Mechanisms of Aging and Release from Weathered Nanocomposites - Safety of Nanomaterials along Their Lifecycle - page 316

Inductively coupled plasma mass//
optical emission spectrometry
(ICP/OES)//(ICP/MS)
Scanning electron microscopy (SEM)
Transmission electron microscopy
(TEM)

Optical properties Surface morphology

Transmission electron
microscopy (TEM)
Scanning electron microscopy
(SEM)
Atomic force microscopy
(AFM)
Laser scanning confocal
microscopy (LSCM)

Gloss loss

Yellowing
Cracking
Discoloration

Size classification by analytical
ultracentrifugation - refractive index
(AUC-RI) or field-flow-fractionation
(FFF-RI/FFF-ICPMS)

Tensile testing
Dynamic mechanical analysis
(DMA)
Nanoindentation

Physical
properties

Nano-
particle
release

Mechanical
properties

Characterization
of weathering
and release

Material
loss

Molecular weight

Thermogravimetric
analysis (TGA)
Analytical balance

Gel permeation chromatography
(GPC/SEC)
Viscosity

Chemical
properties

Radicals, ions

Functional changes

Electron spin resonance (ESR)
Chemiluminescence

Fourier-transform infrared spectroscopy
(FTIR)
UV visible spectroscopy
Photophosphorescence
Chemiluminescence
X-ray photoelectron spectroscopy (XPS)
Secondary ion mass spectroscopy (SIMS)
Nuclear magnetic resonance spectroscopy
(NMR)
Contact angle

Degraded product

Gas chromatography (GC)
Gas chromatography-mass
spectrometry (GC/MS)

Matrix-assisted laser desorption/
ionization (MALDI-TOF)

FIGURE 14.1 Techniques for characterizing weathering of polymer nanocomposites and
nanofiller release.

that are being or potentially used in polymer nanocomposites for a variety of applica-
tions. MWCNTs are technically suitable nanofillers for enhancing the performance
of polymers where high strength, exceptional electrical conductivity, light weight,
and high aspect ratio can distinguish them from other nanofillers (McNally and
Pötschke 2011; Ma et al. 2010), although only niche applications tolerate today's
high prices. Degradation behavior of polymer-MWCNT nanocomposites subjected
to UV radiation has been reported. Measured release from polymer-MWCNT and
release probabilities extrapolated from degradation of the pure polymer have been
reviewed (Kingston et al. 2013), identifying matrix degradation as the only relevant
release scenario. An early study by Najafi and Shin (2005) found that the degrada-
tion rate of poly(methyl methacrylate)/MWCNT nanocomposite irradiated by UV
in ozone is substantially reduced as the loading of MWCNTs increased from 0.02%