Large-scale blow spinning of heat-resistant nanofibrous air filters

Abstract

Particulate matter (PM) pollution has become a serious problem worldwide and various kinds of nanofibrous filters aiming to solve the problem have been developed. It is urgent to remove PM from high-temperature pollution sources, such as industrial emissions, coal furnaces, and automobile exhaust gases. However, filtration at pollution sources remains challenging because most existing air filters are not resistant to high temperature. Herein, heat-resistant polyimide (PI) nanofibrous air filters are fabricated via a simple and scalable solution blow-spinning method. These air filters show excellent thermal stability at high temperature up to 420 °C. They exhibit a filtration efficiency as high as 99.73% at ambient temperature and over 97% at 300 °C. In addition, a field test shows that the filters remove > 97% of PM from the car exhaust fumes. Hence, the blow-spun PI nanofibrous membranes combined with the facile preparation strategy have great potential in high temperature air filtration fields and other similar applications such as water purification and protein separation.

Review on Polymeric, Inorganic, and Composite Materials for Air Filters: From Processing to Properties

“…[67] Thermal imidization of the precursor structure into PI yielded an increase in tensile strength from 2.9 to 8.8 MPa. [104] The incorporation of 4 wt% silica NPs into PVA-PAA fibers could increase the tensile strength from 5.2 to 6.4 MPa. [37] CNTs could improve the tensile strength of hybrid filters by 45% in comparison with pure PI nanofiber membranes, yielding up to 9 MPa.…”

“…[101][102][103] Recently, a multineedle blow spinning device was presented, which allows for large-scale production of PI air filters. [104] Thereby, polyamic acid was used as a precursor and transferred into PI nanofibrous membranes by thermal imidization. Other than that, ceramic yttria-stabilized zirconia (YSZ) nanofiber sponges were produced by blow spinning of a polymeric precursor solution containing zirconium n-propoxide and yttrium nitrate hexahydrate into a porous cage and subsequent calcination, as shown in Figure 6.…”

“…[222] This allows polymers such as PI to be thermally regenerated. [104] Usually, even higher temperatures of more than 500 C are applied to remove adsorbed PM by calcination of inorganic air filters, such as Ag@SiO 2 -TiO 2 or Pt/Al 2 O 3, over several cycles without visible efficiency attenuation. [81,82] Inactivation of SARS-CoV-2 could already be achieved at 85 C on commercial N95 respirators.…”

Face Masks in the New COVID-19 Normal: Materials, Testing, and Perspectives

“…Inspired by Lui's promising results, a variety of electrospun nanofibre membranes with different surface chemistry and mechanical or thermal properties have been developed from polymers, polymer blends, or polymer composites with surface-functionalized inorganic nanofillers for air purification investigations, including polyurethane [127], polycarbonate [128], poly(vinyl alcohol) [129], polytetrafluoroethylene [130], polybenzimidazole [131], polyacrylonitrile/polysulfone [132], polypropylene/polyethylene [133], polyurethane/polysulfonamide [134], polyacrylonitrile/graphene oxide [135], and polyacrylonitrile/MXene [136]. Besides conventional electrospinning, polymer nanofibre membranes mass-produced by needless electrospinning [137] and solution blow spinning [138] also demonstrated effectiveness for the capture of particulate pollutants. To further improve capture efficiency towards ultrafine particles and reduce weight and packing density of the filters to ensure low resistance to airflow, polymer membranes with a novel nanofibre/net hierarchical porous structure have recently been developed using the cutting-edge electrospinning/netting technology, which is a versatile one-step process for fabrication of polymer membranes comprising common electrospun nanofibres interconnected with twodimensional nanonets [143].…”

“…Inspired by Lui's promising results, a variety of electrospun nanofibre membranes with different surface chemistry and mechanical or thermal properties have been developed from polymers, polymer blends, or polymer composites with surface-functionalized inorganic nanofillers for air purification investigations, including polyurethane [ 127 ], polycarbonate [ 128 ], poly(vinyl alcohol) [ 129 ], polytetrafluoroethylene [ 130 ], polybenzimidazole [ 131 ], polyacrylonitrile/polysulfone [ 132 ], polypropylene/polyethylene [ 133 ], polyurethane/polysulfonamide [ 134 ], polyacrylonitrile/graphene oxide [ 135 ], and polyacrylonitrile/MXene [ 136 ]. Besides conventional electrospinning, polymer nanofibre membranes mass-produced by needless electrospinning [ 137 ] and solution blow spinning [ 138 ] also demonstrated effectiveness for the capture of particulate pollutants.…”