Investigation of the dispersion process of polypropylene glycol in perfluorodecalin

Abstract

Perfluorinated polyesters (PFPE) are used as components of high-performance lubricants and oils operating in high and low temperature conditions, including in special-purpose products used in space and in Arctic conditions. To date, the methods for producing PFPE are complex processes that are quite demanding to the conditions of synthesis, which makes it almost impossible to produce these compounds commercially on a large scale. One of the promising approaches to obtaining perfluorinated esters is liquid-phase direct fluorination. Toxic, ozone-depleting solvents have been used in these processes. When they are replaced with harmless, perfluorinated liquids, for example, perfluorodecalin (PFD), another problem is found – the original polyesters are insoluble in PFD, which is confirmed by laser microinterferometry. In this regard, ultrasonic dispersion of the initial polypropylene glycols (PPGs) of various molecular weights in PFD was proposed in order to obtain emulsions for subsequent direct fluorination. The resulting emulsions were studied using gel-penetrating chromatography, dynamic light scattering and gravimetry. According to the results of the study, the values of particle sizes and emulsion concentrations were obtained over time after ultrasound, and it was also concluded that the stability of the molecular weight of PPG in the emulsion after sonification. The applicability of ultrasonic dispersion for a high specific surface area of the phase boundary in the PPG – PFD system is discussed, and the feasibility of sonification in a continuous or batch mode when implementing liquid-phase fluorination of PPG in PFD is also discussed.