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The
advantage of using synthetic resins in modern art and conservation paints is the
higher performance and durability of these materials over traditional natural
media. However, incorporating
pigments into the resin can affect its properties, either increasing its
resistance to aging by screening harmful radiation, or decreasing its stability
through sensitizing photochemical reactions.
We have examined the effect of adding white pigments and extenders on the
photochemical degradation of poly(n-butyl methacrylate), a polymer that has seen
use as a conservation coating and as a medium for retouching paints.
This particular resin has been found to undergo predominantly
cross-linking chemistry during exposure to near-ultraviolet light, slowly
becoming insoluble. The
research focus is to determine the effect of three different types of white
pigment on the solvent-based synthetic resin paints.
The
UV-absorbing pigments slowed the overall degradation rate by decreasing the
intensity of light reaching the polymer. While
the photochemically-active titanium and zinc pigments did not alter the
propensity for crosslinking, these chalking pigments did cause oxidative
reactions, which created volatile products that left the paint films.
The extender pigments accelerated the resin degradation by a factor of
two due to the increased scattering and diffusing of the light within the film. For more information: |