ABSTRACT
I. INTRODUCTION TO GAS SEPARATION In 1831, Mitchell [1] reported for the first time that gases permeated through rubber membranes and that the flux of each gas was different. At that time, very few polymer membranes had high gas permeabilities and excellent sepa ration properties. In the early 1950s research concerning the separation of he lium from natural gas or for oxygen enrichment from air was begun. As the technology for synthesis of polymers has progressed, many new materials for practical gas separations have been developed. The permeabilities of some polymers to gases are listed in Table 1. Membranes that have both high solu bility and high diffusivity of gases as well as easy membrane formation proper ties are now being used.
