Study of Photodegradation of Epoxy Polymer by Using Slow Positron Annihilation Spectroscopy
R Zhang, Xiaohong Gu, H Chen, J Zhang, Y Li, Tinh Nguyen, T C. Sandreczki, Y C. Jean
Slow positron annihilation spectroscopy (SPAS) has been used to study the early stage of epoxy photodegradation. Spin-coated samples of a crosslinked epoxy were prepared by stoichiometrically mixing a diglycidyl ether of bisphenol A epoxy resin with 1,3-bis(aminomethyl) cyclohexane. Samples having a thickness of approximately 12 mm were exposed in a QUV-340 chamber with an intensity of 0.85 W/m2.nm for up to 352 h. They were removed and analyzed periodically using a variable energy positron beam at University of Missouri-Kansas City. The S parameter, which is calculated from the Doppler broadening of energy spectra, is used to characterize degradation. The depth profile of degradation for different irradiation periods and the time dependence of photodegradation at different depths were measured. The degradation depth was found nearly independent of irradiation time, and the half-life of the photodegradation reactions varied linearly with sample depth. The detectable half-lifetime of this amine-cured epoxy by SPAS was quite short, on the order of 100 h near the surface. The results suggest that SPAS is an useful technique to detect early stage of polymer degradation.
, Gu, X.
, Chen, H.
, Zhang, J.
, Li, Y.
, Nguyen, T.
, Sandreczki, T.
and Jean, Y.
Study of Photodegradation of Epoxy Polymer by Using Slow Positron Annihilation Spectroscopy, Journal of the American Chemical Society
(Accessed February 29, 2024)