2008 journal article

Extended chemical crosslinking of a thermoplastic polyimide: Macroscopic and microscopic property development

MACROMOLECULAR RAPID COMMUNICATIONS, 29(17), 1461–1466.

co-author countries: United States of America 🇺🇸
author keywords: barrier; calorimetry; crosslinking; networks; polyimides
Source: Web Of Science
Added: August 6, 2018

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. magnified image