Investigation of the applicability of the time-temperature superposition principle within the cryogenic temperature range, illustrated by a two-component epoxy adhesive

Adhesives tend to become brittle in very cold and cryogenic environments. This has a significant influence on the mechanical behaviour of an adhesive bond. In this study, the two-component epoxy Scotch-Weld 2216 B/A is mechanically characterized as a function of temperature. For this purpose, a dynamic mechanical analysis (DMA) is performed on tensile specimen covering a temperature range from −170°C to 100°C and a frequency range from 0.1 Hz to 10 Hz. Furthermore, the adhesive material is examined for rheological simplicity in order to apply the principle of time-temperature superposition (TTS) both for a reference temperature at room temperature (RT, 20°C) and for the cryogenic temperature range (CT, −150°C). The present article thus conducts a comparative analysis of the divergent approaches to determining the shift factors according to WLF (Williams-Landel-Ferry) and Arrhenius in the α- and γ-transition. The results reveal a successful application of TTS at both temperature regions using the WLF as well as the Arrhenius methods. Both approaches lead to steady and plausible master curves that cover nine (CT) or 18 (RT) decades. In the context of the Arrhenius approach, it was observed that the peaks of the loss modulus are more suitable than those of the loss factor for the determination of the apparent activation energy.