STFI investigates textile applications for PU potting compounds
Saxon Textile Research Institute e.V. (STFI)
Potting compounds made of polyurethane (PU) are traditionally used as a protective and insulating material in electronics and electrical engineering, e.g. in battery modules or on circuits or for embedding LEDs. In addition to their electrically insulating properties, they are heat-resistant and mechanically flexible. Furthermore, the transition from the liquid to the solid aggregate state is so favorable that these PU compounds can be applied precisely. The Sächsisches Textilforschungsinstitut e.V. (STFI) is currently developing two applications on textiles. Firstly, the PU casting compounds are being investigated as a cover layer for sensors that are used to monitor mechanical stress.
The second approach is dedicated to 3D printing on pre-stressed textiles in order to subsequently produce three-dimensionally deformed structures. The current research project “Texsafe” (Reg. No. 49MF220096) focuses on the development of large-area textile sandwich-structured surface elements for monitoring mechanical loads. Suitable coating materials should permanently record the permittivity in order to detect changing mechanical parameters through elastic deformation. In addition, these materials must be able to withstand high loads of up to 1000 kg non-destructively and protect the textile against mechanical damage. In the course of the tests, polyurethane-based casting compounds from WEVO-CHEMIE GmbH, Ostfildern-Kemnat, Germany, proved to be particularly suitable
as they have viscoplastic properties and a high elongation at break. The products in the Wevopur series meet these requirements and have already been successfully tested in extensive test series. The first small-scale functional samples were produced as part of the project, enabling the detection of mechanical loads (Figure 1). The potting compound proved to be particularly suitable here due to its low mixing viscosity, as the textile was well wetted or saturated. The next step will be to scale up to large-area textile sandwich-structured surface elements. The textiles finished in this way can be used in particular in truck loading space detection, for parking lot and floor sensors for access control or surveillance areas. 3D printing on textiles has already been the subject of successful developments at STFI for several years. In this context, new materials for the various 3D application processes are being tested. Selected Wevopur products were also tested as part of the research project “Machine and process development for 3D printing on pre-stretched textiles” (Reg. No. KK5081706WO1).
The application for this special 3D printing requires printing materials that have high flexural strength and SHORE hardness in the upper Shore D range in order to selectively reinforce prestressed textiles using 3D printing. In the test, stretchable PES knitted fabrics were stretched homogeneously and without distortion in the longitudinal and transverse directions using a newly developed tensioning system with defined forces. The textiles were then printed with different geometries using 3D printing. In addition to the classic FDM process, in which thermoplastic filaments are used, the LDM process was also tested. In this process, pasty materials or liquids are processed. Products from the Wevopur series also proved desirable here. The materials were applied to the pre-stretched textiles using a 2-component print head and thus reinforced them selectively. After the printed textile was relieved of pressure, defined deformations occurred. This is also referred to as 4D printing. This technology can be used, for example, to produce individual textile lampshades or acoustic panels (Figure 2) and opens up further application possibilities in architecture. In the project, a good and durable bond with the textile was ensured, which is due to the customized viscosity and good adhesion of the Wevo materials (e.g. WEVOPUR 71/25 MT/3 with WEVONAT 300).
As a result, the successful tests of polyurethane-based potting compounds in combination with textiles at the STFI show new application potential for the Wevopur product series from WEVO-CHEMIE GmbH.
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