Effects of Spectral UV on Degradation of Acrylic-Urethane Coatings.
Effects of Spectral UV on Degradation of
Acrylic-Urethane Coatings.
(1251 K)
Nguyen, T.; Martin, J. W.; Byrd, E.; Embree, E. J.
Global Connectivity. FSCT 80th Annual Meeting Technical
Program. Proceedings. October 30-November 1, 2002, New
Orleans, LA, Federation of Socieites for Coatings
Technology, Blue Bell, PA, 2002.
Keywords:
coatings; degradation
Abstract:
Polyurethanes (PU) based on acrylic polyols are used
extensively as exterior coatings. However, these
materials undergo degradation during exposure to outdoor
environments. Although temperature, moisture, and other
weathering elements may contribute to the degradation of
polymer coatings, the primary cause of PU degradation
during outdoor exposure is ultraviolet (UV) light. For
that reason, the photo degradation mechanism of PU and
its model compounds have been studied extensively. Both
aromatic and aliphatic isocyanate-based polyurethanes
undergo chain scission by photo-oxidation process. It is
well known that photodegradation (photolysis and
photo-oxidation) of a material is determined by the
absorption characteristics of radiation in that
material. However, the absorption of radiation energy in
polymers is controlled by their chemical structure and
is dependent on radiation wavelength. Studies on
wavelength sensitivities of a variety of polymers have
been reviewed. However, little information is available
on the photo degradation behavior of PU with respect to
radiation wavelengths. The main objective of the present
study is to investigate the effects of different
radiation wavelengths from 290 nm to 525 nm on the
degradation mechanism and quantum efficiency of acrylic
polyol-based polyurethanes.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899