Perspective, J Nanomater Mol Nanotechnol Vol: 9 Issue: 5
Meltblown Nonwovens and Protective Fabrics: Challenges and Opportunities during COVID-19 and Beyond
Gajanan S Bhat*
Department of Textiles, Merchandising and Interiors, University of Georgia, Athens, GA 30602
Received: October 10, 2020 Accepted: October 17, 2020 Published: November 10, 2020
Citation: Bhat GS (2020) Meltblown Nonwovens and Protective Fabrics: Challenges and Opportunities during COVID-19 and Beyond. J Nanomater Mol Nanotechnol 9:5.
As the COVID-19 cases started increasing in the early months of 2020 in the US and around the world, the major news was about the shortage of Personal Protective Equipment (PPE), especially that of N95 masks. N95 masks are understood to have the ability to provide maximum possible protection against pathogens to the wearer since they filter out at least 95% of the hardest to filter particles that are about 300 nanometres size particles in the aerosols. Since the major
mode of transmission was through the virus being present in aerosols, it made perfect sense. Although Coronavirus, like most of the viruses, is in the range of 60 nm-150 nm in size, the droplets that carry these viruses are in the range of 5 microns-10 microns in size, and good quality N95 masks can effectively capture most of the virus and thus provide a high level of desired protection.
Keywords: Aerosols, N95, Personal protective equipment
As the COVID-19 cases started increasing in the early months of 2020 in the US and around the world, the major news was about the shortage of Personal Protective Equipment (PPE), especially that of N95 masks. N95 masks are understood to have the ability to provide maximum possible protection against pathogens to the wearer since they filter out at least 95% of the hardest to filter particles that are about 300 nanometres size particles in the aerosols. Since the major mode of transmission was through the virus being present in aerosols, it made perfect sense. Although Coronavirus, like most of the viruses, is in the range of 60 nm-150 nm in size, the droplets that carry these viruses are in the range of 5 microns-10 microns in size, and good quality N95 masks can effectively capture most of the virus and thus provide a high level of desired protection.
The critical material of construction in N95 or superior quality masks and many other PPEs is the high-efficiency filter media, a meltblown nonwoven fabric. Melt blowing is a one-step process in which highvelocity hot air is used to draw down the molten thermoplastic polymer into fine fibers . It is an integrated process, consisting of a polymer-feeding system, extruder, metering pump, die assembly, web formation, and a collector. Whereas this system is quite similar to melt spinning of fibers, die configuration, and collection systems are designed in a completely different manner. As the molten polymer is extruded through a linear die into converging streams of hot air, the high-velocity hot air attenuates the fibers. The same air stream conveys the fibers onto a collector. As the fibers move to the collector, they are quenched, and entanglement and bonding take place at the fiber-tofiber contact points, thereby forming a cohesive nonwoven web. The fibers, although continuous, are too small to be handled individually, and the formed web is used. The good part is that the fabric formed directly from the polymer in a single step can be used as a filter, as produced without much modification.
Typical meltblown webs have average fiber diameters in the range of a few microns with a wide distribution in diameters. The desired diameter range depends on the application of the webs, and that can be controlled by the combination of resin and the processing conditions used. Because of the type of the polymer used and the process, the fibers are not necessarily strong, but the fabrics have good barrier properties and serve as ideal materials for high-efficiency filter media.
Meltblown webs are extensively used in fine filtration to remove finer particles and bacteria, and as absorbent products for many applications. Lately, there has been increasing interest in meltblown nanofiber nonwovens as well to achieve high filtration efficiency at lower pressure drop . High-efficiency filter media for HVAC, face masks and respirators use meltblown Polypropylene (PP) of certain fiber diameter range that are also electrically charged. These provide superior filtration efficiency with enough permeability so that they are still breathable while providing a high level of protection from fine particles including bacteria and viruses. As the Covid19 cases started increasing, there was need for more PPE, including N95 masks, especially those offering high filtration efficiency. The Covid19 crisis demonstrated that it is essential to have the infrastructure in the US to develop and produce critical protective materials independent of other countries. One of the major bottlenecks for enhancing the production of N95 masks was the lack of supply of enough meltblown charged PP fabrics .
There was a lot of conversation about increasing PPE production and supply in the US during this pandemic. Whereas there were efforts to increase the production of ventilators, switching existing production of composite fabrics machinery to more meltblown fabric production was a low priority because of the increasing cost as well as the continuing demand for composite products. This shortage of supply with the sudden growth in demand leads to an increase in the cost of meltblown nonwovens. Chinese manufacturers continued to cash on this situation and several new manufacturers of meltblown webs came into existence. Normally it takes much longer to start producing highquality nonwovens because they require precise machinery. However, this sudden sprawling of met blown manufacturers in Yangzhong, one city in China was to cash in on the demand and to make quick money, as the companies found out that with an almost 10-fold increase in the price of these fabrics, this was a highly profitable business . Although the government tried to restrict this uncontrolled growth, several of them tried to move the whole operation to other places. No wonder even today more than 75% of the disposable face masks we use come from China. However, the quality of the majority of these masks is not up to that of N95 masks.
The weaknesses in the global supply chain of PPE as demonstrated during the current pandemic are a reminder of the need for innovation around these critical products so that the developed countries will be better prepared for future endemics. Also, meltblown and spunbond PP are not environmentally friendly, and alternate compostable polymers such as Polylactic Acid (PLA), polyhydroxyalkanoate (PHA), and Poly Polybutylene Succinate (PBS) that are biodegradable thermoplastic resins need to be evaluated for future production of safely disposable facemasks and respirators. Such developments can help other disposable protective fabrics such as medical gowns as well. Although most of the thermoplastic polymers can be processed into meltblown nonwovens, the possibility of producing fine fibers depends on resin characteristics, especially their melt rheology and thermal stability. In addition to that, the ability to charge the webs and form long-term durable electrets needs to be investigated. In addition to these, the development of antibacterial/antiviral protective fabrics can be of benefit as it will provide additional protection to the wearers.
Developing alternative materials to the currently used gold standard of charged meltblown fiber media may help solve multiple problems in the long run. Future research needs to be conducted to develop filter media to be used in N95 and surgical masks from sustainable materials.
- Bhat G (2015) Meltblown submicron fibers for filter media and other applications. International Fiber Journal 20-23.
- Han W, X Wang, Bhat GS (2013) Structure and air permeability of melt blown nanofiber webs. J Nanomater Mol Nanotechnol 2: 1-5.