Page 453 - Handbook of Materials Failure Analysis

3 Results 451

Table 17.1 Pyrolysis Products of the Rubber Membrane with Coating
at 550 and 700 °C
Peak Retention Pyrolysis Product Pyrolyzed Material
Time
(RT) (min)
1 8.60 1-Butene/1,3-butadiene SBR
2 10.37 Benzene SBR, phenol resin
3 12.02 Toluene SBR, phenol resin
4 14.14 Styrene SBR
5 14.83 Ethenyloxybenzene Additive
6 15.40 Phenol Phenol resin
7 15.87 Benzofuran PET
8 16.64 o-Cresol Phenol resin
9 16.99 p-Cresol Phenol resin
10 17.13 Acetophenone PET
11 19.60 Naphthalene SBR
12 19.88 Phenoxyethanol (Dowanol EP) Additive
13 20.40 Benzothiazole Additive
14 21.73 2-Methylbenzothiazole Additive
15 24.74 2-Phenoxyethyl acrylate Additive
16 25.03 1-Pentadecene Mineral oil
17 26.96 1-Hexadecene Mineral oil
18 28.95 1-Heptadecene Mineral oil
19 30.62 1-Octadecene Mineral oil
20 32.0-45.0 Heavy n-alkanes Mineral oil

resin coatings. It was assumed that ethenyloxybenzene (RT¼14.83 min) was generated
from the additive. Additionally, by pyrolyzing the lacquer coating from the defective
surface of the rubber membrane, a mixture of straight-chain aliphatic hydrocarbons
corresponding to heavy n-alkanes and α-alkenes (Figures 17.4 and 17.5; Table 17.1)
was detected. The detected compounds suggest the presence of a mineral oil (heavy
n-alkanes) on the defective surface of the rubber membrane. The identified α-alkenes
(Figure 17.5, peaks 16-19) are known as pyrolysis products of mineral oil [2]. Based
on the obtained results, it was found that the cause of the defect in paint work on the
surface of a rubber membrane from the automotive pressure vessel was the mineral
oil.The obtained analytical results were then used for troubleshooting withthe customer.

3.1.2 Case 2: Identification of the composition of claimed motor
vehicle brake fluid
Motor vehicle brake fluids are used to transfer energy to the actuating mechanism in
the hydraulic drive of the brake assembly of a car and to remove heat from the brake
discs [6]. The main requirements for brake fluids are high operation temperatures,