Mechanisms of Aging and Release from Weathered Nanocomposites - Safety of Nanomaterials along Their Lifecycle - page 329

Because most common polymers are susceptible to photodegradation under
weathering environments, even those containing UV stabilizers, these nanofiller
release models are equally applicable to other polymers. Further, matrix degrada-
tion will cause extensive oxidation, chain scission, and crosslinking of the polymer
chains, which results in an increase in brittleness, loss of mechanical properties,
and cracking of the polymer nanocomposites. This loss of mechanical integrity will
promote nanofiller migration and release. However, appropriate measures, such as
adding UV stabilizers to the formulation, are routine praxis in polymers for outdoor
applications. Addition of UV stabilizers or protective coatings delays the nanofiller
release to the disposal phase, where landfilling or waste combustion could be emis-
sion sources, and are discussed in Chapters 12 and 15. During the use phase, release
of polydisperse fragments including nanofillers occurs at nonzero rates, but limited
to micrometer-thin surface layers, with emerging mechanistic understanding. For
environmental mass flow estimates, the use phase is hence a relatively small source
compared to production, recycling, and disposal phases.
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