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The Chinese academy of composite materials for ptfe nanometer membrane masks proposed a new direction of protection
At present,face masks have become a necessary item for human hands. With the increase of COVID-19 infection cases, surgical masks products purchased by the whole people from retail channels such as pharmacies have been sold out. On COVID-19 e-commerce platforms, including some KN95 series masks in the flagship store of 3M brand, the masks featured in anti-haze, anti-dust and anti-virus are mostly out of stock and off the shelves.
At present, China's medical masks are mainly divided into three types: surgical masks commonly used in invasive operating environments such as operating rooms with the highest level of protection and disposable medical masks at ordinary levels
The masks that can protect against viruses mainly include surgical masks and N95 masks, and the main material that can filter the viruses in these two masks is the very fine and electrostatic inner filter cloth, which is sprayed by melting and non-woven cloth
Surgical masks are typically made of three layers of nonwoven fabric. The material is spunbonded non-woven fabric + melt spraying non-woven fabric + spunbonded non-woven fabric. The skin touch can also be improved by using staple fiber in the first layer, that is, ES hot rolled non-woven fabric + melt sprayed non-woven fabric + spunbonded non-woven fabric. The outer layer of the mask has a droplet resistant design, middle layer filter, memory moisture absorption. Melt spraying fabric is generally selected 20 grams of weight.
The N95 cup mask is composed of needled cotton, melt-sprayed cloth, and non-woven cloth. The melt spraying fabric usually weighs 40 grams or more, plus the thickness of needled cotton, so it looks thicker than a flat mask, and its protective effect can reach at least 95%.
The main material of melt-sprayed non-woven fabric is polypropylene, a kind of ultra-fine electrostatic fiber cloth, which can capture dust. The droplet containing pneumonia virus will be adsorbed on the surface of the non-woven fabric by static electricity when it is near the melt spraying.
But electrostatic adsorption masks have a huge disadvantage. Static electricity is not always saturated after it is added. In the production, packaging, delivery and transportation of masks, and then in the hands of consumers, when the masks are opened for use, the static content in the non-woven cloth layer will gradually decrease in each link, and the attenuation of static electricity will inevitably lead to the decrease in the protective efficacy of melt-sprayed non-woven masks.
With the increase of wearing time (such as 1 to 2 hours), due to the wearer's breathing and other human activities, the mask is affected by moisture, its electrostatic adsorption capacity is weakened, and the isolation effect gradually becomes worse. Given the tiny size of the virus, conventional surgical masks do not provide lasting protection. For this reason, masks made of PTFE nanometer film have appeared on the market.
Recently, the Chinese society of composite materials published an article proposing a new direction of epidemic prevention development -- ptfe nanofilm masks. Nanometer mask has become a highly effective medical protective mask due to its high filtration performance.
Similar to ordinary medical masks, ptfe nanofilm masks also contain outer, middle, inner, ear hooks, nose clips and other components. The special feature of ptfe nanofilm masks is that the middle layer is composed of a nanofilm with a smaller aperture (100-200 nm), which is generally made of ptfe material.
The PTFE thin film prepared by unidirectional or bidirectional drawing method has a spiderweb microporous structure on its surface, and has very complex changes in the three-dimensional structure, such as network connection, hole inlaying, hole bending, etc., so it has excellent surface filtration function. Ptfe nanofilm mask made of this material has the characteristics of high barrier efficiency, long service life, light and breathable, which is a new direction of mask development in the future.