The chosen materials are tested on a thermoforming machine KD 20/25, Paul Kiefel Thermoform GmbH,
Freilassing (Germany), where the pressed and preliminary cross-linked sheets are formed by compressed air. The
negative mould is oil-tempered to 180 °C. The mold base is movable. Thus, the forming depth can be varied
between 20 mm and 100 mm.