Synthesis and characterization of cardanol-based epoxy coatings for anti-icing applications

Abstract

Hydrophobic coatings are water-repellent and can be used for anti-icing, easy-cleaning and anti-corrosion applications. Epoxy resins are precursors with a broad range of functionalities and are commonly used by the adhesives, high performance composites, insulations and protective coatings industries. Epoxy resins are hydrophilic in nature, making the fabrication of hydrophobic coatings a challenge. Moreover, conventional epoxy resins based on bisphenol A (BPA) are known to interfere with the hormonal system of humans and animals. The demand for environmental sustainability has motivated coatings industries to reduce or eliminate the usage of BPA and look for bio-based epoxy resin alternatives.

This project mainly focuses on the preparation of hydrophobic coatings using a viable bio-based precursor like cardanol which is extracted from cashew nutshell liquid (CNSL). In this study, cardanol-based coatings were developed using NC514S as the epoxy resin and citric acid as the curing agent. This report also details the synthesis methodology for the development of the coatings. The coatings were cured with various organic additives (Polydimethylsiloxane, octanoic acid and 1,2-epoxydecane). The surface, mechanical and thermal properties of the cardanol-based coatings were characterized comprehensively using Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), contact angle goniometer and cold climate chamber. Furthermore, the chemical bonding information and curing degrees were studied through Fourier Transform Infrared (FTIR) Spectroscopy. A comparative study was also performed on the wettability and thermal properties of the cardanol-based coatings to investigate the effects of organic additives. The cardanol-based coatings were hydrophobic in nature and NC514S-CA-PDMS coating had the best hydrophobicity and anti-icing performance. The study concludes with a brief discussion on some limitations related to the findings in order to provide a future outlook on investigations of hydrophobic cardanol-based coatings for anti-icing applications.