(176c) Electrospun Polylactic Acid Filter Media for Filtering Facepiece Respirator Applications

Respiratory personal protection equipment (PPE), such as filtering facepiece respirators (FFRs), reduces disease transmission and exposure to other harmful contaminants through the capture of small aerosolized particles. The N95 respirator has become a widely accepted standard for respiratory PPE for use by the public and healthcare workers. Typically, N95s utilize meltblown polypropylene filter media that is electrostatically charged in order to exhibit sufficient filtration efficiency while maintaining breathability. Reliance on electrostatic charging results in limited shelf and use life, capital-intensive manufacturing, and few decontamination options, all of which contributed to supply shortages during the COVID-19 pandemic. Furthermore, polypropylene is not biodegradable, so widespread use of disposable polypropylene FFRs comes with significant environmental impact.

To address these limitations, electrospinning offers a promising alternative for producing high-performance filter media. Electrospinning is a scalable and adaptable process for manufacturing nonwoven media comprising fibers with diameters less than one micron. It has been demonstrated for a wide variety of materials and used for biomedical scaffolds, catalysis, consumer textiles, and filtration. Previous work has demonstrated that electrospun fibers, being an order of magnitude smaller than meltblown fibers, can achieve N95 filtration performance without the assistance of electrostatic charging. Additionally, nanofibers may degrade more readily than bulk materials due to their high specific surface area. To leverage these advantages to create viable FFRs, additional data on the manufacture and design of these media and their resulting filtration performance is needed.

Here, we describe the development of electrospun polylactic acid (PLA) filter media for FFR applications. PLA is a commercially available biodegradable, bio-based polyester derived from renewable sources. It has been used in applications such as 3D printing, packaging, and textiles. Importantly, PLA is available with differing amounts of D-lactide content, which affects its crystallinity. This, in turn, influences the polymer’s mechanical and thermal properties, as well as its degradation rate. We present structure-property relationships for electrospun filter media from PLA grades with differing D-lactide content that relate their fiber diameter, solidity, and basis weight to air resistance and the filtration of particles 0.01-1 μm in diameter at face velocities relevant for FFR applications. Moreover, we present material designs that balance filtration efficiency and air resistance to meet N95 performance standards. We also explore how these design choices impact degradability.