Hybrid Hemp Particles as Functional Fillers for the Manufacturing of Hydrophobic and Anti-icing Epoxy Composite Coatings

Abstract

The development of hydrophobic composite coatings is of great interest for several applications in the aerospace industry. Functionalized microparticles can be obtained from waste fabrics and employed as fillers to prepare sustainable hydrophobic epoxy-based coatings. Following a waste-to-wealth approach, a novel hydrophobic epoxy-based composite including hemp microparticles (HMPs) functionalized with waterglass solution, 3-aminopropyl triethoxysilane, polypropylene-graft-maleic anhydride, and either hexadecyltrimethoxysilane or 1H,1H,2H,2H-perfluorooctyltriethoxysilane is presented. The resulting epoxy coatings based on hydrophobic HMPs were cast on aeronautical carbon fiber-reinforced panels to improve their anti-icing performance. Wettability and anti-icing behavior of the prepared composites were investigated at 25 °C and −30 °C (complete icing time), respectively. Samples cast with the composite coating can achieve up to 30 °C higher water contact angle and doubled icing time than aeronautical panels treated with unfilled epoxy resin. A low content (2 wt %) of tailored HMPs causes an increase of ∼26% in the glass transition temperature of the coatings compared to pristine resin, confirming the good interaction between the hemp filler and epoxy matrix at the interphase. Finally, atomic force microscopy reveals that the HMPs can induce the formation of a hierarchical structure on the surface of casted panels. This rough morphology, combined with the silane activity, allows the preparation of aeronautical substrates with enhanced hydrophobicity, anti-icing capability, and thermal stability.

Eco-friendly composites with specific functional properties

“…The successful functionalization of hemp microfibrils was also assessed by ATR-FTIR analysis, as shown in Figure 4. permission from [14]). The highlighted signals on ATR-FTIR spectrum (Figure 4(a)) confirm the effective functionalization of the hemp fiber particles:…”

“…Procedure for the preparation of hydrophobic hemp particles (HEMPP) (reprinted with permission from [14]).…”

“…All the coatings were cured for 24 hours at 60 °C and post-cured for 4 hours at 80 °C. The functionalization and fabrication of hemp particles and the manufacturing of fiber-reinforced epoxy composite coatings are well described in [14]. All the investigated samples are listed in Table 1.…”

“…Atomic force microscopy (AFM) was used to evaluate the surface roughness of pristine epoxy and hemp-epoxy coatings. For all the specimens, the roughness average (Ra) and the root mean square roughness (Rq) parameters were evaluated according to equations shown in [14]. Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) were carried out to assess the thermal behavior of pristine epoxy and hemp-epoxy coatings.…”

“…In the present study, thermosetting composite coatings with enhanced hydrophobicity were deposed by casting on carbon-fiber-reinforced (CFR) polymer panels typically employed for aircraft structures. The novelty of this work was to demonstrate the possibility of using waste hemp functionalized particles to obtain innovative hemp-epoxy coatings with improved hydrophobicity and anti-icing performances for aircraft applications [14]. Specifically, morphological, structural, thermal and hydrophobic/anti-icing properties of hemp composite coatings are discussed.…”