Eco-friendly composites with specific functional properties

The development of sustainable hydrophobic composite coatings is of high interest for aircraft applications. Currently, the use of natural derived functionalized microparticles as filler to obtain hydrophobic epoxy-based coatings was not deeply investigated. In this scenario, a novel hydrophobic epoxy-based composite including waste hemp microparticles functionalized with silica layer, 3-aminopropyltriethoxysilane, polypropylene-graft-maleic anhydride and silanes (hexadecyltrimethoxysilane and 1H,1H,2H,2H- Perfluorocotyltriethoxysilane) is presented. The resulting coating was casted on typical aeronautical panel, based on carbon-fiber-reinforced polymers, to achieve an improved hydrophobicity and anti-icing property induced by functionalized hemp microparticles. The wettability and anti-icing property were investigated. Compared to unfilled epoxy resin, the obtained composite coating achieved a greater water contact angle of 30° and doubled increase in icing time. Despite the low content (2 wt.%) of hemp particles, DSC analysis displayed a relevant increase in Tg value, confirming an efficient interaction between the epoxy matrix and the functionalized hemp filler. AFM analysis proved how the presence of hemp filler leads to an increase in roughness due to the hierarchical structure formed by the long chains of silane molecules. The combination of silane activity and rough morphology allows the development of hemp composite coatings with enhanced hydrophobicity, anti-icing behavior and thermal stability for aircraft applications.