In the US, where the number of infected by the coronavirus, has exceeded one million, and killed more than 50 thousand, a question of personal Biosafety as relevant as ever. But the economy is and pharmaceuticals in paralysis, so researchers from Argonne national laboratory and University of Chicago decided to study the materials of which ordinary Americans best positioned to make their own masks. Their conclusions are disappointing – one small error can undo all the efforts.
Testing was subjected to the most simple and available materials: cotton, flannel, silk, chiffon, several types of synthetics. The researchers initially assumed that the protection should be not only layered, but also combined. This is justified – for example, the combination of a cotton-silk or cotton-flannel provides 90 % filtration of particles larger than 300 nanometers and 80 % of the particles less than 300 nanometers. Recall that the size of the coronavirus 80-120 nanometers.
Second conclusion: it is necessary to select such materials to one provided the mechanical filtration and the second electrostatic. The first is cotton as it is woven from threads made from yarn and therefore on the micro level they are very “rough” flying particles cling to them. For the application of the electrostatic filter will fit polyester, this fabric is the accumulated charge attracts small particles, ensuring their retention.
The result is a combined two-layer mask, cheap and gives 80 % guarantee of protection. But when it is worn between the cloth and face formed the slightest gap, the whole effectiveness is eroding. Therefore, scientists declare that in the fabric to insert the elastic bands, staples, to make a rigid frame, the mask pressure to the skin and leave bruises, it will be the proof of its effectiveness.
Source — ACS Nano