Hygrothermal aging of rubber-modified and mineral-filled dicyandiamide-cured DGEBA epoxy resin. III. Dielectric spectroscopy investigation

Katya I. Ivanova, Richard A. Pethrick, Stanley Affrossman

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

The effects of moisture absorption on the dielectric properties of a rubber-modified, mineral-filled, epoxy resin based on the diglycidyl ether of bisphenol A cured with dicyandiamide are reported. Samples of the resin were aged by immersing in deionized water, or 5% w/w NaCl solution, at elevated temperatures. Dielectric measurements were carried out over the frequency range 10 (1) to 6 X 10(5) Hz. A featureless dielectric spectrum was observed with both real and imaginary dielectric permittivity increasing with the amount of absorbed water. The change in the dielectric properties with absorption of water was independent of presence of salt, temperature of exposure, and aging history, although a hysteresis of the hydration- dehydration process was observed at low frequencies. Two types of absorbed water were observed-water molecularly dispersed within the epoxy matrix and clustered water in spherical microcavities. The time dependence of the real dielectric permittivity measured at 10 kHz was found to closely resemble that of the water absorption, which allowed the activation energy of diffusion to be calculated from both dielectric and gravimetric data.
Original languageEnglish
Pages (from-to)1011-1024
Number of pages13
JournalJournal of Applied Polymer Science
Volume84
Issue number5
DOIs
Publication statusPublished - 2 May 2002

Keywords

  • dielectric properties
  • aging
  • epoxy resin
  • water absorption
  • microcavity formation

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