Morphology and phase composition of an amine cured rubber modified epoxy

Abstract

The sharpness of the interface between the matrix and the dispersed phase, the volume fraction of the dispersed phase, the distribution of particle sizes, and the concentration of epoxy in the dispersed phase were determined. Scanning transmission electron microscopy coupled with energy dispersive x-ray analysis revealed that the interface width is less than 500 A. Variation of the fraction of mobile hydrogens with temperature determined by nuclear magnetic resonance indicated that a small fraction of segments participated in mixing at the interface. Differential scanning calorimetry and nuclear magnetic resonance indicated that all the rubber precipitates as a discrete phase. The distribution of particles greater than 0.1 ..mu..m in diameter was measured, and the average diameter of these particles was found to be 0.8 ..mu..m. The particles larger than 0.1 ..mu..m accounted for approximately 50% of the total volume of dispersed phase. The epoxy concentration in the dispersed phase was determined using /sup 13/C nuclear magnetic resonance spectroscopy. This concentration was found to be less than that predicted if all the epoxy monomer units attached to the rubber molecules were present in the dispersed phase