Mechanisms of Aging and Release from Weathered Nanocomposites - Safety of Nanomaterials along Their Lifecycle - page 328

UV

Polymer/MWCNTs
nanocomposites before UV
exposure

Polymer/nanoSiO 2
nanocomposite before UV
exposure

UV

UV

Under UV radiation, the
polymer layer near the
surface photodegrades and
is removed

As the polymer layer near the
surface undergoes
photodegradation and is
removed, → SiO 2 nanoparticles
are increasingly accumulated
on the surface.

UV

UV

Æ MWCNTs are increasingly
accumulated on the surface,

UV

At critical concentration and in
liquids to lower adhesive forces
→ fragments incl. SiO 2
nanoparticles release
(rain, condensed water, wind,
shear, induce increased release
reates)

UV

UV Æ and form a dense, collapsed

network held by van-der-Waals
forces that require strong shear
to induce release.

(a) (b)

FIGURE 14.7 Conceptual models for (a) surface accumulation and release of SiO 2 nanoparticles from epoxy/nanosilica composites. (b) The formation
of a dense collapsed MWCNT network on the nanocomposite surface during exposure to UV radiation.