TiO2 reinforced high-performance epoxy-co-polyamide composite coatings

Abstract

Epoxy-based protective coatings for outdoor and marine applications are commonly used to protect metals and alloys, and architectural elements against the environmental impact. An epoxy-co-polyamide (EP-PA) polymer is synthesized by reacting pre-polymers: epoxy and polyamide resins. TiO2 nanoparticles of different sizes are embedded into EP-PA copolymer to form composite coatings on the Teflon substrate, referred to as EP-PA/TiO2. TiO2 content is varied from 0.1 to 1.0 wt.% and the electrical, thermal, and mechanical performance of composites is analyzed. Both EP-PA polymer and EP-PA/TiO2 composite coatings are characterized by FTIR spectroscopy and electron microscopy. EP-PA/TiO2 composites exhibit a uniform distribution of individual TiO2 nanoparticles in the EP-PA matrix at low TiO2 content, while some aggregates are observed at the higher TiO2 content. The size effect of TiO2 nanoparticles is also demonstrated by clear differences in the surface topography, size distribution, extent of agglomeration, and surface roughness of the EP-PA/TiO2 composites. TiO2 nanoparticles have lower surface energy and therefore, increase the hydrophobic character of the composite coatings that is revealed by the increasing water droplet contact angle. The surface resistivity of EP-PA/TiO2 composites decreased with the increasing TiO2 content, while thermal degradation temperatures are improved by 100 K (15.7 %) compared to neat EP-PA polymer. The mechanical properties such as yield strength and Young’s modulus are also enhanced by 56.9 % and 32.7 %, respectively at 1.0 wt.% TiO2 loading, while the toughness of EP-PA/TiO2 composites is comparable to the neat polymer. The remarkable enhancement in the hydrophobic character, electrical conductivity, thermal stability, and mechanical performance of EP-PA/TiO2 composites at low TiO2 content (1.0 wt.%) is achieved by the small size, high surface area, and excellent dispersion of nanoparticles in the polymeric matrix. The simultaneous improvement in properties suggests EP-PA/TiO2 composites useful as protective coatings for a variety of applications in the harsh environment.