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Ethylene-co-methacrylic acid (EMAA) based ionomers have thermo-mechanical properties strongly dependent on neutralization level of acid groups. Research revealed also how these materials are able to heal after ballistic impacts. In order to better understand the role of neutralization level on the Self-Healing (SH) behaviour, mechanical and ballistic tests on EMAA copolymers, neutralized with different amount of Na ions, were performed in different experimental conditions. The SH capability was studied by shooting bullets at low velocity (180 m/s) and mid velocity (400 m/s); different testing conditions such as sample thickness and bullet diameter were examined. In all impact tests, spherical projectiles were used. These experiments allowed to define a critical ratio between sample thickness and bullet diameter below which the SH behaviour does not appear. After ballistic damage, the healing efficiency was evaluated by applying a pressure difference through tested samples. Subsequently, morphology analysis of the impacted areas was made observing all tested samples by Scanning Electron Microscope (SEM). These analysis revealed different characteristic features in the damaged zones of tested polymers impacted at different projectile speed. Obtained results show how the Na ions content influences the SH capability; in particular the EMAA copolymer with the highest Na neutralization level does not show a complete hole closure after low velocity impact test. Conversely, increasing projectile speed, all the polymers exhibit nearly the same SH behaviour.

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.

Ethylene-co-methacrylic acid (EMAA) based ionomers have thermo-mechanical properties strongly dependent on neutralization level of acid groups. Research revealed also how these materials are able to heal after ballistic impacts. In order to better understand the role of neutralization level on the Self-Healing (SH) behaviour, mechanical and ballistic tests on EMAA copolymers, neutralized with different amount of Na ions, were performed in different experimental conditions. The SH capability was studied by shooting bullets at low velocity (180 m/s) and mid velocity (400 m/s); different testing conditions such as sample thickness and bullet diameter were examined. In all impact tests, spherical projectiles were used. These experiments allowed to define a critical ratio between sample thickness and bullet diameter below which the SH behaviour does not appear. After ballistic damage, the healing efficiency was evaluated by applying a pressure difference through tested samples. Subsequently, morphology analysis of the impacted areas was made observing all tested samples by Scanning Electron Microscope (SEM). These analysis revealed different characteristic features in the damaged zones of tested polymers impacted at different projectile speed. Obtained results show how the Na ions content influences the SH capability; in particular the EMAA copolymer with the highest Na neutralization level does not show a complete hole closure after low velocity impact test. Conversely, increasing projectile speed, all the polymers exhibit nearly the same SH behaviour.

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.