Rubber‐modified epoxies. II. A reaction‐induced phase separation observed in‐situ and a posteriori with different methods

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Abstract
The reaction‐induced phase separation in epoxy systems modified with rubber was firstly observed in situ with small angle X‐ray scattering (SAXS), light transmission (LT), light scattering (LS), scanning electronic microscopy and transmission electronic microscopy techniques. The different observation windows of the SAXS, LT and LS methods allow us to follow the phase separation at two size levels. The selected system was bisphenol‐A diglycidylether cured with 4,4′‐diamino‐3,3′‐dimethyldicyciohexylmethane, in the presence of 15% wt of epoxy‐terminated butadiene acrylonitrile random copolymers of different molecular weights. The phase separation inside the particles formed was followed first. Influences of precure temperature, rubber molecular weight, the postcure, vitrification and gelation on the evolution of the structure inside the particles are discussed. The real beginning of the phase separation is also discussed.