The Effect of the Type and Concentration of the Crosslinking Diene on the Gas Transport Properties of Membranes Based on Polyoctylmethylsiloxane

Abstract

The effect of the type and amount of crosslinking reagent on the gas transport properties of polyoctylmethylsiloxane (POMS) membranes is studied for the first time. 1,7-Octadiene (OD), divinyltetramethyldisiloxane (DMDS), and two samples of polydimethylsiloxane (PDMS 500, PDMS 25000 with the molecular weights of 500, 25 000 g/mol, respectively) are used as crosslinking reagents. The permeability, diffusion, and solubility coefficients are measured for n-butane, methane, carbon dioxide, and nitrogen, and the corresponding ideal selectivities of permeability, diffusion, and solubility are calculated. It is shown that the optimal membrane properties of POMS with the use of DMDS as the crosslinking reagent are achieved at a concentration of DMDS of 3%: the maximum values of the permeability coefficient of n-butane (9400 Barrer) and ideal selectivity of permeability of n-butane/methane (26.1). A decrease in both the selectivity of solubility and selectivity of diffusion is observed for the n-butane/methane gas pair in the DMDS, PDMS 500, and PDMS 25000 series of crosslinking reagents with an increase in the fraction of a siloxane crosslinking reagent.