Crimped islands-in-the-sea microfibers for highly porous filter textile applications

The development of efficient fiber-based air filter media with increased dust storage capacity and reduced pressure gradient is a key to the advancement of filtration systems in residential ventilation. However, the manufacturing of homogeneous deep-air filter media remains challenging due to the complexity of fiber formation and the predominantly unregulated deposition of fibers in nonwoven structures. This study aims to address these challenges by utilizing continuous crimped islands-in-the-sea fibers for highly porous and efficient filter textile applications, which can be integrated into ventilation system components such as heat exchangers. To define the required filter parameters for the production of highly porous and efficient filter textiles, a mathematical model to simulate the filter characteristics of separation efficiency and pressure drop was derived based on relevant filter theories and evaluated using computational fluid dynamics simulations combined with discrete element method and current literature. The microfibers, essential for the project’s objectives, were produced using the islands-in-the-sea melt spinning technique for polyamide 12, incorporating a water-soluble polyvinyl alcohol as the sea component. The resulting microfibers had diameters of 803 ± 83 nm and exhibited a technical strength of 61.25 ± 1.83 cN/tex. The microfibers were subsequently crimped by two texturing processes: bulked continuous filament and false twist texturing. The force–elongation curves of the textured yarns were analyzed to assess the fiber crimp structure and its suitability for air filtration media. The mathematical model describing fiber crimp and curvature was validated by using scanning electron microscopy. The findings indicate that the ratio of the single islands-in-the-sea fiber bending radius to the microfiber diameter is a critical parameter for producing highly porous structures. It was observed that the false twist texturing process resulted in a threefold crimping contraction of 32.4 ± 4.0%, in comparison with the bulked continuous filament process. Furthermore, it is necessary to analyze both crimp contraction and fiber curvature in order to evaluate the potential of crimped yarns in the development of highly porous and efficient filter textiles. The proposed approach offers promising applications in air filtration, enhancing system efficiency and longevity.