Effects of Ultraviolet Radiation Exposure on Vinyl Ester Resins: Characterization of Chemical, Physical and Mechanical Damage.
Effects of Ultraviolet Radiation Exposure on Vinyl Ester
Resins: Characterization of Chemical, Physical and
Mechanical Damage.
(553 K)
Signor, A. W.; VanLandingham, M. R.; Chin, J. W.
Polymer Degradation and Stability, Vol. 79, 359-368,
2002.
Keywords:
ultraviolet radiation; exposure; vinyl ester; resins;
damage; atomic force microscopy; infrared spectroscopy;
x-ray photoelectron spectroscopy; integrating sphere;
degradation; FT-IR
Abstract:
The increased use of fiber-reinforced vinyl ester
composites in outdoor applications has led to questions
concerning the environmental
durability of these materials, particularly as related
to UV exposure. In this work, artificial ultraviolet
(UV) degradation was carried out on neat vinyl ester
matrix specimens using an integrating sphere-based UV
exposure chamber. Significant changes were observed in
the bulkmechanical properties, surface chemistry, and
surface morphology after 1000 and 4000 h of exposure. A
transition from slightly ductile to brittle behavior was
observed along with a decrease of up to 40% in average
strain to failure and a decrease of up to 60% in the
average specific toughness after exposure. Changes in
the hardness and modulus of the surface after exposure
were studied by using an atomic force microscopy (AFM)
nanoindentation technique. A significant increase in the
apparent hardness of the exposed surface was accompanied
by an increase in the apparent modulus of the
near-surface region. Morphological changes, including an
increase in both the number and size of surface defects
on the exposed surface were observed using optical
microscopy and tapping-mode AFM. Chemical changes in the
exposed surfaces were also observed using Fourier
transform infrared- attenuated total reflectance
(FTIR-ATR) spectroscopy and x-ray photoelectron
spectroscopy (XPS).
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899