Epoxy-Diamine Thermoset/Thermoplastic Blends:  Dielectric Properties before, during, and after Phase Separation

Abstract

Frequency dependent dielectric measurements have been used to monitor the complex chemical, composition and morphological changes occurring during cure of a high-temperature epoxyamine (DGEBA-MCDEA) polyetherimide (PEI) blend. The dielectric measurements are able to monitor in situ the reaction advancement before phase separation, the onset of phase separation, the MaxwellWagner-Sillars (MWS) effect, and the buildup in T g in both the continuous thermoplastic PEI-rich phase and the occluded epoxy-rich phase. The MWS predicted values were in relatively good agreement with the experimental values and suggest a nonspherical shape. The conductivity in the homogeneous blend decreased much more rapidly than expected based on concentration and change in viscosity, suggesting that the conduction mechanism in the homogeneous blend is strongly affected by the proximity of the hydrogen-bonding groups in the epoxy amine.

Dielectric Analysis (DEA)

“…If the ionic concentration does not change during cure, then σ DC is directly proportional to ion mobility. This provides a plausible explanation for a σ DC ∝ η − x dependence with 0.42 ≤ x ≤ 0.70, frequently observed in such systems (Eloundou et al 1998a,b ;Bonnet et al 2000 ;Krouse et al 2005 ) from the beginning of the reaction up to a conversion limit lower than the gel point α gel . Using a combination of ion time -of -fl ight and dielectric measurements, Krouse et al (2005) measured separately the two components of the conductivity, ion mobility, and number of mobile charge carriers, in an unreacted DGEBA/MCDEA system and during buildup in the network structure during cure over a similar range of viscosities.…”

Vitrification, devitrification, and dielectric relaxations during the non‐isothermal curing of diepoxy‐cycloaliphatic diamine

“…The conductive and dipolar response of an epoxy‐amine system has been extensively studied in isothermal regime. For a brief reference we might cite the review by Johari13 and the work of Tombari et al,14 Williams and coworkers15, 16 and several other authors 17–21. Under isothermal conditions, a peak in ε″ appears, which tends to shift to higher reaction times as the measuring frequency decreases, due to the increase in the dipolar relaxation time as the reaction progresses.…”

Effect of Attapulgite Nanorods and Calcium Sulfate Microwhiskers on the Reaction-Induced Phase Separation of Epoxy/PES Blends

“…It has been generally accepted that phase separation plays a significant role in determining the morphology and properties of polymer mixtures. The reaction-induced phase separation in thermosets/thermoplastic blend is a very important physical/chemical process, which has aroused wide interest for many years [1][2][3][4][5][6][7][8][9][10][11][12].…”