(755c) Characteristics of Electrospun Nanofiber Mats and Their Aerosol Filtration Performances As Respiratory Personal Protective Equipment

During the COVID-19 pandemic, respiratory personal protective equipment (PPE) has played a crucial role in controlling and minimizing exposure to respiratory droplets that can transmit the SARS-CoV-2 virus. Conventional filter media for PPE have been produced using meltblown processes, wherein polymer microfibers such as polypropylene are spun to nonwoven fabrics by extrusion. Moreover, these meltblown fabrics are followed by electrostatic charging to be capable of filtering out small particles while providing comfortable breathability. However, the meltblown process is a capital-intensive process carried out at high temperatures in dedicated facilities. Also, the important step of electrostatic charging of the fibers is kept as a proprietary process by conventional PPE manufacturers. These factors have resulted in meltblown fabrics becoming the major bottleneck for respiratory PPE production during the COVID-19 crisis. Along with the critical shortage in respiratory PPE due to the overwhelmed supply chain, the need for alternative production approaches and material options for respiratory filter media has been highlighted.

Electrospinning is a process capable of producing sub-micron diameter fibers with control over the morphology and chemical composition. It has found utility in multiple industries, including HEPA filtration, medical textiles, industrial catalysis, and drug delivery. Market forces have already driven this process due to its low start-up costs and scalability; therefore, it is an excellent approach for respiratory PPE production during a pandemic. To leverage this capability during a time of crisis, performance, process, and materials data are necessary so that electrospun fabric manufacturers can meet the specifications for N95 respirators, as well as responding to surge in demand and managing future outbreaks. Currently, there is limited understanding of and knowledge about the performance of electrospun filter media and required characteristics as respiratory PPE.

Here, we study the correlation between characteristics of electrospun filter media and their performance. The relevant characteristics include the type of polymer material, thickness of fabric, fiber diameter, porosity, and pore size distribution. The evaluation of performance is based on filtration efficiency and pressure drop for breathability. Testing protocols that approximate the National Institute for Occupational Safety and Health (NIOSH) standard for N95 masks are followed. The structure-property relationships for efficient filtration of particles down to 0.07-0.1 micron (i.e., the size of the SARS-CoV2 virus) are presented in this study. In contrast to meltblown fabrics, the filtration efficiency of electrospun nanofibers remains stable over time, as they capture the particles primarily through mechanical mechanisms, although induced electrostatics arising from intrinsic polarity in some polymers may also contribute. Among a wide range of achievable electrospun filter media, we identify specific characteristics of electrospun filter media that are suitable for respiratory PPE and meet the requirements for the existing PPE standards, such as NIOSH N95 masks. Finally, the electrospinning recipes are provided for immediate transfer to the production floor in the industry.