Effects of prior aging at 288°C in air and in argon environments on creep response of PMR-15 neat resin
Document Type
Article
Publication Date
1-5-2009
Abstract
The creep behavior of PMR-15 neat resin, a polyimide thermoset polymer, aged in air and in argon environments at 288°C for up to 1000 h was evaluated. Creep tests were performed at 288°C at creep stress levels of 10 and 20 MPa. Creep periods of at least 25-h in duration were followed by 50-h periods of recovery at zero stress. Prior isothermal aging increased the elastic modulus and significantly decreased the polymer's capacity to accumulate creep strain. The aging environment had little influence on creep and recovery behaviors. However, aging in air dramatically degraded the tensile strength of the material. Dynamic mechanical analysis revealed an increase in the glass transition temperature from ∼330°C to ∼336°C after 1000 h in argon or in air at 288°C. The rise in the glass transition temperature with aging time is attributed to an increase in the crosslink density of the PMR-15 polyimide. Increase in the crosslink density due to aging in both air and argon environments is likely behind the changes in the elastic modulus and the decreased capacity for inelastic straining. A visibly damaged surface layer of ∼0.16 mm thickness was observed in specimens aged in air for 1000 h. Results indicate that the unoxidized core material governs the overall mechanical response, whereas the oxidized surface layer causes a decrease in tensile strength by acting as a crack initiation site and promoting early failures.
Source Publication
Journal of Applied Polymer Science (ISSN 0021-8995)
Recommended Citation
Ruggles-Wrenn, M.B. and Broeckert, J.L. (2009), Effects of prior aging at 288°C in air and in argon environments on creep response of PMR-15 neat resin†‡. J. Appl. Polym. Sci., 111: 228-236. https://doi.org/10.1002/app.28766
Comments
© 2008 Wiley Periodicals
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