Thermosetting polymers are frequently used in formulations, including rubbers, thermoplastic polymers or oils, etc, in an amount of the order of 2–50 wt% with respect to the thermoset. This extra component, called the modifier, may initially be immiscible or may phase-separate during cure. This last process, i.e the reaction-induced phase separation, is the subject of this review. A thermodynamic description of the process is made, using the Flory-Huggins equation at two approximation levels, i.e. a quasi-binary approach and a multicomponent treatment taking polydispersity of constituents into account. Thermodynamic factors affecting the phase separation process are thus established. Nucleation and growth (NG) and spinodal demixing (SD) are considered as possible phase separation mechanisms. Factors promoting one or the other process are discussed. The control of morphologies generated is analyzed on the basis of thermodynamic and kinetic arguments. Ideas for obtaining particular morphologies enhancing particular properties are put forward.

Reaction-induced phase separation in modified thermosetting polymers

Influence of epoxy hardener on miscibility of blends of poly(methyl methacrylate) and epoxy networks

The study reported in this thesis concerns the relationship
between morphology and the properties of multicomponent
epoxy and methacrylate resins.
The thermodynamic and kinetic aspects of phase separation in
reactive, thermosetting, systems are explored and applied to
the investigation of blends of 'high performance' epoxy
resins with polyethersulphone. The mechanical properties of
the same cured blends are shown to be insensitive to
considerable variations in composition, cure and the
resulting morphology, both in the bulk-resin and in carbon
fibre-epoxy laminate forms.
Room temperature fracture and yield behaviour of highly
cross linked and rubber modified methacrylates, of rubber
modified dysfunctional epoxies, as well as of the above
mentioned epoxy/polyether sulphone blends, is investigated.
Special emphasis is placed on a comparison of the kinetics
of tensile creep between the different systems. Loss of
ductility in the highly cross linked resins is shown to
result in a very limited scope for toughness enhancement by
the usual rubber toughening methods.

Isabelle Quintard

Papers

Phase separation from solutions of poly(ether sulfone) in epoxy resins