useful class of liquid repellent materials due to their low surface energy, and the roughness characteristics of the aggregates.