Polypropylene now recommended for COVID-19 mask filters: What it is, where to get it
Mike EdwardsFeatures COVID-19 The Conversation
Adding a third layer to cloth face masks is now recommended for preventing the spread of COVID-19. Non-woven polypropylene fabric is the material of choice for this third layer, but many people may not know what this material is, or where to get it.
With masks being made at home and by local clothing companies, here’s what you need to know about Public Health Agency of Canada’s new recommendations.
Every study that has examined layering has found that using additional layers in face masks improves filtration, but some fabrics provide more filtration than others. We support the public health recommendation, and specifically recommend the use of industry-grade “spunbond” polypropylene as a middle layer in washable cloth masks.
Spunbond polypropylene destined for the clothing and furniture industries has a fabric-like feel. It is washable and will not divert supply of medical-grade polypropylene from the manufacture of formal personal protective equipment.
The research group the McMaster University Centre of Excellence in Protective Equipment and Materials, with expertise in epidemiology, chemistry, textiles and the mask industry, seeks to improve cloth masks for community use.
Types of non-woven polypropylene
Traditional materials for clothing and furniture have a woven or knitted structure. Non-woven materials, by contrast, have a random arrangement of fibres, like spaghetti on a plate. This randomness enables high particle filtration while remaining highly breathable.
There are many types of non-woven polypropylene. The most common are spunbond, meltblown and spunlace materials.
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