Estimation of Absorbed Photolytic Dosage and Quantum Yield Using UV-VIS and FTIR Spectroscopies.
Estimation of Absorbed Photolytic Dosage and Quantum
Yield Using UV-VIS and FTIR Spectroscopies.
Martin, J. W.; Nguyen, T.; Byrd, W. E.; Embree, N.
Spring Meeting. Volume 82. American Chemical Society.
PSME. Proceedings. March 26-30, 2000, San Francisco,
CA, 373-374 pp, 2000.
FT-IR; spectroscopy; coatings; degradation; effective
dosage; quantum yield; UV spectroscopy
An effective dosage model has been introduced for
predicting the service life of polymeric materials
exposed to UV light. The effective dosage model, which
relates material damage through the apparent quantum
yield, has a firm basis in the priciples of
photochemistry. The primary inputs into this model are
radiation dosage absorbed in the material and material
damage, and the outputsare effective dosage and apparent
quantum yield. Laboratory experiments were designed to
provide data on these parameters over wide ranges of
conditions to encompass those environments to which a
coating is expected to be exposed in the field and to
allow the effects of competing degradation reactions to
be separated. UV visible spectroscopy and FTIR
spectroscopy were used to measure absorbed dosage and
damage in the coatings, respectively. Estimates of the
absorbed dosage and apparent quantum yield were found to
be very sensitive to initial UV-visible absorption of
the coatings, coating degradation products, anomalous UV
absorption of the substrate, spectral handling of
infrared and UV-visible spectra, and the reproducibility
of UV-visible and FTIR spectrometers.