Polymer, Additives, and Processing Effects on N95 Filter Performance.

Area of Science:

• Polymer Science
• Materials Science
• Filtration Technology

Background:

• The COVID-19 pandemic underscored the critical need for N95 respirators.
• Polypropylene (PP) is the standard material for N95 filtration media, but selecting optimal precursors requires extensive testing.
• Shortages of N95 masks necessitate efficient methods for identifying and developing suitable PP materials.

Purpose of the Study:

• To differentiate between commercial grades of polypropylene (PP) for N95 filtration media production.
• To demonstrate the development of effective N95 filtration media from various PP types.
• To aid industry partners in addressing N95 mask shortages by identifying key material properties.

Main Methods:

• Three high melt flow index PP grades were melt blown and characterized.
• Techniques included differential scanning calorimetry (DSC), X-ray diffraction (XRD), and neutron scattering.
• The impact of corona charging and additives on filtration performance was evaluated.

Main Results:

• Despite similar melt flow and isotacticity, PP grades varied significantly in their response to corona charging and additives.
• Polymer crystallization properties were identified as the most critical differentiating factor.
• Higher crystallization onset temperatures, slower crystallization rates, and more crystallites led to stronger electret formation.

Conclusions:

• The crystallization behavior of polypropylene is crucial for effective electret formation in N95 filtration media.
• Materials with specific crystallization characteristics yield superior filtration performance.
• Understanding these properties can streamline the selection of PP for N95 mask production and mitigate shortages.