Quantification of the resistance against deformation under thermal load of different polymeric foams by a novel measuring approach Open Access

In recent years, many (bead) foams have been developed that are claimed to have an elevated resistance to thermal stress. However, there is no uniform technique established to quantify this property; instead, numerous methods exist that vary in quality and reproducibility. When they are all compared, two drawbacks can be identified: (i) these tests usually apply a temperature ramp, which, due to the thermal inertia of foams, leads to temperature gradients within the sample and thus to less reliable results, and (ii) a commonly applied (fixed, constant) mechanical load impairs the possibility of comparing different foams (e.g., different materials, structures, and/or densities). Therefore, from a technical point of view, we have developed a novel approach by combining a static compression test to determine a (relative) test load for each individual foam, which is then applied in a steady creep test with defined temperature steps. Yet, it is possible to quantify a temperature for resistance to thermal deformation (under compression); we propose to call this temperature "heat stability temperature T_HS". We have applied this test to several foams with different densities and foam structures. For example, we were able to show that EPET exhibits a higher temperature resistance than EPP. Furthermore, the T_HS for foams follows the same trend as the heat deflection temperature HDT, obtained from compact samples.