MCI seminar, 20 January:
Spatial inhomogeneity, interfaces and complex vitrification behaviour of epoxy-based materials by broadband dielectric spectroscopy and hyphenated calorimetry
By Paulina Szymoniak, Hasan Omar, Xintong Qu, Andreas Schönals. Bundesanstalt für Materialforschung und -prüfung (BAM)
Although in the last decades, epoxy-based nanocomposites have been successfully adopted by the marine, automotive and aerospace industries they are still rarely studied on a fundamental level. This work deals with an in-depth comparative investigation of the structure, molecular mobility and vitrification kinetics of three bisphenol A diglycidyl ether (DGEBA)-based materials with different nanofillers: I) taurine-modified layered double hydroxide (T-LDH), II) boehmite (BNPs) and III) halloysite nanotubes (HNTs). Moreover, the effect of different hardeners (diethylene triamine and methyl tetrahydrophtalic acid anhydride) on the unfilled epoxy matrix is addressed as well. The chosen methodology comprises I) small – and wide – angle X-ray scattering (SAXS/WAXS) II) calorimetry in the forms of a) conventional DSC and b) static fast scanning calorimetry (FSC), III) broadband dielectric spectroscopy (BDS), as well as IV) specific heat spectroscopy in the forms of a) temperature modulated DSC, and b) temperature modulated FSC. The combination of these techniques proved an intrinsic spatial heterogeneity of epoxy-based materials, evidenced by two separate segmental relaxation processes. Although, depending on the hardener the response of the systems to calorimetric and dielectric investigations was different, in a broader sense similar conclusions can be extracted on the structural heterogeneity. As expected from the two distinct α-processes, it was shown that, in parallel to the main glass transition, epoxy-based materials can exhibit an additional low temperature vitrification mechanism, which was not discussed in prior studies for an unfilled network former. Furthermore, the interfacial region (so-called rigid amorphous fraction) was qualitatively and quantitatively addressed, in dependence of the employed nanofiller structure.
Time, place & Zoom link
20 January 2021, 15.00 - 16.00
Online via Zoom: https://syddanskuni.zoom.us/j/65276650969
Host: Horst-Günter Rubahn
To protect the environment, we only provide an online version of the abstract. Should you need to print it, you can contact Sabina Petersen to get a pdf version.