Effect of Treatment of PTMSP Films with Supercritical CO2 and CHF3 on Their Mechanical and Gas Transport Properties

Abstract

The paper investigates the effect of treating poly(1-trimethylsilyl-1-propyne) (PTMSP) films with supercritical CO₂ and CHF₃ on their mechanical properties and gas permeability. Treatment of PTMSP films with supercritical fluids (SCFs) 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 treating films under high pressure (35 MPa). It was shown that the permeability coefficients of films treated at a pressure of 15 MPa either remain as that of the original untreated film (after treatment for 3 h) or decrease significantly (after prolonged treatment for 20 h). At the same time, treatment of the films at a higher pressure of 35 MPa leads to a noticeable increase in the permeability coefficients. The films treated with SCFs have a noticeably slower rate of decrease in permeability coefficients over time in comparison with the untreated films: after 1 year of storage in air, the O₂, N₂, and CO₂ permeability coefficients decreased by 50–60% for the untreated film, while in the treated films the permeability decrease over the same period was 10–40%. The permeability after 1 year for the sample with the greatest increase in permeability after treatment with SCFs was close to the initial permeability of the untreated film. It was demonstrated that, by varying the type of fluid and the film treatment conditions, it is possible to carry out structural modification of PTMSP and effectively influence both the permeability and the preservation of transport parameters over time.