Synergetic Effect of Triglycine Sulfate and Graphite Nanoplatelets on Dielectric and Piezoelectric Properties of Epoxy Resin Composites

Epoxy resin composites with 30 wt% of triglycine sulfate (TGS) and up to 1 wt% of graphite nanoplatelets (GNP) were fabricated and studied by means of broadband dielectric spectroscopy (20 Hz-3 GHz). It was demonstrated that the dielectric properties are mainly governed by the Maxwell-Wagner relaxation at lower frequencies (below 1 MHz) and by diffuse ferroelectric soft mode at higher frequencies (above 1 MHz). The ferroelectric origin of the phase transitions was also confirmed by piezoelectric investigations. Although the phase transition temperature is independent of GNP concentration, the piezoelectric and dielectric (above 1 MHz) properties of composites are strongly improved by GNP in a broad temperature range. This gives evidence for the strong synergy between GNP and ferroelectric particles. The synergy effect appears due to the better distribution of TGS particles in ternary composites and the creation of electric fields by GNP inside the composite. (C) 2018 Society of Plastics Engineers