Epoxy Resin (DGEBA/TETA) Exposed to Water: a Spectroscopic Investigation to Determine Water-Epoxy Interactions

Epoxy resin, diglycidyl ether of bisphenol A (DGEBA) and triethylenetetramine (TETA), is known to be hygroscopic in nature, which eventually leads to mechanical performance degradation of the material. The long-standing debate on the nature of water-epoxy interaction has been investigated in this study with the help of terahertz spectroscopy, which is able to probe sub 100 cm− 1 wavenumbers in which hydrogen bonds of water are active as well as infrared spectroscopy, which is able to probe 600–1000 cm− 1 in which the libration motions of the water molecules are dominant. Based on observations, it can be demonstrated that both hydrogen-bonded water (with epoxy) and free interstitial water (hydrogen-bonded with itself) is present when the epoxy resin is exposed to normal or saline water. A schematic diagram is presented to demonstrate epoxy-water interactions.