Efficient, Breathable and Biodegradable Filter Media for Face Masks

Preparation of fluffy bimodal conjugated electrospun poly(lactic acid) air filters with low pressure drop

Electrospun nanofiber membranes have been extensively studied as air filters. However, their limited filtration efficiency for submicron inhalable particulate matter (PM), high resistance to filtration, and limited capacity to hold dust have hindered their widespread use. The majority of materials come from petroleum, and the use of organic solvents during the spinning process has a significant negative impact on the environment. In this work, a sustainable method has been proposed for producing filters using poly(lactic acid) (PLA) with a bimodal diameter distribution through conjugated electrospinning. This technique allows for the continuous production of interconnected micro/nano hybrid porous membranes, resulting in reduced resistance and improved dust holding capacity. The filtration efficiency, pressure drop, long-term filtration performance, and actual performance of the conjugated bimodal membrane (CBM) were extensively investigated. The results indicate that the filter has a high capacity for retaining particles, with filtration efficiencies of 99.94% for PM 0.3 and 99.96% for PM 2.5. It also demonstrates a high quality factor (0.078 Pa-1 for PM 0.3 and 0.084 Pa-1 for PM 2.5), long-term stability (a decrease of 2.35% for PM 0.3 and 0.05% for PM 2.5 over a period of 60 days) and outstanding dust holding capacity (9.17 g m-2). The conjugated bimodal membrane (CBM) shows a 22.64% decrease in resistance compared to the non-conjugated bimodal membrane (BM). In general, the approach outlined in this work provides valuable insights into the development of high-performance biodegradable air filters. These filters have improved filtration efficiency and reduced resistance.

Guidelines for measuring and reporting particle removal efficiency in fibrous media

Adopting standardized and reliable methodologies to accurately measure particle removal efficiency when developing fibrous materials for controlling airborne contamination is crucial. Here, the authors recommend best practices for experimental assessments and reporting to ensure a reliable evaluation of new airborne particle filtration media and technologies.

PTFE/PVA-PVDF Conjugated Electrospun Nanofiber Membrane with Triboelectric Effect Used in Face Mask

COVID-19 broke out all over the world, and the medical protective mask is an important epidemic prevention equipment. Traditional medical protective masks use electret polypropylene melt-blown cloth as the core filter material. However, it relies heavily on electrostatic filtration and has high filtration resistance. The one-time electret makes the static charge decay rapidly with the water vapor generated by breathing, which affects the service life of the mask. In this paper, PTFE/PVA fiber and PVDF fiber were fabricated by conjugate electrospinning method, and the PTFE/PVA-PVDF layer blending fluffy fiber membrane was obtained by on-line mixing. Under the action of air slip effect and triboelectric secondary electret, the fiber membrane has higher filtration efficiency, lower filtration resistance and longer service life. The initial filtration efficiency of the fiber membrane is above 95%, the filtration efficiency is near to 100% after 24 times of cyclic filtration, the filtration resistance is about 110 Pa, the air permeability of the fiber membrane is 262.88–370.70 mm/s, and the moisture permeability is as high as 7721–8471 g/ (m2·24 h).