Epoxy-diamine thermoset/thermoplastic blends: Dielectric properties before, during, and after phase separation

Frequency dependent dielectric measurements have been used to monitor the c omplex chemical, composition and morphological changes occurring during cur e of a high-temperature epoxy-amine (DGEBA-MCDEA) polyetherimide (PEI) blen d. The dielectric measurements are able to monitor in situ the reaction adv ancement before phase separation, the onset of phase separation, the Maxwel l-Wagner-Sillars (MWS) effect, and the buildup in T-g in both the continuou s thermoplastic PEI-rich phase and the occluded epoxy-rich phase. The MWS p redicted values were in relatively good agreement with the experimental val ues and suggest a nonspherical shape. The conductivity in the homogeneous b lend decreased much more rapidly than expected based on concentration and c hange in viscosity, suggesting that the conduction mechanism in the homogen eous blend is strongly affected by the proximity of the hydrogen-bonding gr oups in the epoxy amine.