Multi-Method Characterization of Compression Set in Fluorosilicone O-Rings

Fluorosilicone o-rings with varying levels of compression set were investigated with a variety of methods. Low field NMR experiments were able to elucidate if the sample had taken a compression set; however, this technique did not have the sensitivity to quantify the relative level of compression set of the o-ring. Water sorption isotherms probe the interior void structure through void space occupation and while complex, the sorption isotherms indicate a systematic loss of void volume with increasing compression set. Similarly, variable temperature 129Xe NMR experiments indicate an elimination of macroscopic void space with increasing compression. The NMR techniques, being noninvasive, have a unique ability to assess the service status of an o-ring in real time.