Dynamics of model polycyclic aromatic hydrocarbon compound-epoxy composites: A dielectric study
| Autor: | Nicola Bowler, Daniel E. Bowen, Sabrina W. Torres, Rui Ding, Jamie M. Messman |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Arrhenius equation
Anthracene Materials science Polymers and Plastics Organic Chemistry Relaxation (NMR) Thermosetting polymer 02 engineering and technology Epoxy Dielectric Activation energy 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences chemistry.chemical_compound symbols.namesake chemistry visual_art Materials Chemistry visual_art.visual_art_medium symbols Composite material 0210 nano-technology Glass transition |
| Zdroj: | Polymer. 136:6-16 |
| ISSN: | 0032-3861 |
| Popis: | A model polycyclic aromatic hydrocarbon (PAH) compound, anthracene, was incorporated into a thermosetting epoxy matrix as a reinforcing moiety via physical dispersion and/or chemical modification. In order to understand the “additive effect” of glass transition temperature (Tg) observed with the variation of free anthracene (AN) and bonded 2-aminoanthracene (2-AM) loading, the relaxation dynamics were investigated by broadband dielectric spectroscopy. Within the measurement range of 0.01 Hz–1 MHz and −60 to 130 °C, three relaxation processes, namely normal mode (n-mode) relaxation, α relaxation, and β relaxation, were observed for all epoxy composites with bonded and/or unbound anthracene. After eliminating the strong effect of ionic conduction by using the logarithmic derivative approximation e ' ' ∝ ∂ e ' ∂ ln ω , derived from the Kramers-Kronig relations, the n-mode relaxation occurring at low frequencies above Tg for the rigid epoxy system is revealed. The Arrhenius diagram showing the temperature dependence of each relaxation process for the PAH-epoxy composites was obtained after parametric fitting using the Havriliak-Negami (HN) function in the frequency domain. The segmental α relaxation was more strongly impacted than the long-range n-mode relaxation by the different reinforcing approaches. The correlation of Tg -scaled fragility to molecular structures reveals the different mechanisms for the retardation effects on cooperative segmental and chain relaxation time. The localized β relaxation below Tg was not seemingly affected by the incorporation of bound and/or unbound anthracenes as indicated by the characteristic relaxation time and the activation energy. |
| Databáze: | OpenAIRE |
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