The dielectric properties of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin and n-butylamine have been studied in the frequency range 100 Hz to 3 GHz at 25 degreesC. The unreacted mixture showed a single relaxation which gradually split in two relaxations, the separation of which increased as the reaction progressed. The low and high frequency relaxations are attributed to the structural dynamics of the growing macromolecules and to the motions of the dipoles associated with the monomers, respectively. The increase of the structural relaxation time is described by a phenomenological relationship, similar to the Williams-Landel-Ferry equation, that allows estimation of the conversion at vitrification. A marked decrease of the electrical conductivity has also been observed, as a result of the increasing viscosity of the system. The conductivity and the structural relaxation time are correlated by means of a generalized Debye-Stokes-Einstein model. It has also been found that both components of the complex dielectric permittivity, measured at microwave frequencies, yield information on the advancement of the polymerization process.
Dielectric Analysis of the linear Polymerization of an Epoxy Resin
COREZZI, Silvia
2001
Abstract
The dielectric properties of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin and n-butylamine have been studied in the frequency range 100 Hz to 3 GHz at 25 degreesC. The unreacted mixture showed a single relaxation which gradually split in two relaxations, the separation of which increased as the reaction progressed. The low and high frequency relaxations are attributed to the structural dynamics of the growing macromolecules and to the motions of the dipoles associated with the monomers, respectively. The increase of the structural relaxation time is described by a phenomenological relationship, similar to the Williams-Landel-Ferry equation, that allows estimation of the conversion at vitrification. A marked decrease of the electrical conductivity has also been observed, as a result of the increasing viscosity of the system. The conductivity and the structural relaxation time are correlated by means of a generalized Debye-Stokes-Einstein model. It has also been found that both components of the complex dielectric permittivity, measured at microwave frequencies, yield information on the advancement of the polymerization process.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
