Dynamic mechanical investigations of the effects of water sorption and physical ageing on an epoxy resin system

After immersion (3 months) in distilled water, the epoxy-amine (diglycidyl ether of Bisphenol A-4,4'-methylene bis[3-chloro-2,6-diethylaniline], DGEBA-MCDEA) samples were mounted on the dynamic mechanical analyser where the thermal ageing treatment was performed. The influence of both hydrothermal and physical ageing on the viscoelastic properties of DGEBA-MCDEA network was investigated. Three relaxational processes were evidenced on the mechanical spectra (at 1 Hz) of the samples: the main relaxation (alpha) at higher temperatures, the secondary relaxation (beta) at lower temperatures, and the intermediate omega-relaxation between 300 and 350 K. The beta-relaxation mode was found bimodal, mainly affected by the water sorption, and unconcerned by the structural recovery following the thermal ageing treatment. On the opposite, the viscoelastic characteristics of the omega-relaxation were significantly affected by each step of both hydrothermal and thermal ageing treatments. (C) 2002 Elsevier Science Ltd. All rights reserved.