Effect of the POSS–Polyimide nanostructure on its mechanical and electrical properties

Nanocomposite films consisted of Polyhedral Oligomeric Silsesquioxane (POSS) filler in a Polyimide (PI) matrix were prepared. The effect of the nanocomposites’ structure on its mechanical and electrical properties was evaluated with respect to survival in the low Earth orbit (LEO) environment. The POSS–PI structure consists of POSS nano-aggregates formed in the bulk and on the surface. The aggregates’ size and distribution are POSS content-dependant. The fracture mechanism during hypervelocity impact at extreme temperature conditions was studied. The hypervelocity impacts of the POSS–PI films result in a brittle fracture, compared to ductile fracture in the case of PI, and in formation of radial cracks. A model based on formation and coalescence of voids around the aggregates, when load is applied, is suggested to explain the effect of the POSS content on the POSS–PI fracture mechanism. The size and density of the POSS aggregates also affect the nanocomposite’s volume electrical resistivity. An inverse dependence exists between the POSS aggregates’ surface density and the nanocomposites’ volume electrical resistivity.