Hypervelocity impact and outgassing tests on ethylene co-methacrylic acid ionomers for space applications

The ability of a material to self-repair is particularly important in remote or hostile environment applications, where an external intervention is nearly impossible. For example, the development of self-healing (SH) materials for space applications could dramatically improve spacecraft performances and liability, with significant enhancement of mission duration. A number of copolymeric ionomers have been recognized to present self-healing capability under defined ballistic conditions and have risen considerable interest by researchers. On the other hand, when exposed to a vacuum environment for long period, polymers may exhibit considerable mass reduction due to volatile diffusion and loss; this can significantly affect physical and mechanical properties, thus preventing their employment in space applications. This work aims to give a preliminary evaluation of possible employment of polyethyleneco-methacrylic acid (EMAA) based ionomers in space environment. The SH capability was studied through hypervelocity impact tests in different experimental configurations, in order to simulate the collision events with micrometeoroids or debris typical of space environment. The healing efficiency was evaluated by leakage tests and by observation of the impact area with a scanning electron microscope. Thermal outgassing tests were performed to explore the material behaviour in conditions similar to those of space environment. Using a high vacuum chamber, specimens were exposed to a vacuum environment; thermal cycles were also applied to favour the outgassing phenomena. Quite limited mass losses were detected after the tests.