Exposure of cross-linked epoxy resins to the space environment

Two specimens of cross‐linked epoxy resins were attached to the Remote Manipulator Arm (“Canadarm”) of the space shuttle and exposed to the space environment (about 225 km altitude) experienced on the 41‐G shuttle mission. Portions of the specimens which had been coated with 10 nm of inconel, then gold, were relatively unaffected by space exposure, while the uncoated areas were eroded to a depth of about 5 μm. The eroded surfaces had a porous texture, consisting of tunnel‐like features extending a further 10 μm below the surface, with a hole density of 3 × 106 holes/mm2. Surface infrared (IR) spectroscopy showed that the first 1–2 μm of porous surface material was little affected chemically by the erosion process, indicating that any chemical erosion must have occurred progressively in a very thin surface layer, which then volatilized away, exposing fresh surface for attack. As a qualitative laboratory simulation, specimens of the same plastics were exposed to low‐pressure air and oxygen plasmas. Somewhat similar surface damage was observed, with no IR‐detectable change in surface chemistry. The criteria for selection of a satisfactory laboratory simulation of the space environment, and the factors responsible for the directionality of the erosion processes are discussed.