Dielectric analysis of the linear polymerization of an epoxy resin

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 °C. 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. © 2001 Society of Chemical Industry

Physical properties of epoxy resin/titanium dioxide nanocomposites

“…Interestingly, in the composites with higher filler loadings (3 and 4 wt%), the decreased T g caused the α relaxation to shift towards lower temperatures and to merge with the β relaxation, forming a broad αβ relaxation. Similar behavior has been observed by dielectric relaxation spectroscopy on the curing kinetics [50, 51]. The β mode was found to weakly depend on the curing degree of the epoxy network, whereas the dynamics of the α relaxation become faster at low curing degrees and merge with the local β relaxation.…”

Physical and chemical vitrification: the role of configurational entropy

“…(2). It provides evidence that the s max (a) behavior is accounted for by an expression like the Vogel-Fulcher form, originally proposed in similar systems through a phenomenological [9,10] or a semi-empirical T g -based approach [11]. More importantly, the results in Table 1 meet our expectations for the values of the a 0 parameter.…”

Kinetic study of epoxy curing in the glass fiber/epoxy interface using dansyl fluorescence

“…To do this kind of study, different techniques have been used, such as FTIR [1][2][3][4], DSC [4][5][6][7], DEA [22,23], and rheometry [24]. All of them, at least, allow the obtaining of a global kinetic equation and the apparent kinetic parameters such as the activation energy of the processes.…”