Improved thermal stability of cycloaliphatic epoxy resins by incorporation of OCTA-functional poss

Carbon fibre reinforced polymer (CFRP) composites employing epoxy matrices have been recently used in a number of space applications, especially in structural components of spacecraft in low Earth orbit (LEO). However, in this region, CFRP structures are subjected to degradation by highly energetic ultraviolet radiation. Aromatic epoxies, which are commonly used, contain rigid phenyl rings, which confer higher mechanical properties and thermal stability, but these structural moieties absorb UV radiation strongly. In contrast, fully saturated cycloaliphatic epoxy resins are better suited for outdoor exposures, since they are poor chromophores with lower intensity UV absorption. In this work, we report on incorporation of an octa-functional polyhedral oligomeric silsesquioxane (POSS) reagent into a cycloaliphatic epoxy and discuss the influence of this hybridization on the thermal-degradation mechanism. POSS has been added in various concentrations of 5, 10, 15 and 20 wt. % and the cycloaliphatic epoxy was cured with either an anhydride or a cycloaliphatic diamine. The thermal and thermomechanical properties of each cured polymer were evaluated using thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The findings of this study contribute to development of advanced polymer matrix materials for extreme operation environments, such as LEO.