Design of the Ultimate Behavior of Tetrafunctional Epoxies Modified with Polysulfone by Controlling Microstructure Development

P. A. OYANGUREN; B. AIZPURUA; M.J. GALANTE; C.C. RICCARDI; O. CORTAZAR; I. MONDRAGÓN,

JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS

JOHN WILEY & SONS INC

Lugar: New York; Año: 1999 vol. 37 p. 2711 - 2725

0887-6266

The reaction-induced phase separation in a tetrafunctional epoxy?cyclicanhydride system modified with polysulfone (PSF) was followed by optical microscopy(OM), light scattering (LS), and scanning electron microscopy (SEM). The selectedsystem was N,N,N9,N9-tetraglycidyl-4,49-diamino diphenylmethane cured with methyltetrahydrophthalic anhydride, in the presence of variable PSF concentrations. Thedifferent experimental techniques allow us to establish the phase separation mechanism.For modifier concentrations close to the critical point, 10 and 15 wt % PSF, phaseseparation proceeded by spinodal demixing (SD). For a modifier concentration muchlower than the critical point, 5 wt % PSF, phase separation occurred via the nucleationand growth (NG) mode. For 7.5 wt % PSF, depending on the cure temperature, SD orNG was observed. Dynamic mechanical behavior of the resulting materials had beendiscussed based on fractionation of different species during the phase separationprocess. The fracture toughness increased significantly when bicontinuous (10 wt %PSF) or phase-inverted (15 wt % PSF) structures were generated. For mixtures containing15 wt % PSF, the dependence of fracture toughness on the stoichiometric ratio(anhydride groups/epoxy groups) was analyzed.