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Longevity
The most damaging effect of natural weathering is imparted
by UV radiation. The vast majority of materials on earth,
including human skin, is degraded by UV exposure over time.
Symptoms in conventional coatings include chalking, loss of
gloss, discoloration, embrittlement, peeling and actual loss
of film thickness. In North America it has been found that
conventional coatings can lose between 13 to 25 microns (0.5
to 1.0 mils) of film thickness per year due to UV exposure.
UV radiation so readily degrades most earthly materials
because of the energy it supplies. UV light in its various
forms will supply to materials 398 kJ per mole of material.
A mole, in chemistry, is simply 6.023 x 1023 atoms or molecules
of a given substance.
Coatings, whether they are conventional epoxies, alkyds,
polyurethanes, etc., or Si-COAT, are all made up of atoms
linked to other atoms. When we say that UV radiation degrades
a coating, we are saying that UV light is supplying sufficient
energy to the coating to break the bond between the atoms.
In conventional coatings, the energy required to break the
bonds in the resin/polymer can range from 300 to 360 kJ per
mole. The 398 kJ per mole supplied by UV light is more than
sufficient to break the coating apart over time.
In the case of Si-COAT, however, the energy required to
break apart the bonds in the polymer is 461 kJ per mole. Clearly,
UV light cannot provide sufficient energy to break down Si-COAT.
The result is a coating that far outlasts conventional coatings,
even in severe environments.
One way to observe the degradation of a coating under UV
exposure is by its gloss retention. If UV radiation will damage
a coating, the coating will inevitably experience loss of
gloss as the bonds within the resin/polymer are broken. By
virtue of its gloss retention as illustrated in the graph
below, Si-COAT distinctly outperforms conventional coatings
under extended UV exposure.
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