Quantum Efficiency of Spectral UV on Polyurethanes

Published

March 1, 2002

Author(s)

Tinh Nguyen, Jonathan W. Martin, E Byrd, E Embree

Abstract

Polyurethanes (PU) are used extensively as exterior building materials. However, PU undergoes degration during outdoor exposure. The quantum efficiency of spectral UV on photodegration of an acrylic-urethane coating has been investigated. Samples of approximately 8 m thick film applied to calcium fluoride substrates were prepared from a mixture of an acrylic polyol with an aliphatic triisocyanate. The UV source was two 1000 W xenon arch lamps, which produced radiation from 270 nm to 800 nm. Ten band pass filters, each having a specified wavelength range, were employed to provide different UV wavelength ranges from 290 nm to 540 nm. In addition, specimens exposed in the absence of UV and under 300 nm cut-on filters were also characterized. Exposure cells containing twelve windows (11 filters and one in the absence of light) corresponding to 12 specimens were used. All specimens were exposed to 50 C and at {difference} 0% relative humidity for more than eight months. The quantum efficiency of each wavelength range was estimated from data on degradation and total dosage absorbed in the film; both properties were measured by Fourier transform infrared spectroscopy and UV-visible spectroscopy, respectively. Both oxidation and chain scission were utilized to quantify PU phodegradation. Although there was no effect of wavelength on the degradation mechanism, both the rate and extent of degradation varied with dosage absorbed at different wavelength ranges. Except for the 290 nm filter, which had the highest value, quantum efficiency of other wavelength ranges did not differ greatly.

Proceedings Title

Proceedings of 9th International Conference on Durability of Buildings Materials and Components

Conference Dates

March 17-21, 2002

Conference Location

Brisbane, AS

Conference Title

International Conference on Durability of Building Materials and Components

Pub Type

Conferences

Keywords

building technology, coatings, degradation, FTIR, photodegradation, polyurethane quantum efficiency, UV, wavelength

Citation

Nguyen, T. , Martin, J. , Byrd, E. and Embree, E. (2002), Quantum Efficiency of Spectral UV on Polyurethanes, Proceedings of 9th International Conference on Durability of Buildings Materials and Components, Brisbane, AS (Accessed April 19, 2024)