3D Printing-Aided Fabrication of Recyclable Polyolefin Aerogel Filter Media for Airborne Particle Filtration

Mechanically recyclable thermoplastic polymers are used in preparation of lightweight, high-efficiency aerogel filter media for air filtration with the aid of fused filament fabrication three-dimensional (3D)-printing technique. The all-polyolefin composite filter media is composed of isotactic polypropylene (iPP) gyroid frameworks and high-density polyethylene (HDPE) aerogel infill. The solid content of HDPE needed to obtain a free-standing gel from its solutions is first determined. The aerogel morphology is investigated using scanning electron microscopy and Brunauer-Emmett-Teller nitrogen adsorption analysis. The HDPE aerogel is constructed of lamellar crystalline platelets. The compression tests show that the use of 3D-printed iPP frames in the composite filter media provides adequate compressive modulus (∼100 MPa). The nanometer size pores and the tortuous air flow path are responsible for high filtration efficiency (>99.97%) for the all-polyolefin composite filter media, higher than the standard for high-efficiency particulate absorption filters, typically 99.95%. The study is extended to repurpose 3D-printed filaments obtained from the blends of iPP and HDPE with up to 30 wt % HDPE into fabrication of mechanically strong supporting frames that can host HDPE aerogel. The excellent printability and low warpage values demonstrate the feasibility of repurposing waste polyolefin materials into value-added filter media products.