EFFECT OF LOW-EARTH-ORBIT ATOMIC OXYGEN EXPOSURE ON EPOXY FUNCTIONALIZED SILOXANES

Epoxy functionalized siloxanes (EFS) are a novel class of UV curable m onomers that can be rapidly photopolymerized to give transparent coati ngs and composites. Thin films of these materials have been subjected to low Earth orbit exposure to atomic oxygen (AO) aboard the space shu ttle. It was found that UV cured samples of all four different EFS mon omers exhibited excellent AO resistance both to ambient in-flight cond itions as well as exposure at 120 degrees C. Based on SEM, STM, XPS, a nd weight loss data, it was proposed that AO exposure of these materia ls efficiently produces a thin layer of SiOx at the surface of the sam ple. This layer provides a barrier toward further attack by AO. (C) 19 95 John Wiley and Sons, Inc.