Scientists from the Fraunhofer Institute for Structural Durability and System Reliability and the Bundesanstalt für Materialforschung und prüfung (BAM) say that they have researched a way to develop flame retardant thermoplastic polyurethane (TPU) more quickly.
According to the institute, the market for TPU s is valued at €1.5 billion, with experts expecting an annual growth of 5.3% until 2025. Besides its qualities such as damping capacity, low-temperature flexibility, chemical stability and wear and abrasion resistance, these types of polymers also display thermal instability and light flammability, which makes the development of flame-retardant materials particularly demanding, Fraunhofer says. Moreover, during the processing of TPU that a high shearing sensitivity can result in a build-up of shear stress, which complicates a uniform dispersion of the flame retardant.
The researchers developed flame-retardant compounds with different formulations for three TPU base materials with different Shore hardness, with the aim of determining the material properties required. Flame retardants were added so that the influence on mechanical parameters would be changed as little as possible. The rapid mass calorimeter was tested as a rapid method of fire behaviour analysis and all results were compared with the corresponding measurements in the cone calorimeter. The accompanying investigation involved pyrolysis using thermoanalytical methods, such as thermogravimetric analysis coupled with the Fourier-transform infrared spectrometer, pyrolysis gas analysis and pyrolysis gas chromatography with mass spectrometry coupling. According to Fraunhofer, it was shown that the rapid mass calorimeter is suitable to evaluate the achieved flame retardance of any flame-retardant TPU. The different TPU types displayed only few, albeit significant differences, e.g. in the mass loss of the individual decomposition stages of pyrolysis and in the mechanics. Some formulations with nitrogen-based flame retardants showed mechanics in the pure material area. However, some proved to be surprisingly similar in terms of fire behaviour and flame retardancy.
This story uses material from Fraunhofer, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
