Thermogravimetric studies of dehydration of the cellulose acetate layer in UAM-100, UAM-150, and MGA-95 composite films

This paper presents an analytical overview of the study of the kinetic and physicochemical characteristics of composite membrane films. UAM-100, UAM-150, and MGA-95 composite films have been studied using thermogravimetry in the temperature range from 30 to 300$^{\circ}$C. A kinetic analysis of experimental data by the Freeman–Carroll method is carried out. It was found that hydrated water for all the studied semi-permeable films evaporates in the temperature range from $\sim$95 to $\sim$180$^{\circ}$C. Comparison of the ratios of the amount of removed water in the film samples correlates with the geometric parameters of the pores. The values of the activation energy and the pre-exponential factor ($E$ = 26.9 kJ/mol and $\ln(A\approx 6.3 (\min^{-1}))$ in the range 0.2 $<\alpha<$ 0.7 of the degree of dehydration indicate the same regularity in the distribution of water molecules in the polymolecular layer for all composite films. The high dehydration values, e.g., for a sample of a composite semipermeable film MGA-95 at the temperature of the maximum on the thermogravimetry curve ($T_{\operatorname{max}}$ = 169.6$^{\circ}$C) indicate that water molecules form hydrogen bonds both with ionogenic groups of cellulose acetate and with each other.