Dielectric relaxation mechanisms in polyoxymethylene/polyurethane/layered silicates hybrid nanocomposites

• Published in: European polymer journal 2017-10, Vol.95, p.304-313
• Main Authors: Tomara, G.N., Karahaliou, P.K., Psarras, G.C., Georga, S.N., Krontiras, C.A., Siengchin, S., Karger-Kocsis, J.
• Format: Article
• Language: English
• Subjects: Broadband; Compounding; Dielectric relaxation; Dielectrics; Direct melting; Electron microscopy; Latex; Morphology; Nanocomposites; Polyurethane; Polyurethane resins; Scanning electron microscopy; Silicates; Spectra; Studies
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2017.07.037

[Display omitted] •POM/PU/LS nanocomposites produced by Direct Melt (DM) compounding.•POM/PU/LS nanocomposites produced by latex-mediated Masterbatch (MB) technique.•Better dispersion of LS is achieved in the case of the MB produced nanocomposites.•Dielectric relaxations of PU (α & γ) are not affected by the preparation technique.•γ- & δ-relaxations of POM appear as two distinct peaks (DM) or as one broad (MB). Polyoxymethylene/Polyurethane/Layered Silicates (POM/PU/LS) ternary hybrid nanocomposites were prepared by two methods: (a) direct melt compounding (DM) and (b) melt compounding using a latex-mediated masterbatch (MB) technique. The morphology of the produced specimens and the quality of the dispersion of LS (synthetic sodium fluorohectorite) were examined via Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Broadband dielectric spectroscopy (BDS) was employed in order to study the dielectric response of the two systems in a wide frequency and temperature range. Rich dielectric spectra are recorded, since dielectric relaxation mechanisms originate from POM matrix, PU latex as well as from interfacial phenomena between electrically heterogeneous components of the nanocomposite. Six different mechanisms contribute to the recorded spectra of the examined nanocomposites which are denoted, in terms of decreasing temperature at constant frequency, as Maxwell-Wagner-Sillars (MWS) effect merged with contribution from the DC conductivity, α-mode of POM, α-mode of PU, γ- and δ-modes of POM and γ-mode of PU. The dynamics of the recorded processes as well as the effect of the preparation technique, on the way these processes are imprinted in the dielectric spectra of the examined systems, are considered and discussed.