Blocking of Gas–Liquid Coalescing Filters with Accumulated Oil during the On–Off Operation of a Filtration System

The study aims to eliminate the effect of coalescing filter blocking due to on–off operation by changing the wetting properties of the non-woven fiberglass filter media through their chemical modification with the use of a polydimethylsiloxane (PDMS) solution in hexane and a few commercial products that give the surface oleophobic properties. The best results—high separation efficiency, no redispersion of droplets at the outlet, and low flow resistance—were obtained for materials coated by immersion in a 0.2% PDMS solution, for which a reduction in oleophilicity was found, but the material was not oleophobic and still moderately wetted with the test liquid. The corresponding static contact angle with the VG-46 rotary compressor oil measured on the flat borosilicate glass wafer made of the same material as the fiberglass media was equal to 54° for the PDMS dip-coated surface. Moreover, the good stability of the applied polymer on the material surface was confirmed by the SEM imaging, the FTIR analysis, and maintaining a high performance in multiple tests run for a single coalescing element.