In recent years, there has been increasing interest in
the use of fiber-reinforced polymer (FRP) composites in
building and construction due to the many advantages
offered by composite materials. Among these advantages
are excellent corrosion and fatigue resistance and
high strength-to-weight ratio. However, the outdoor
environment contains elements that are destructive to
organic polymers, such as moisture, acid rain, temperature
cycling, and ultraviolet (UV) radiation. UV radiation,
in particular, is known to be highly damaging to
organic polymeric materials.
The primary objective of this study was to investigate
the chemical and mechanical effects of UV radiation on
vinyl ester, a thermosetting polymer commonly used in
building and construction applications. Effects of exposure
to UV radiation generated by a 1000 W xenon arc
source were characterized by tensile testing, atomic
force microscopy (AFM), Fourier transform infrared
spectroscopy (FTIR), and X-ray photoelectron spectroscopy
(XPS). Nanoindentation was performed with the
AFM on exposed and unexposed specimens to measure
changes in hardness and Young’s modulus in the
exposed surface. The AFM was also used to monitor
changes in the surface morphology at the nanoscale.
These mechanical, chemical, and microscopy analyses
were used to obtain an understanding of how this resin
system degrades under exposure to UV radiation, and
to determine the effects of UV exposure on bulktensi le
properties.