Key words: polymeric membranes, poly(1-trimethylsilyl-1-propyne), supercritical fluids, gas permeation, mechanical properties
The effect of SC-CO2 and SC-CHF3 treatment of poly(1-trimethylsilyl-1-propyne) [PTMSP] films on their mechanical properties and gas permeability was investigated. Treatment of PTMSP films in supercritical fluids (SCF) leads to a decrease in the elastic modulus (Young’s modulus, E) and an increase in the relative elongation at break (ε), which is especially pronounced when processing films under high pressure (35 MPa). It is shown that the permeability coefficients of films treated at a pressure of 150 MPa either remain at the level of the initial untreated film (time of treatment 3 hours) or decrease noticeably (time of treatment 20 hours). At the same time, treatment of the films at a higher pressure of 35 MPa leads to a noticeable increase in the permeability coefficients. Films treated with both SCFs have a noticeably lower rate of decrease in permeability coefficients over time compared to untreated PTMSP. Thus, in untreated film after 1 year of storage in air, the permeability coefficients for O2, N2 and CO2 decreased by 50—60 %, while in treated films, the decrease in permeability over the same period is 10—40 %. The permeability values after 1 year for the sample with the greatest increase in permeability after treatment in SCF are close to the level of the initial permeability values of the untreated film. Thus, the work shows that by varying the type of fluid and the mode of film treatment, it is possible to carry out structural modification of PTMSP and effectively influence both the level of permeability and stabilization of transport parameters over time.