Temperature-dependent gas transport and its correlation with kinetic diameter in polymer nanocomposite membrane

Abstract

Activation energies for permeation of polymer nanocomposite membrane have not been reported so far. A trade-off relation between permeability and selectivity shows that as permeability increases, the selectivity decreases. Attempts have been made to see this trade-off relation at relatively higher temperature. It is found that selectivity decreases drastically with increasing temperature. A polymer–matrix composite was prepared by adding silica nanoparticles using casting method. Pure gas permeability was measured using a constant volume–variable pressure method at different temperature ranges from 35 to $70^{\circ }\hbox {C}$. The Van’t Hoff relation was used to estimate the activation energy for permeation. It is found to decrease as compared with virgin polycarbonate and it increases with kinetic diameter. For the first time, the permeability and selectivity for nanocomposite membrane are reported as a function of temperature. Activation energies for different gases have been calculated for nanocomposite membrane and compared with that of virgin polymer membrane. Decrease in activation energies for permeation ($E_\mathrm{p}$) with increasing kinetic diameter has been observed for both the membranes. Selectivity reduces with temperature for both the membranes. Mechanical and thermal properties of nanocomposite membrane have been investigated using a dynamic mechanical analyser and differential scanning calorimetry, respectively. Scanning electron microscopy has been used to study surface morphology. The results show modification in physical properties due to incorporation of silica nanoparticles.