Effect of H⁺ and N⁺ Irradiation on Structure and Permeability of the Polyimide Matrimid®

Abstract

This paper presents a comparison of the impact of H⁺ and N⁺ ion irradiation on the chemical structure, microstructure, and gas permeation properites of the polyimide, Matrimid®. While irradiation with both ions resulted in evolution of chemical structure with loss of functional groups and crosslink formation, there was greater modification of polyimide structure following N⁺ irradiation at similar total deposited energy. Irradiation with N⁺ resulted in simultaneous large increases in permeance and permselectivity at comparatively low ion fluences or irradiation time. For example, irradiation at 4 × 10¹⁴ N⁺/cm² resulted in a 2.5 fold increase in He permeance with a selectivity of He/CH₄ of 340. Much higher H⁺ fluences were required to achieve similar total deposited energy and combined increases in permeance and permselectivity. The larger modification in chemical structure and gas permeation properties following N⁺ irradiation was attributed to the relatively large energy loss and damage from the nuclear energy relative to electronic energy loss.

Keywords:

• Crosslinking
• ion beam irradiation
• gas separation membrane
• hydrogen
• permeability
• polyimide

ACKNOWLEDGEMENT

The support of the National Science Foundation through the Presidential Faculty Fellows (CTS-955367) and CTS 9975452 in funding this project is acknowledged. In addition the authors would like to thank Dr. Peter Simpson of the University of Western Ontario for providing irradiation of the samples.

Notes

^a unit: µm based on the permeance of O₂ of the Matrimid®-ceramic composite membrane and the permeability of O₂ of the bulk material (3).

^b 1Barrer = 10⁻¹⁰ cm³ (STP) cm/cm³·s·cmHg; feed pressure: 55 psig.

^c Ratio of pure-gas permeability.

^a unit: µm based on the permeance of O₂ of the Matrimid®-ceramic composite membrane and the permeability of O₂ of the bulk material (3).

^b 1Barrer = 10⁻¹⁰ cm³ (STP) cm/cm³·s·cmHg; feed pressure: 55 psig.

^c Ratio of pure-gas permeability.

^a unit: µm based on the permeance of O₂ of the Matrimid®-ceramic composite membrane and the permeability of O₂ of the bulk material (3).

^b 1Barrer = 10⁻¹⁰ cm³ (STP) cm/cm³·s·cmHg; feed pressure: 55 psig.

^c Ratio of pure-gas permeability.

^a unit: µm based on the permeance of O₂ of the Matrimid®-ceramic composite membrane and the permeability of O₂ of the bulk material (3).