Influence of absorbed water on the dielectric properties and glass-transition temperature of silica-filled epoxy nanocomposites

• Published in: 2006 IEEE Conference on Electrical Insulation and Dielectric Phenomena pp. 321 - 324
• Main Authors: Zou, C., Fu, M., Fothergill, J.C., Rowe, S.W.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.10.2006
• Subjects: Delamination; Dielectric measurements; Electrochemical impedance spectroscopy; Epoxy resins; Frequency; Humidity; Nanocomposites; Silicon compounds; Temperature; Water
• ISBN: 1424405467; 9781424405466
• ISSN: 0084-9162
• DOI: 10.1109/CEIDP.2006.311934

Work on dielectric spectroscopy of epoxy resin filled with nano-SiO 2 at different relative humidities and temperatures is reported. Above the glass-transition temperature (T g ), dc-like imperfect charge transport (QDC or LFD) dominates the low frequency dielectric spectrum. Another mid-frequency relaxation process was found in the non-dried composites. Water also induces glass-transition temperature decreases, which can be measured both by dielectric spectroscopy and DSC. Both theory and experiment demonstrated that a higher water content could exist in nanocomposites than unfilled epoxy suggesting a bigger free volume when nanostructured. In our system, the hydrophilic surface of silica is likely to cause water to surround and lead to delamination of the epoxy from SiO 2 . This is a potential mechanical and dielectric weakness in the nanocomposites, which may lead to an ageing phenomenon. Hydrophobic surface group may reduce the water adsorption in nanocomposites.