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Abstract
<p class="first" id="P1">Nano-fillers are increasingly incorporated into polymeric
materials to improve the
mechanical, barrier or other matrix properties of nanocomposites used for consumer
and industrial applications. However, over the life cycle, these nanocomposites could
degrade due to exposure to environmental conditions, resulting in the release of embedded
nanomaterials from the polymer matrix into the environment. This paper presents a
rigorous study on the degradation and the release of nanomaterials from food packaging
composites. Films of nano-clay-loaded low-density polyethylene (LDPE) composite for
food packaging applications were prepared with the spherilene technology and exposed
to accelerated weathering of ultraviolet (UV) irradiation or low concentration of
ozone at 40 °C. The changes in the structural, surface morphology, chemical and physical
properties of the films during accelerated weathering were investigated. Qualitative
and quantitative changes in properties of pristine and aged materials and the release
of nano-clay proceeded slowly until 130 hr irradiation and then accelerated afterward
resulting complete degradation. Although nano-clay increased the stability of LDPE
and improved thermal and barrier properties, they accelerated the UV oxidation of
LDPE. With increasing exposure to UV, the surface roughness, chemiluminescence index,
and carbonyl index of the samples increased while decreasing the intensity of the
wide-angle X-ray diffraction pattern. Nano-clay particles with sizes ranging from
2–8 nm were released from UV and ozone weathered composite. The concentrations of
released nanoparticles increased with an increase in aging time. Various toxicity
tests, including reactive oxygen species generation and cell activity/viability were
also performed on the released nano-clay and clay polymer. The released nano-clays
basically did not show toxicity. Our combined results demonstrated the degradation
properties of nano-clay particle-embedded LDPE composites toxicity of released nano-clay
particles to A594 adenocarcinomic human alveolar basal epithelial cells was observed,
which will help with future risk based-formulations of exposure.
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