Durable and impact-resistant thermoset polymers for the extreme environment of low Earth orbit

Abstract

Polymers degrade rapidly in low-Earth orbit (LEO) due to extreme thermal cycling, solar radiation, micrometeoroid and orbital micro-debris impact, and the synergistic erosive effects of atomic oxygen (AO) with UV radiation. In this work, we investigate the synergistic effect of (AO+UV)-induced erosion and high-velocity impact damage on a tough thermoset, polydicyclopentadiene (pDCPD), via erosion yield measurements after a long-term LEO exposure in the ram orientation aboard the International Space Station (ISS) followed by ground-based hypervelocity impact tests. The incorporation of SiO2 nanoparticles reduces the AO-erosion rate by an order of magnitude, while also mitigating the associated degradation of surface mechanical properties. Moreover, the resistance of pDCPD to AO-erosion increases with crosslink density. Hypervelocity impact tests using sub-millimeter laser-driven flyer plates launched at 4.5 km s−1 reveal that pDCPD has higher impact resistance than epoxies with comparable erosion resistance. Interestingly, both epoxy and pDCPD exhibit a statistically insignificant change in impact resistance following surface AO-erosion during direct exposure to space vehicle ram conditions (7.8 km s−1) in LEO.