The Ulm University of Applied Sciences Tests Filter Materials in the Fight Against Covid-19 Using Testing Technology from ZwickRoell

In the course of the Covid-19 pandemic, the need for respirator masks has increased significantly. The Ulm University of Applied Sciences has—initiated by the Biomechatronics Research Group—assembled an interdisciplinary team to develop a concept for particle-filtering respirator masks to the FFP level. In addition to filter performance, air permeability and toxicological safety, important requirements of the materials used include the stability of the fabrics.

Testing for the determination of the strength, stiffness and elongation behavior of selected filter materials was performed according to DIN EN 29073-3, using a ZwickRoell testing machine type Z005. First, strip specimens of flat filter material with a width of 50 mm were extracted in longitudinal and transverse direction and gripped in the testing machine. The maximum force FH and the maximum elongation εH were determined at a constant test speed of 100 mm/min. In addition, the elastic stiffness S of the materials was calculated by linear regression over the initial elongation.

In the first few weeks of the pandemic, the necessary supply of respirator masks and face masks was not available, and in many places DIY masks were being handcrafted or sewn using typical household filter materials such as coffee filters or vacuum cleaner bags. Therefore, the initial focus of the project was on the evaluation of the suitability of those types of materials. Ultimately, the results of the tests carried over to the development of a respirator mask made of high-quality filter materials, in cooperation with an industry partner. The design of the masks is simple and can, among other things, be easily adapted to the facial anatomy of children.

Tensile force-elongation diagram of a non-woven material (example) & definition of the characteristic values
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