The biggest challenge when developing filtering face pieces (FFP) is to guarantee the required level of protection while keeping breathing resistance as low as possible. For instance, the FFP2 classification according to the DIN EN 149 standard requires that at an air flow rate of 95 l/min, particle penetration must not exceed 6% and breathing resistance must not exceed 2.4 mbar [1].

The aim of the SULA (“Safer and Easier Breathing”) research project was to significantly reduce both permeability and breathing resistance compared to the FFP2 classification by improving the production and processing of the nonwoven fabric and selecting the optimal (combination of) nonwoven media for the manufacture of the filter mask. Expertise from industry and application-oriented research was pooled to investigate the interaction of the individual process steps and their effects on the final product. The company Reifenhäuser Reicofil was responsible for producing nonwoven fabric samples and conducting experimental investigations into process design for the meltblown and hydrocharging processes.

IMSTec carried out material characterization of the samples and measured their filter performance, produced masks from the nonwoven fabrics, and tested them for compliance with the specifications. The main tasks for Fraunhofer ITWM were to create models and perform simulations for the most important steps in nonwoven fabric production, as well as to optimize the mask material. in such a way that the protection level is higher than required by the FFP2 standard and

For a meltblown nonwoven to meet the specifications, the fibers are electrostatically charged. In this project, the focus was on the hydrocharging technology, which is applied already during fiber production and thus promises an even distribution of the electric charge in the nonwoven. Extensive test runs on the nonwoven fabric line in conjunction with systematic simulation studies led to a significant improvement in the filter efficiency of the nonwoven fabrics without significantly increasing breathing resistance, as subsequent analysis of the filter performance showed.

The data on flow resistance and separation efficiency served as the basis for identifying models to predict filter performance. Linking these models to the manufacturing process made it possible to produce better nonwovens for personal protection. The models could also be used to find optimal combinations of the new nonwoven fabrics so that the final mask would have the desired improved properties.

In this presentation, we will introduce the project and the key aspects of the research and development work carried out and discuss the results. We will also address the insights gained and provide an outlook for the future.