Extended Chemical CrossLinking of a Thermoplastic Polyimide: Macroscopic and Microscopic Property Development
✍ Scribed by Christopher M. Aberg; Ali E. Ozcam; Jacob M. Majikes; Mohamed A. Seyam; Richard J. Spontak
- Book ID
- 102498618
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 288 KB
- Volume
- 29
- Category
- Article
- ISSN
- 1022-1336
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✦ Synopsis
Abstract
Polyimides are well established as gas separation membranes due to their intrinsically low free volume and correspondingly high H~2~ selectivity relative to other gases such as CO~2~. Prior studies have established that H~2~/CO~2~ selectivity can be improved by crosslinking polyimides with diamines differing in spacer length. In this work, we follow the evolution of macroscopic and microscopic properties of a commercial polyimide over long crosslinking times (t~x~) with 1,3‐diaminopropane. According to spectroscopic analysis, the crosslinking reaction saturates after ≈24 h, whereas tensile, nanoindentation and stress relaxation tests reveal that the material stiffens, and possesses a long relaxation time that increases with increasing t~x~. Although differential scanning calorimetry shows that the glass transition temperature decreases systematically with increasing t~x~, permeation studies indicate that the permeabilities of H~2~ and CO~2~ decrease, while the H~2~/CO~2~ selectivity increases markedly, with increasing t~x~. At long t~x~, the polyimide becomes impermeable to CO~2~, suggesting that it could be used as a barrier material.
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