The nonwovens used for FFP-2 masks must filter at least 94 % of aerosols, particles or viruses according to DIN (Source: Freudenberg Performance Materials)
Producing infection control clothing requires a lot of energy and uses lots of material resources. The nonwovens in a mask must filter out at least 94% of the aerosols in the FFP-2 mask according to DIN, and as much as 99% in the FFP-3 variant. At the same time, the mask must let enough air through to ensure that the wearer can still breathe properly. Many manufacturers are looking for ways to optimize the manufacturing process. Furthermore, production needs to be made more flexible so that companies are able to process and deliver versatile nonwovens for a wide range of different applications and sectors.
Researchers at the Fraunhofer Institute for Industrial Mathematics ITWM, Kaiserslautern/Germany, have now developed ProQuIV, a technology that helps save material and energy in the production of nonwovens. All relevant parameters are linked with an image analysis and a digital twin of the production is formed. With its help, nonwoven production can be monitored in real time, automatically controlled and thus the optimization potential exploited. In addition to improving masking production, the ProQuIV solution is also suitable for optimizing production parameters for other applications of the versatile nonwovens.
A method was developed to measure a cloudiness index based on image data. The light areas have a low fiber volume ratio, which means that they are less dense and have a lower filtration rate. Darker areas have a higher fiber volume and therefore a higher filtration rate. On the other hand, the higher air flow resistance in these areas means that they filter a smaller proportion of the air that is breathed in. A larger proportion of the air flows through the more open areas which have a less effective filtration effect.
The transmitted light images from the microscope are used to calibrate the models prior to deployment. The experts analyze the current condition of the nonwovens and use this information to draw conclusions about how to optimize the system - for example, by increasing the temperature, reducing the belt speed or adjusting the strength of the air flows.
The next step for the Fraunhofer team is to reduce the breathing resistance of the nonwovens for the wearer without impairing the protective effect. This is made possible by electrically charging the fibers and employing a principle similar to that of a feather duster. The electric charge causes the textile fabric to attract the tiniest of particles which could otherwise slip through the pores. For this purpose, the strength of the electrostatic charge is integrated into the modeling as a parameter. The Fraunhofer researchers’ plans for the application of this method extend beyond masks and air filters. Their technology is generally applicable to the production of nonwovens - for example, it can also be used in materials for the filtration of liquids. Furthermore, ProQuIV methods can be used to optimize the manufacture of nonwovens used in sound-insulating applications.