Polyimide-Organosilicate Hybrid Materials Part I: Effects of Annealing on Gas Transport Properties Part II: Effects of CO2 Plasticization

Type of Document Master's Thesis
Author Hibshman, Christopher L.
URN etd-05082002-142425
Title Polyimide-Organosilicate Hybrid Materials Part I: Effects of Annealing on Gas Transport Properties Part II: Effects of CO2 Plasticization
Degree Master of Science
Department Chemical Engineering
Advisory Committee
Advisor Name Title
Dr. Eva Marand Committee Chair
Dr. Ravi Saraf Committee Member
Dr. Rick Davis Committee Member
Keywords

* Inorganic Membranes
* Composite Membranes
* Gas Separation
* Polyimide
* Organosilicate

Date of Defense 2002-05-03
Availability unrestricted
Abstract

The objective of this study was to examine the effects of annealing polyimide-organosilicate hybrid membranes on gas transport. In addition, the effects of carbon dioxide pressure on the gas transport of unannealed polyimide-organosilicate hybrid membranes were evaluated. The membranes in both studies consisted of sol-gel derived organosilicate domains covalently bonded to a 6FDA-6FpDA-DABA polyimide using partially hydrolyzed tetramethoxysilane (TMOS), methyltrimethoxysilane (MTMOS) or phenyltrimethoxysilane (PTMOS).

The first study subjected the hybrid membranes to a 400°C annealing process to enhance gas separation performance by altering the organosilicate structures. The hybrid membranes were evaluated before and after annealing using pure gases (He, O2, N2, CH4, CO2) at 35°C and a feed pressure of 4 atm. The permeability for most of the membranes increased 200-500% after the annealing process while the permselectivity dropped anywhere from 0 to 50%. The exceptions were the 6FDA-6FpDA-DABA-25 22.5 wt% TMOS and MTMOS hybrid membranes, both of which exhibited increases in the CO2 permeability and CO2-CH4 permselectivity. The increase in permeation was attributed to increases in the free volume and enhanced segmental mobility of the chain ends resulting from the removal of sol-gel condensation and polymer degradation byproducts.

For the second study, the transport properties of four membranes, 6FDA-6FpDA polyimide, 6FDA-6FpDA-DABA polyimide, MTMOS and PTMOS-based hybrid materials, were characterized as a function of feed pressure to evaluate how the hybrid materials reacted to CO2 plasticization. Steady-state gas permeation experiments were performed at 35°C using pure CO2 and CH4 gases at feed pressures ranging from 4 to 30 atm. All four materials exhibited dual mode sorption up to feed pressures of 17 atm, at which point the effects of CO2 plasticization were observed.

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