Usability of Low-Density Polyethylene Thin-Film for Planetary Protection controlled applications: Strength degradation due to Gamma Irradiation

The material selection for the hull of a sounding balloon as reference application for the use on Mars requires, among other aspects, the consideration of planetary protection. One candidate material, 5 µm low-density polyethylene (LDPE) thin-film, cannot be sterilized through common methods in the space industry like dry heat microbial removal, but for example through gamma irradiation, which is commonly used in the medical sector. In order to quantify the impact of gamma radiation on the strength of LDPE, several samples were sterilized with absorbed doses between 18 and 50 kGy. Afterwards, the bio burden of the samples for each dose were assessed together with their remaining tensile strength. The investigation showed statistically significant changes of strength in the film’s longitudinal and lateral direction due to scission and cross-link effects on the material polymers. With regard to planetary protection, this study showed that an absorbed dose of about 25 kGy is required to reduce the bioburden to be near the detection limit of the assessment.