Phase Separation of Polymethylpentene Solutions for Producing Microfiltration Membranes
Microfiltration membranes have been obtained from polymethylpentene by phase separation of its dioctyl sebacate solutions under cooling. The dissolution of the polymer was carried out at its melting point followed by formation of membrane precursors in the form of films from the resulting solution, which were then cooled and washed with acetone to remove the ester and pore formation. Using laser interferometry, it is shown that the phase diagram of the polymethylpentene–dioctyl sebacate system corresponds to amorphous separation with the UCST. The rheology of solutions is studied by rotational rheometry, and it found that the logarithm of viscosity decreases linearly with increasing concentration of dioctyl sebacate. According to calorimetry, dioctyl sebacate plasticizes polymethylpentene, reducing its crystallinity. Treatment of the resulting films with acetone leads to the complete extraction of dioctyl sebacate, and, at its concentration of 25–45 wt %, a through porous structure is formed. This procedure makes it possible to obtain fairly strong membranes with a water permeability of 16.4 kg/(m2 h atm) and a retention coefficient of submicron particles with a diameter of 240 nm equal to 80%.