Investigation of phase morphology of polyetherimide-toughened epoxy resin by scanning probe microscopy

High resolution nanomechanical analysis in combination with high resolution topography imaging was used to investigate the phase morphology of a polyetherimide-toughened tetra-functional epoxy resin. A two-phase structure close to co-continuous morphology is observed. Here, polyetherimide and epoxy-rich regions can be clearly identified due to their different nanomechanical properties. Within the PEI-rich regions, the high resolution testing allows identification of polyetherimide-rich globules with a size between 50 nm and 500 nm, in addition to the well-known epoxy-rich rounded substructures with a diameter of about one micrometer. Etching influences the surface elastic properties and results in an increase of the epoxy surface modulus. Surface ageing results in a slight increase of the surface modulus.