Enhanced resistance to the atomic oxygen exposure of POSS/polyimide composite fibers with surface enrichment through wet spinning

Abstract

We report a series of PI composite fibers containing polyhedral oligomeric silsesquioxane (POSS). These fibers were fabricated by a three-step process consisting of the in situ polycondensation of POSS and polyamic acid, wet spinning, and thermal imidization. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy proved that POSS enriched the surface of POSS/PI composite fibers during wet spinning. This surface enrichment enhanced the resistance to atomic oxygen (AO) erosion. After exposing the POSS/PI composite fibers to AO fluence up to 2.93 × 1020 atoms cm−2, the fibers still displayed excellent AO resistance. With increased POSS content from 0 wt% to 20 wt%, the retention of fracture strength and initial modulus considerably improved from 54% to 93% and from 64% to 91%, respectively. Moreover, the decay rates of fracture strength of the composite fibers obviously decreased at the same AO fluence with increased POSS content from 0 wt% to 20 wt%. AO erosion at a larger fluence further resulted in more effective AO resistance for composite fibers with higher POSS content. XPS results suggested as well that silicate passivated layers formed on the fiber surfaces after AO exposure, and these layers prevented the fibers from further AO erosion.