Thermal, X-ray diffraction, and kinetic characteristics of filtration films in the study of ethereal substances

This paper presents the results of the evolution of the structure of filtration films of the MFFC-$3$ and PP-$190$ types in the process of purification of ethereal substances. It has been established by thermogravimetry that a decrease in the mass of samples of working films for MFPC-$3$ by $\sim22\%$, and for PP-$190$ by $18\%$, which is a at temperatures of $\sim130$–$265^{\circ}$C, is due to the destruction of the polymer molecules of the drainage layer as a result of transmembrane pressure and diffusion of ethereal substances. For a pure MFFC-$3$ membrane sample, a single thermal effect is recorded at the peak melting temperature $T_{\text{max}} = 247^{\circ}$С, typical for lavsan with melting enthalpy $\Delta H = 40$ kJ/kg, and for the working sample at $T_{\text{max}} = 249^{\circ}$C with $\Delta H = 19$ kJ/kg. For a clean sample of the pre-filter PP-$190$, a single thermal effect is recorded at the peak melting temperature $T_{\text{max}} = 160^{\circ}$C with $\Delta H = 68$ kJ/kg, and for the working sample at $T_{\text{max}} = 157^{\circ}$C with $\Delta H = 67$ kJ/kg. The bulk crystallinity of the MFFC-$3$ and PP-$190$ films of the working samples decreased by $52$ and $33\%$, respectively, in relation to the initial ones, according to the data of differential scanning calorimetry. X-ray diffraction data indicate changes in the microstructure of films of working samples in the intergranular amorphous phase as a result of deformation of lamellar crystallites, while the X-ray degree of crystallinity of the MFPC-$3$ film decreased by $12\%$, and that of PP-$190$ by $9\%$. On the dependence curves of the hydrodynamic permeability of MFFC-$3$ and PP-$190$ filtration films on time at different transmembrane pressures, four characteristic periods are noted, where gel clots are formed on the MFFC-$3$ membrane, which significantly affect the process of baromembrane separation and the PP-$190$ pre-filter becomes clogged.