Determination of desorption activation energies for contaminant species

Abstract

The kinetics of molecular transport of contaminant species is highly dependent on the distribution of desorption activation energies. Accurate measurements of these kinetics are essential to improving confidence in molecular transport modeling and setting appropriate beginning of life (BOL) cleanliness requirements. We present results that combine laboratory experiments with computer simulations to determine the distribution of effective activation energies for outgassing species from a urethane paint system and non-volatile residue (NVR) collected from an ISO Class 5 cleanroom contamination monitoring plate. Outgassing from samples of primer overcoated with urethane paint were analyzed with the temperature controlled quartz crystal microbalance thermogravimetric analysis (QTGA) technique during the final stages of vacuum baking; cleanroom NVR was also analyzed via QTGA. A computer model was developed to simulate the QTGA results. Data from the experimental QTGA were compared to the simulated QTGA to obtain a distribution of desorption activation energies for contaminant species. The interior of the Ozone Mapping and Profiler Suite (OMPS) science instrument is primed and painted with polyurethane/epoxy material. The distribution of activation energies derived in this study was incorporated in the molecular transport model of the OMPS science instrument, on the Suomi National Polar-Orbiting Partnership Satellite, yielding results that are consistent with the on-orbit optical performance data.