Page 449 - Handbook of Materials Failure Analysis

3 Results 447

kept at 230 °C. The ionization occurred with a kinetic energy of the impacting elec-
trons of 70 eV. The quadrupole temperature was 150 °C. Mass spectra and recon-
structed chromatograms (TIC) were obtained by automatic scanning in the mass
range m/z 35-750 u. The solvent delay was 9 min.

3 RESULTS
3.1 APPLICATION OF Py-GC/MS AND SEM IN FAILURE
ANALYSIS IN THE AUTOMOTIVE INDUSTRY
For the failure analysis in motor vehicles, there is often lack of information about the
component itself, such as chemical composition, temperature resistance, possible
contaminants, or mechanical properties. The damage range is usually limited and
not always homogeneous. The SEM allows the exact localization of damage of com-
ponents from engineering and automotive industry. There are often only small
amounts of samples available to clarify the damage, which may be important for rec-
ognizing the cause of damage [2,3]. The increasing use of polymeric materials in the
automotive industry requires sensitive and reliable methods for its analysis. Tradi-
tional analytical techniques used for characterization of polymers/copolymers, such
as thermal analysis and FTIR, have limitations or are not sufficiently sensitive to
demonstrate the change of the structure and the resulting dysfunction of used mate-
rials. A lot of information about dysfunction of automobile parts can be obtained
from the fouling material on the surface of the failed parts. In such cases, the sam-
pling can be made by rubbing the affected surface with the quartz glass wool
followed by the Py-GC/MS of the enriched wool. The other problem could be the
difficulty in the interpretation of pyrograms (Py-GC/MS chromatograms) of com-
plex mixtures or blends because of the large number of decomposition products.
In such cases, an extended analysis is required.
3.1.1 Case 1: Defect work in paint on the surface of a rubber
membrane from the pressure vessel of an automotive integral
accumulator
The goal of the first study was to investigate the cause of defect work in paint on the
surface of a rubber membrane from a pressure vessel (automotive component).
Figure 17.3a and b shows the state of the investigated pressure vessel and a magnified
viewofthedefectlocationontherubbermembranesurface,respectively.Thesamplesof
thelacquercoatingfromthegoodandfromthedefectivesurfaceoftherubbermembrane
werepyrolyzedat550 and 700 °C, respectively followed byGC/MS analysisto identify
their composition. Figures 17.4 and 17.5 show the obtained pyrograms of the samples.
Basedonthedecompositionproducts summarizedinTable 17.1,thesampleswere iden-
tified as a mixture of styrene-butadiene rubber (SBR), phenol resin, poly(ethylene
terephthalate) (PET), and additives. The main feature of the pyrolysis of SBR is
the formation ofbutene/butadiene (RT¼8.60 min), benzene (RT¼10.37 min),toluene
(RT¼12.02 min), styrene (RT¼14.14 min), and naphthalene (RT¼19.60 min)