Mechanism of Epoxy Moisture Effects
Abstract
The loss of mechanical properties of resin matrix composites at elevated temperatures which occur following absorption of atmospheric moisture is considered a reversible phenomenon caused by the plasticizing effect of the absorbed water. At the molecular level, these losses could be attributed to the disruption of interchain hydrogen bonding by water molecules. Based on mechanochemical considerations, the possibility for occurrence of irreversible stress-induced chemical changes in epoxy polymers exposed to humid environments is the main objective of this study. Internal reflectance Fourier transform infrared (FT-IR) spectra of tetraglycidyl diaminodiphenyl methane (TGDDM) cured with diaminodiphenyl sulfone (DDS) obtained before and after exposure to the combined effect of stress, elevated temperature, and moisture (STM), elevated temperature and moisture (TM) or stress and elevated temperature (ST) environments were used to obtain comparative evidence for irreversible chemical changes. The results of eight different experiment series provide spectroscopic evidence indicating that exposure of epoxy specimens to STM and TM environments which greatly exceed anticipated service conditions leads to detectable rupture of chemical bonds in the polymer network. Internal swelling stresses are believed responsible for the observed bond cleavages. Spectral evidence indicates that, as expected, post-cure reactions are the most prominent chemical changes induced by exposure of epoxy specimens to the ST, SM, M and T environments. The infrared intensities of the bands attributed to the sulfone group are sensitive to chemical changes which suggests their potential use as molecular monitors within the epoxy network.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1977
- Accession Number
- ADB019634
Entities
People
- R. L. Levy