An experimental study on the filtration performance of a poly-alpha-olefin-compatible expanded polytetrafluoroethylene high-efficiency particulate air filter

ABSTRACT Filter media made of expanded polytetrafluoroethylene filters are known to be incompatible with poly-alpha-olefin or any oil-based challenge particles, and thus, filters made of expanded polytetrafluoroethylene had limited use in pharmaceutical applications. The benefits of expanded polytetrafluoroethylene filters, e.g. intrinsic durability, more energy-efficient, chemical inertness, etc., are therefore not being fully utilized. A new expanded polytetrafluoroethylene filter media compatible with poly-alpha-olefin particles was then developed by a filter manufacturer. The goal of this study is to investigate the filtration performance and characteristics of the new expanded polytetrafluoroethylene media and to compare it with the conventional expanded polytetrafluoroethylene media. In this study, four pleated high-efficiency particulate air filters made of either the conventional or the new expanded polytetrafluoroethylene media, and either of the two variants of pleat depths (36 mm and 31 mm) were tested under two different challenge tests, one using potassium chloride (KCl) salt particles and the other using poly-alpha-olefin particles. Both challenge particles are submicron and polydisperse. The collection efficiency, pressure drop, and dust holding capacity were measured in both tests. Due to the sensitivity of KCl particle release to environmental factors, a repeatability test was also performed for the KCl test. poly-alpha-olefin test results show that the new expanded polytetrafluoroethylene filter performed remarkably better than the conventional expanded polytetrafluoroethylene filter, achieving a high amount of dust retention at the same preset final pressure drop.