On the Dielectric Behavior of Amine and Anhydride Cured Epoxy Resins Modified Using Multi-Terminal Epoxy Functional Network Modifier

Abstract

A range of modified amine- and anhydride-cured epoxy systems based upon diglycidyl ether of bisphenol A was produced, through the systematic incorporation of moieties termed functional network modifiers (FNMs) that serve to change the network structure in controlled ways. Here, the chosen FNM was trimethylolpropane triglycidyl ether (TTE). The resulting materials were characterized by Fourier transform infrared spectroscopy, thermal analysis, dielectric spectroscopy and measurements of direct current conduction. A progressive reduction in the glass transition temperature of the modified samples was seen with increasing TTE, which is interpreted in terms of changes in the network architecture of the resin. The molecular origins of the dielectric and relaxation processes are proposed. The observed increase in conduction seen exclusively with increasing TTE content in the amine-cured systems is considered in terms of the chemistry of the FNMs, variations in free volume, changes in molecular dynamics and residual unreacted groups retained from the curing reaction. Specifically, we relate the observed increase in conduction to the presence of unreacted amine groups.

Dielectric analysis of water uptake in polymer coating using spatially defined Fick's law and mixing rule

“…Using previous parameters from gravimetric analysis (diffusion coefficient D and relative maximal mass uptake ratio X M | ∞ - Table 1) as well as additional values listed in Table 2 3 leads to results depicted in Figure 8, where the experimental equivalent permittivities have been obtained by multiplying the measured capacitance by the mean sample thickness and inverse electrode surface, yielding polymer coating equivalent permittivity in the same range than reported values in the literature ( [44,45] Cole-Cole coefficient α sec 0.87 Table 2: Additional parameters for dielectric analysis ( 0 denotes the vacuum permittivity). due to the limited decreasing slope with frequency (consistent with the literature - [23,20]), but it should be kept in mind that the use of such a permittivity model does not have any impact on the exposed principles and can be advantageously replaced by another one (note that the same observation also applies for the mixing rule or for the evolution of the water mass uptake; the latter being possibly non-Fickian).…”

Investigation of the functional network modifier loading on the stoichiometric ratio of epoxy resins and their dielectric properties

“…As such, the strength of this absorption band should be determined by the cumulative effect of the aromatic ether groups in the DER 332, the aliphatic ethers within the POSS structure plus any ethers formed during curing. Absorbance at 1040 cm -1 has, similarly, been associated with the stretching of both (a) aromatic ethers [28] and (b) aliphatic ethers [24].…”

“…Figure 8c shows the dependence of the imaginary part of the relative permittivity, e'', on the formulation for the X EG% GPOSS sample set. The peak in the imaginary permittivity observed at frequencies above 10 4 Hz is commonly attributed to the epoxy brelaxation [37,[52][53][54] which, in amine-cured systems, originates from the motion of hydroxyl groups formed during cross-linking, together with a degree of cooperativity from the cross-links' surrounding structure [28]. From the FTIR data presented in Fig.…”

Development of Sustainable High Performance Epoxy Thermosets for Aerospace and Space Applications

“…Analyzing the FTIR spectra, we can observe a clear evolution and change in four main areas, their graphical representations being present in Figure 4. During epoxy-anhydride crosslinking through polyesterification and/or polyetherification reactions, -OH groups may be produced when using DMP 30 as an initiator [31][32][33][34][35]. As can be seen in Figure 4a, the stretching vibration peak of -OH found at 3589 cm −1 increased in intensity with increasing temperature, a phenomenon attributed to the generation of hydroxyl groups during the ring opening reaction of the epoxy group.…”