Primary Polymer Aging Processes Identified from Weapon Headspace Chemicals
A current focus of our weapon headspace sampling work is the interpretation of the volatile chemical signatures that we are collecting. To help validate our interpretation we have been developing a laboratory-based material aging capability to simulate material decomposition chemistries identified. Key to establishing this capability has been the development of an automated approach to process, analyze, and quantify arrays of material combinations as a function of time and temperature. Our initial approach involves monitoring the formation and migration of volatile compounds produced when a material decomposes. This approach is advantageous in that it is nondestructive and provides a direct comparison with our weapon headspace surveillance initiative. Nevertheless, this approach requires us to identify volatile material residue and decomposition byproducts that are not typically monitored and reported in material aging studies. Similar to our weapon monitoring method, our principle laboratory-based method involves static headspace collection by solid phase microextraction (SPME) followed by gas chromatography/mass spectrometry (GC/MS). SPME is a sorbent collection technique that is ideally suited for preconcentration and delivery of trace gas-phase compounds for analysis by GC. When combined with MS, detection limits are routinely in the low- and sub-ppb ranges, even for semivolatile and polar compounds. To automate this process we incorporated a robotic sample processor configured for SPME collection. The completed system will thermally process, sample, and analyze a material sample. Quantification of the instrument response is another process that has been integrated into the system. The current system screens low-milligram quantities of material for the formation or outgas of small compounds as initial indicators of chemical decomposition. This emerging capability offers us a new approach to identify and non-intrusively monitor decomposition mechanisms that are accelerated by stockpile-relevant aging parameters such as heat, irradiation, material incompatibility and physical force. The primary organic material groups that make up many of the weapon systems are chlorofluoropolymers, polysiloxanes, and polyurethanes (PUR). In the weapon headspace we see the greatest residue from polysiloxanes and PUR and, therefore, are interested in identifying and quantifying the origin responsible for their presence. Although we have produced a number of significant findings concerning the chlorofluoropolymer and polysiloxane materials, this work focuses on the decomposition of PUR.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15005694
- Report Number(s):
- UCRL-JC-147870; TRN: US200324%%65
- Resource Relation:
- Conference: 24th Aging, Compatibility and Stockpile Stewardship Conference, Amarillo, TX (US), 04/30/2002--05/02/2002; Other Information: PBD: 25 Mar 2002
- Country of Publication:
- United States
- Language:
- English
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