Study of glassy polymers fractional accessible volume (FAV) by extended method of hydrostatic weighing: Effect of porous structure on liquid transport

Simulation of the onset of flow through a PTMSP-based polymer membrane during nanofiltration of water-methanol mixture

“…MEMBRANE Let us find the characteristics of pore size distribu tion for the PTSMP membrane using the data pub lished in [20,27,28] Let us now calculate experimental values for the Darcy coefficient of the membrane depending on the applied pressure difference and the ethanol concen tration in the mixture, using the experimental data given in Table 2 21) can be used to determine the active porosity of the mem brane, which was estimated at a value that fairly well falls in the range of variation in the free vol ume of the unrelaxed polymer PTMSP [2,17,20,28 ].…”

“…The experimental procedure has been described in more detail in [3,15,16]. Since PTMSP membranes swell in ethanol (up to 60% [5,17]), they were preliminarily held in the test solution for several hours and then installed in the swollen state in a nanofiltration cell. The volume of the test liquid was selected so that no more than 50% of it passed through the membrane during the experiment.…”

“…Poly[1 (trimethylsilyl) 1 propyne] is known to be a highly permeable polymer having a large nonequilib rium fractional free volume (20-33%) [2,17,20]. Therefore, the degree of disequilibrium of PTMSP films is a very important issue to be taken into consid eration when comparing the results of different exper iments.…”

“…The micro scopic contact angle depends on the disjoining pres sure isotherm [30]; i.e., it is completely determined by surface forces acting on the three phase contact line. A contribution to the change in the macroscopic angle is also made by PTMSP membrane swelling in the water-alcohol mixture, which is manifested at an eth anol content of 20% and reaches 60% when the mem brane is immersed in a 96% ethanol solution [17]. Let us introduce the effective contact angle, which is observed at the beginning of the microscopic motion of the spherical meniscus in a cylindrical pore.…”

“…where The value of corresponds to the membrane having pores with a single radius so that the distribution density is described by the Dirac delta function Substituting expression (17) into Eq. (16) and inte grating, we find an explicit expression for the dimen sionless filtration rate (18) Relationship (18) is schematically shown in Fig.…”