INVESTIGADORES
SOULE Ezequiel Rodolfo
congresos y reuniones científicas
Título:
Polimerization-Induced Phase Separation in an Epoxy Network Modified with a Polyedral Oligomeric Silsesquioxane
Autor/es:
CARLA DI LUCA; ILEANA A. ZUCCHI; LAURA A. FASCE; CRISTINA E. HOPPE; EZEQUIEL R. SOULÉ; ROBERTO J. J. WILLIAMS
Reunión:
Congreso; SLAP 2010; 2010
Resumen:
The dispersion of intercalated/exfoliated
clays in polymers impart some desired properties to the neat matrix,
such as a decrease in permeability due to geometrical effects and an
increase in the fire resistance due to the inorganic character of the
clay. However, processing is difficult mainly due to the high
viscosities of the starting dispersions. In this manuscript we explored
the possibility of producing a dispersion of crystalline platelets
in-situ during polymerization, starting from homogeneous solutions. For
this purpose, we replaced the clays with polyhedral oligomeric
silsesquioxanes (POSS) because they can be dissolved in adequate polymer
precursors and can be phase-separated in the course of polymerization.
The aim was to find conditions were a crystal-liquid (C-L) phase
separation could take place instead of a conventional L-L phase
separation. The in-situ generation of POSS crystalline platelets can
impart similar characteristics to those observed clay-modified polymers
with the advantage of a much easier processing. The selected
formulation was based on glycidyloxypropyl-heptaisobutyl POSS dissolved
in a stoichiometric mixture of diglycidyl ether of bisphenol A (DGEBA) and 4,4-methylenebis(2,6-diethylaniline)
(MDEA). In a specific range of POSS concentrations and polymerization
temperatures, a C-L phase separation was observed generating POSS
crystalline platelets with sizes in the range of the micrometers.
Following this primary phase separation, a dispersion of POSS-rich
droplets was produced when the residual liquid phase entered the L-L
immiscibility region. The final material exhibited a dual dispersion of
POSS platelets and spherical POSS-rich domains uniformly dispersed in
the matrix. A thermodynamic model enabled to provide an explanation of
the experimental observations.