Compatibility Testing of Polymeric Materials for the Urine Processor Assembly (UPA) of International Space Station (ISS)

摘要

In the International Space Station (ISS), astronauts will convert urine into potable waterrnwith the UPA by a distillation process. The urine is pre-treated, containing flush water andrnstabilizers. About 2.5% solids in the urine are concentrated up to 16% "brine" throughrndistillation. Dynamic mechanical analysis (DMA) in the stress relaxation mode was primarilyrnused to test 15 polymeric UPA materials for compatibility with the pre-treated and brinernsolutions. There were concerns that chromium trioxide (CrO_3), a stabilizer not in the originalrnpre-treat formulation for similar compatibility testing in 2000, could have an adverse effect onrnthese polymers. DMA testing is partially complete for polymeric material samples immersed inrnthe two solutions at room temperature for as long as 200 days. By comparing each materialrn(conditioned and virgin), the stress relaxation modulus (E) was determined for short-term usernand predicted for as much as a 10-year use in space. Such a ΔE showed a decrease of as much as 70 for a Nylon material,rnbut an increase as much as 454% for a polysulfone material, withrnincreasing immersion time.