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Interplay between Mechanical Fatigue and Network Structure and Their Effects on Mechanical and Electrical Properties of Thin Silicone Films with Varying Stoichiometric Imbalance
Author(s) -
Zhang Mengjia,
Denes Istvan,
Buchmeiser Michael R.
Publication year - 2016
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201600041
Subject(s) - materials science , silicone , composite material , permittivity , silicone oil , dielectric , modulus , copolymer , elastic modulus , stoichiometry , dynamic mechanical analysis , polymer , polymer chemistry , chemistry , organic chemistry , optoelectronics
Thin silicone films for applications as dielectric electroactive polymer (DEAP) are fatigued under mechanical cycling (Wöhler tests) until rupture. The silicones are based on linear vinyl‐terminated poly(dimethylsiloxane) (PDMS) cross‐linked with tetrafunctional methylhydrosiloxane–dimethylsiloxane copolymer. Stoichiometric imbalance of the hydrosilane to vinyl groups is varied (1.3, 1.7, and 3). Complementary, all silicones are compounded with silicone oil (55 wt%) and silica (4.5 wt%). Changes in cross‐linking density, elastic modulus, dielectric permittivity, and dielectric breakdown are examined. The fatigued specimens show increased cross‐linking density due to mechanically induced secondary cross‐linking of excessive hydrosilane groups. This leads to significant changes in the elastic modulus and permittivity of the material, which can negatively affect the performance of the DEAP device. The “ critical loading conditions ,” where the fatigued specimens show maximum changes in properties, are found to depend on excess hydrosilane content.