Contamination of brake fluid by power steering fluid.
Analysis of a contaminated brake fluid revealed the contaminant to be power steering fluid. The sample received at the laboratory presented two immiscible phases, which were both organic. Both fluids were analyzed by GC-MS and compared with a library of known automotive fluids. The bottom layer (brake fluid) consisted of glycols while the top layer (power steering fluid) consisted of aliphatics ranging from C16 to C25+. An interesting phenomenon of diffusion of some of the glycols from the brake fluid phase into the power steering fluid phase was observed and needs to be taken into consideration in the interpretation of the results.
Microbial growth in brake fluids
Abstract Bacterial and fungal growths in brake fluids were studied. Bacteria isolated from used Ate and Allied brake fluids were: Bacillus sp., Actinomyces sp., Micrococcus sp., Serratia sp., Citrobacter sp., Pseudomonas sp., Nocardia sp., Acinetobacter sp., Aeromonas sp. and Alcaligenes sp. Bacteria isolated from unused brake fluids were Bacillus sp., Micrococcus sp., Serratia sp., Citrobacter sp. and Actinomyces sp. There were no fungi isolated from unused brake fluids. Fungi found in used brake fluid were Mucor sp., Geotrichum sp., Aspergillus sp., Cladosporium sp. and Penicillium sp. Average counts for total viable microorganisms in used brake fluid ranged from 1.02 × 105 to 2.16 × 108 cfu ml−1, its average optical density ranged from 0.12 to 0.76, its average pH ranged from 4.3 to 7.8 and its average viscosity ranged from 5.39 to 10.29 cSt while for the unused brake fluid, average counts for viable microbial cells ranged from 1.1 × 105 to 6.0 × 105 cfu ml−1, average values for optical density ranged from 0.07 to 0.36, its average values for pH ranged from 6.5 to 8.4 and its average viscosity values ranged from 12.92 to 14.02 cSt. The use of brake fluid according to the manufacturer’s guide should not be ignored and regulatory agencies should also ensure that the braking system of every vehicle is in order.
Characterisation of rubbers, rubber contact traces and tyre prints by fluorescence spectroscopy
Fluorescent contact traces are transferred from many rubber articles, and may be characterised, after extraction, by synchronously excited fluorescence emission spectroscopy. The fluorescence is due mainly to extender and process oils, to antioxidants, and to polynuclear aromatic hydrocarbons. Variation in these components in tyre treads, caused by variation in manufacture and wear, enables tread rubbers, and their prints, to be efficiently distinguished from one another. Fluorescent tyre print formation is controlled by the nature of the surface, and by contact time and pressure. Some of the fluorescent material solvent-extracted from such prints is present initially as non-fluorescent particles of rubber. Tyre sidewall rubbers are distinguished from tread rubbers by differences in the extraneous polynuclear aromatic hydrocarbon emissions and, in the case of radial tyres, principally by differences in extender oil emissions. The techniques described are also applied to traces left by footwear and by erasers, to the detection of mineral oil in failed brake seals, and can be generally applied in the comparative examination of rubbers.