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 gamma mode at about -150 degrees C and a beta mode at -100 degrees C. The existence of two polarization phenomena beta /sub 2/ and beta /sub 1/ shows that the beta relaxation is complex. Above room temperature, the relaxation mode associated with the glass transition has been observed at 100 degrees 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 tau /sub O/ is characteristic of the matrix filler interface/interphase.<>