Dynamics of model polycyclic aromatic hydrocarbon compound-epoxy composites: A dielectric study

POLYMER

卷:136

Article

Ding, Rui¹  Torres, Sabrina W.²  Messman, Jamie²  Bowen, Daniel E.²  Bowler, Nicola¹ 

[1] Iowa State Univ, Dept Mat Sci & Engn, Ames, IA 50011 USA

[2] Honeywell FM&T LLC, Dept Energys, Natl Security Campus, Kansas City, MO USA

关键词: PAH-Epoxy composites;    Dielectric relaxation;    Glass transition;   

DOI  :  10.1016/j.polymer.2017.12.035

来源: Elsevier

【 摘 要 】

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 degrees C, three relaxation processes, namely normal mode (n-mode) relaxation, a relaxation, and beta 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 epsilon (sic) partial derivative epsilon'/partial derivative In omega, derived from the Kramers-Kronig relations, the n-mode relaxation occurring at low frequencies above T-g 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 a relaxation was more strongly impacted than the long-range n-mode relaxation by the different reinforcing approaches. The correlation of T-g -scaled fragility to molecular structures reveals the different mechanisms for the retardation effects on cooperative segmental and chain relaxation time. The localized b 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. (c) 2017 Elsevier Ltd. All rights reserved.

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