Identification of volatile butyl rubber thermal-oxidative degradation products by cryofocusing gas chromatography/mass spectrometry (cryo-GC/MS).

Chemical structure and physical properties of materials, such as polymers, can be altered as aging progresses, which may result in a material that is ineffective for its envisioned intent. Butyl rubber formulations, starting material, and additives were aged under thermal-oxidative conditions for up to 413 total days at up to 124 °C. Samples included: two formulations developed at Kansas City Plant (KCP) (#6 and #10), one commercially available formulation (#21), Laxness bromobutyl 2030 starting material, and two additives (polyethylene AC-617 and Vanax MBM). The low-molecular weight volatile thermal-oxidative degradation products that collected in the headspace over the samples were preconcentrated, separated, and detected using cryofocusing gas chromatography mass spectrometry (cryo-GC/MS). The majority of identified degradation species were alkanes, alkenes, alcohols, ketones, and aldehydes. Observations for Butyl #10 aged in an oxygen-18 enriched atmosphere ( 18 O2) were used to verify when the source of oxygen in the applicable degradation products was from the gaseous environment rather than the polymeric mixture. For comparison purposes, Butyl #10 was also aged under non-oxidative thermal conditions using an argon atmosphere. UNCLASSIFIED UNLIMITED RELEASE (UUR) UNCLASSIFIED UNLIMITED RELEASE (UUR) 4 ACKNOWLEDGMENTS The authors gratefully acknowledge the contributions of Donald R. Bradley for his assistance in sample preparation and aging. We would also like to thank Mark Wilson for providing the butyl rubber samples as developed by him at Kansas City Plant. Funding was provided by the Enhanced Surveillance Campaign (ESC). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DEAC0494AL85000. UNCLASSIFIED UNLIMITED RELEASE (UUR) UNCLASSIFIED UNLIMITED RELEASE (UUR) 5 CONTENTS