INVESTIGADORES
HOPPE Cristina Elena
artículos
Título:
In-Situ Generation of a Dispersion of POSS Crystalline Platelets in an Epoxy Matrix Induced by Polymerization
Autor/es:
C. DI LUCA; E. R. SOULÉ; I. A. ZUCCHI; C. E. HOPPE; L.A. FASCE; R.J.J. WILLIAMS
Revista:
MACROMOLECULES
Editorial:
AMER CHEMICAL SOC
Referencias:
Año: 2010 vol. 43 p. 9014 - 9021
ISSN:
0024-9297
Resumen:
he 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 where 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 in clay-modified polymers
(except for the nanoscopic size of thickness), 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.