Study on Atomic Oxygen Exposure and Hard Particle Impact of Polyimide Nanocomposites

Atomic oxygen (AO) exposure and hard microparticle impact on polyimide nanocomposites were performed by a ground-based magnetoplasmodynamic accelerator and electrostatic accelerator, respectively. The computer simulation of the AO erosion of polyimide nanocomposites was carried out with Monte Carlo method. It is found that the polyimide nanocomposites are significantly more durable to AO exposure than the pure polyimide material. Besides, in the case of combined hard microparticle impact and AO exposure, the regions around craters created by hard microparticle impact are etched more intensively than the undamaged areas of the polyimide nanocomposite sample surface.

Atomic Oxygen Adaptability of Flexible Kapton/Al2O3 Composite Thin Films Prepared by Ion Exchange Method

Polyimide film (Kapton) is an important polymer material used for the construction of spacecrafts. The performance of Kapton can be degraded for atomic oxygen erosion in space. Commonly used atomic oxygen protective layers have issues such as poor toughness and poor adhesion with the film. In this paper, Kapton/Al2O3 nanocomposite films were prepared via an ion exchange method, and the optical properties, mechanical properties, and mechanisms for the change in the mass and microstructure, before and after atomic oxygen exposure, were analyzed. The results show that the deposition of the Kapton/Al2O3 surface nanocomposite film prepared via the ion exchange method has no obvious effects on the internal structure and optical transmittance of the Kapton film matrix. The tensile strength and elongation of the prepared film were much higher than those of the pure Kapton film, demonstrating its good flexibility. Scanning electron microscope (SEM) analysis showed that the etching pits had a carpet-like morphology on the composite film surface and were relatively small after atomic oxygen erosion. In contrast with the C–C bond rupture in the oxydianiline (ODA) benzene in Kapton films, the Kapton/Al2O3 nanocomposite film mainly destroyed the C=C bond in the pyromellitic dianhydride (PMDA) benzene ring. On exposure to an atomic oxygen environment for a short period, the Kapton/Al2O3 nanocomposite film exhibited improved atomic oxygen erosion resistance because the Al2O3 layer inhibited atomic oxygen diffusion. With increasing atomic oxygen exposure time, the atomic oxygen diffused into the Kapton matrix via the pores of the Al2O3 layer, causing damage to the substrate. This resulted in a detachment of the surface Al2O3 layer and exposure of the Kapton matrix, and thereby the atomic oxygen resistance was decreased. The applicability of the ion exchange mechanism of trivalent Al element on the surface modification of the polyimide is explored in this study. The behavior of the Kapton/Al2O3 composite film under the atomic oxygen environment of space is investigated, which provides the basis for studying the effects of atomic oxygen on the flexible protective Kapton film.

Effects of atomic oxygen on epoxy-based shape memory polymer in low earth orbit

Atomic oxygen is a dominant component of the low earth orbit and can erode most spacecraft polymeric material. In this article, the atomic oxygen erosion resistance tests of an epoxy-based shape memory polymer are carried out in a ground-based atomic oxygen simulator with a vacuum space chamber. The samples, before and after the atomic oxygen exposure, are compared in appearance, surface morphology, mass, main component, dynamical and static mechanical properties, and shape memory properties. The atomic oxygen exposure causes oxidization reaction of the material, which leads to surface roughen and mass loss, while the shape memory polymer main components remain same. The results of dynamical and static mechanical tests indicate that the atomic oxygen exposure has little effect on the storage modulus and glassy transition temperature (Tg), whereas the elongation, elastic modulus, tensile strength, and yield strength decrease since the atomic oxygen exposure gives rise to tiny cracks. The shape memory property has rarely changed since the atomic oxygen erosion is mainly located near the surface of the sample.

Atomic oxygen resistance of polyimide fibers with phosphorus-containing side chains

Polyimide fibers containing phosphorus showed a denser surface, lower mass loss and less reduction of mechanical properties after atomic oxygen exposure.