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Estimation of Absorbed Photolytic Dosage and Quantum Yield Using UV-VIS and FTIR Spectroscopies.


pdf icon Estimation of Absorbed Photolytic Dosage and Quantum Yield Using UV-VIS and FTIR Spectroscopies. (519 K)
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.

Keywords:

FT-IR; spectroscopy; coatings; degradation; effective dosage; quantum yield; UV spectroscopy

Abstract:

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.