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Why does Kevlar decompose, while Nomex does not, when treated with aqueous chlorine solutions?
Akin Akdag1, Hasan B Kocer, S D Worley
1Department of Chemistry and Biochemistry and Department of Polymer and Fiber Engineering, Auburn University, Auburn, Alabama 36849.
The Journal of Physical Chemistry. B
|May 1, 2007
Summary
Kevlar decomposes when treated with bleach, unlike Nomex. This study found Kevlar’s diaminophenylene component oxidizes to a quinone, causing decomposition, while Nomex remains stable, explaining their different reactions to chlorination for biocidal applications.
Area of Science:
- Polymer Chemistry
- Materials Science
- Biocidal Applications
Background:
- High-performance polymers Kevlar and Nomex have potential biocidal applications.
- Reaction with sodium hypochlorite solution can create biocidal N-halamine groups.
- Kevlar decomposes during chlorination, while Nomex does not.
Purpose of the Study:
- To investigate the differing stability of Kevlar and Nomex under chlorination conditions.
- To elucidate the chemical mechanisms behind Kevlar's decomposition during N-halamine formation.
Main Methods:
- Synthesis of polymer mimics for Kevlar and Nomex.
- Treatment of mimics with hypochlorous acid (a component of bleach).
- Spectroscopic analysis to identify reaction products and mechanisms.
Main Results:
- The p-diaminophenylene component in the Kevlar mimic was oxidized to a quinone structure.
- This quinone intermediate subsequently decomposed.
- The Nomex mimic did not undergo a similar decomposition pathway.
Conclusions:
- The oxidation and subsequent decomposition of the p-diaminophenylene moiety explain Kevlar's instability.
- This mechanistic difference accounts for why Nomex is stable under chlorination while Kevlar is not.
- Understanding these mechanisms is crucial for developing N-halamine biocidal materials from these polymers.
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