Fluorinated-polyhedral oligomeric silsesquioxane (F-POSS) functionalized sepiolite nanostructures for developing epoxy nanocomposites with tailored crosslinking, antifouling, and self-cleaning properties

Developing multifunctional epoxy composites with tailored properties supports energy systems, especially oil and gas industries. We report synthesis of 3D fluorinated-polyhedral oligomeric silsesquioxanes (F-POSS) nanoparticles (NPs) co-condensed on the surface of 2D sepiolite (SEP) nanoclays, and dispersed it within an epoxy resin to facilitate curing kinetics of epoxy-amine system. A catalytic effect was realized, supporting excellent cure index, according to the kinetic models employed. Friedman model suggested double values of activation energy for composites (54.32 KJ/mol for Epoxy/SEP and 50.73 KJ/mol for Epoxy/F-POSS@SEP) compared to blank (reference) resin (26.12 KJ/mol). Nanostructure of F-POSS@SEP observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy, demonstrating co-condensation of F-POSS and SEP nanoclays. Nanotribology tests suggested higher surface properties. Hardness of epoxy was 0.373 GPa; when modified with 5 and 10 wt% of F-POSS@SEP it resulted in 0.41 and 0.38 GPa, respectively. The reduced modulus was 4.53 GPa for epoxy, while 5.1 and 5.0 GPa for 5 and 10 wt% F-POSS@SEP, respectively. The free surface of composites was studied by SEM and contact angle techniques. F-POSS/SEP nanostructure populated at air-free surface, as a consequence of natural migration of fluorine. Contact angle measurements were performed in dynamic tests, showing increased hydrophobicity of thermoset composites, where an outstanding antifouling behavior was correspondingly achieved. Sliding angles diminished from 19.1° for epoxy to 8.1° and 5.0° for 5 and 10 wt.% of F-POSS@SEP, respectively. Accordingly, fouling of 5 and 10 wt.% F-POSS@SEP modified composites was 42% lower than that for epoxy. Self-cleaning resulted 18% and 16% higher for 5 and 10 wt.% F-POSS@SEP nanocomposites, respectively, compared to epoxy. These results are promising to contribute high-performance materials for the energy production sector.

Highlights

• Developed fluorinated polyhedral oligomeric silsesquioxanes (F-POSS)/sepiolite.
• Detected catalytic effect of F-POSS/sepiolite on epoxy-amine cross-linking kinetics.
• Fouling decreased by 42%, whereas recovery increased 10-fold by cleaning surface.
• Self-cleaning properties demonstrated by up to 74% reduction in water slip angle.
• Potential use in pipelines to prevent paraffin deposits due to antifouling properties.