Release from Composites by Mechanical and Thermal Treatment - Safety of Nanomaterials along Their Lifecycle - page 254

velocities between sanding paper and sample were 0.5 and 1.8 m/s, and the contact
pressure was approximately 12,500 Pa. The test objects were epoxy resin and PA
disks, the latter without and with 4 mass% nanoSiO 2 . The released particles dur-
ing the sanding process were measured with FMPS and APS. Additionally, ESP
and contact samples were taken by carbonaceous adhesive pads for offline scanning
electron microscope (SEM) analysis.
The ratios of the geometric mean concentration measured during the sanding
process to the concentration measured in the background (P/B ratio) are shown in
Table 12.2. Epoxy resin emitted significantly more particles (especially coarse par-
ticles) than PA. Furthermore, it was found that during the sanding process of PA
the nanoparticle number concentration measured with the FMPS (with about 90%
particles <100 nm) was negligible compared with the background concentration with
a mean P/B ratio of 1.11 for PA with nanoSiO 2 . The micrometer-ranged particles
(measured with APS) showed in almost all cases very high P/B ratios indicating a
high particle release in this size range.
Table 12.3 summarizes the test parameters and results of the selected test meth-
ods. The presented studies show that in most cases enclosed boxes were employed to
(a) reduce the background aerosol concentration and (b) to ensure the safety of the
operators. Additionally, it is evident that particle samples had to be taken to find out
if the nanofillers or other nanoscale particles were released.
A comparison of all sanding test methods employed shows a general trend to
testing in enclosures with possibilities to adjust and define parameters and test con-
ditions. Still, some of the published test setups do not allow easily for quantitative
release measurements and standardization. Anyhow, basic conditions for harmonized

TABLE 12.2
Results of the Sanding Tests from IUTA

Grit
Level

P/B FMPS
5-550 nm Diameter

P/B APS
700 nm-5 µm Diameter Test Object Speed, m/s

Epoxy resin 80 0.5 9.8 772.1

Epoxy resin 80 1.8 17.4 507.8

Epoxy resin 320 0.5 3.3 97.3

Epoxy resin 320 1.8 12.7 131.5

PA neat 80 0.5 1.1 59.8

PA with SiO 2 80 0.5 1.09 12.0

PA neat 80 1.8 5.7 45.3

PA with SiO 2 80 1.8 1.32 61.4

PA neat 320 0.5 1.4 15.1

PA with SiO 2 320 0.5 0.96 2.9

PA neat 320 1.8 4.9 20.1

PA with SiO 2 320 1.8 1.07 10.9

Note: P/B is the ratio of sanding process/background.
Abbreviations:

APS, aerodynamic particle sizer; FMPS, fast mobility particle sizer; PA, polyamide.