Dielectric relaxation phenomena in model composites

Thermally stimulated current spectroscopy has been applied to the study of interfaces/interphases in composites. Three DGEBA-DDA matrix model samples have been studied. Below room temperature, two relaxation modes are observed in all samples: a γ mode at about -150°C and a β mode at -100°C. The existence of two polarization phenomena β₂ and β₁ shows that the β relaxation is complex. Above room temperature, the relaxation mode associated with the glass transition has been observed at 100°C. The analysis of its fine structure indicates that it is constituted of elementary processes characterized by relaxation times following a compensation law. For the upper activation enthalpies, the response of the matrix and of the two composites is analogous. For the lower activation enthalpies, the slope of the compensation line is modified. In fact, for a given enthalpy, the pre-exponential factor τ_O is characteristic of the matrix filler interface/interphase