Siloxane-epoxy composite coatings for enhanced resistance to large temperature variations

Abstract The practical applications of epoxy coatings are still limited due to their high brittleness and vulnerability to extreme temperature variations. Here siloxane-epoxy composite with good resistance to alternating heat and cold was obtained by a simple sol-gel preparation of 3-aminopropyl triethoxysilane (APTES)-modified epoxy resin without using additional curing agent. The effect of the blend ratio of APTES on enhanced resistance to alternating heat and cold properties of composite material was investigated. Weight loss test by immersion in xylene and characterization by differential scanning calorimetry and Fourier transform infrared spectroscopy confirmed successful modification of epoxy resin. The char yield (about 28 %) at 600 °C of siloxane-epoxy composite containing 37.5 wt% APTES was higher than the reference epoxy sample (about 9.1 %), as identified by the thermogravimetric analysis. Meanwhile, electrochemical impedance spectroscopy showed that the |Z|0.01 Hz value (2.58 × 105 Ω cm2) of 37.5 % modified epoxy resin-coated sample is much larger than that (4.13 × 104 cm2) of the reference epoxy coating, meaning the siloxane-epoxy composite provides effective corrosion protection. Moreover, it maintained the mechanical properties and protection ability after high (25 °C) and low temperature (−30 °C) alternation resistance test for 10 days. SEM imaging confirmed the APTES-modified epoxy resin composite showed better extreme low temperature resistance than the reference sample.