Dielectric properties of an epoxy resin during polymerization

Abstract

SynopsisDielectric measurements were utilized in the investigation of the polymerization of epoxy resin Epon 826 with diethylenetriamine (DETA) as the crosslinking agent. The time variation of the dissipation factor and of the dielectric constant were measured continuously, while the epoxy system was held at a constant temperature. A range of 11 frequencies (330 cycles/sec.-10 Mcycles/sec.) at three different polymerization temperatures (30, 45, SOOC.) was covered. The test results are given as a set of curves for the dissipation factor and the dielectric constant versus time. Nearly all the dissipation factor curves have the same characteristic shape, with a well-dehed minimum (valley) followed by a maximum (peak). The dielectric constant fa& monotonously from a high initial value to a small h a 1 one that is specific for the fully cured resin. If the time at which the dissipation factor reaches the valley t, and the peak tp are plotted versus the logarithm of the frequency, two straight lines will be obtained. Such a plot can be utilized as an aid in controlling the curing process of cast resins.

Electrical properties of an epoxy resin during and after curing

“…In Table I11 tYl denotes the instant when the time dependence of a.c. conductivity begins to be nearly linear in the log y--t plot and tYz denotes the instant when it begins to deviate from straight l i e and to be governed by eq. (8). The values of tY1 are in good agreement with gelation times t,P to which a relative concentration of epoxy groups of 0.48 corresponds, and the tY2 values with times of tan 6 (50 Hz) peaks when c/co is approximately 0.27.…”

“…6), however, the function y J t ) is linear within longer periods. This part of the dependence may be expressed as follows y-= (K,'t)-" (8) where K,' is a certain parameter characterizing the rate of conductivity change. Values of K,' are given in Table I and in Figure 18; the corresponding activation energy is E, = 13.5 kcal/mole.…”

Prospects of microwave processing: An overview

“…epoxy resin, glass fibre reinforced epoxy composite, carbon fibre reinforced epoxy composite, poly-ether-ether-ketone (PEEK) coating, SiC particle reinforced PEEK coating (Haran et al 1965;Lee and Springer 1984;Chen et al 1993;. epoxy resin, glass fibre reinforced epoxy composite, carbon fibre reinforced epoxy composite, poly-ether-ether-ketone (PEEK) coating, SiC particle reinforced PEEK coating (Haran et al 1965;Lee and Springer 1984;Chen et al 1993;.…”

Prospects of microwave processing: An overview

“…epoxy resin, glass fibre reinforced epoxy composite, carbon fibre reinforced epoxy composite, poly-ether-etherketone (PEEK) coating, SiC particle reinforced PEEK coating (Haran et al 1965;Lee and Springer 1984;Chen et al 1993;Zhang G et al 2006). Dipole structure, frequency of processing, selective coupling, fabrication temperature, chemical nature of additives and fillers etc all influence the processing (Thostenson and Chou 1999).…”