Tensile stress effect on the macromolecular orientation and erosion mechanism of an atomic oxygen irradiated polyimide

Polyimides (PIs), used in satellites, are exposed to atomic oxygen (AO) irradiation and subjected to hypervelocity debris impacts which form residual tensile stresses and accelerated erosion.The objectives of this work are to study the PI's macromolecular structure and its deformation and erosion mechanisms when subjected to tensile stresses in an AO environment.The study shows that commercial PI is anisotropic, characterized by two main axis which are related to its semicrystalline structure. Under combined effects of stress and AO irradiation the PI's morphology was dependent on the direction of the applied stress and its magnitude. When the stress was applied parallel to the first main axis a carpet-like texture was formed. When the stress was however applied parallel to the second main axis an ordered surface was formed orthogonal to the direction of the applied stress.A mechanism which relates these findings to the PI macromolecular orientation is suggested.