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Analysis of Fuels, Tyre Surfaces and Tyre Inflation Gases at the race-track with a Mobile Gas Chromatograph System "mobilab"
by Karl-Heinz Stegner and Eugen Klaus


1. Mobile Laboratory


At the request of the DMSB e.V, Stegner & Klaus Engineering have developed and produced a mobile laboratory for analysis and examination of fuels, particularly racing fuels, tyre inflation gases as well as rubber samples from tyre surfaces of racing tyres.

This mobile laboratory consists of the following equipment:

> Gas chromatograph (GC for the examination of the rubber and the fuel)
> Electronic injector (permits a direct examination of rubber in the GC)
> Automatic sampler (for an automatic injection of fuel into the GC)
> Hydrogen generator (for the production of the H2 to run the equipment)
> Hydrogen sensor (for the supervision of hydrogen leakages of the stove in the GC)
> Zero air generator (for production of pure air to run the equipment)
> Air compressor (for operation of the GC system)
> Printer (for documentation)
> Mobile computer (for the evaluation of the analysis)

With this laboratory an analysis and examination of fuels, racing tyre surfaces as well as of tyre inflation gases is possible while still at the circuit. The laboratory is designed for transportation with motor vehicles or by airfreight (under consideration of compliance with the dangerous goods regulations). The complete equipment is installed in four Flight-Cases (55 cm, 60 cm, 65 cm, B, H, T, weight approx. 230 kg), which can be unpacked into two columns to form the laboratory. With this equipment, the analysis described above can be performed in almost any location. (See picture)

Picture 1: Mobile laboratory arranged into two columns
Picture 1: Mobile laboratory arranged into two columns

2. Fuel Analysis


2.1 Fuel Sampling
A reference sample is taken from the specified fuel. At a suitable place the fuel from the racing vehicle is directly taken from the fuel system by a tube and put into a fuel-tight locking container. Three (3) samples are taken. One sample is examined on the spot, a second one is given to the organizer and the third sample stays with the racing team.
2.2 Test Method
The reference sample and the samples out of the racing vehicle are examined in the gas chromatograph. In the GC the fuel mixture is separated into its individual components and each component is shown in a chromatogram. The evaluation is made by comparing the reference sample to the samples from the racing vehicle like a finger print. Changes or contaminations of the fuel are shown in the different chromatograms.

Picture 2: comparing the reference sample to the fuel sample from the racing car
Picture 2: comparing the reference sample to the fuel sample from the racing car

3. Analysis of Tyre Compound


3.1 Method of Taking Tyre Samples
S & K Engineering have developed a method of testing the rubber of racing tyres, which permits to take a sample from the racing tyre or the tyre surface without damaging either the tyre or the tyre surface. The sample is taken with a special instrument.
The instrument enables you to draw strips from the tyre surface which are approx. 1-2 mm wide, 0.3 mm thin and approx. 25-30 mm long. In sequence each single strip is examined and presented in a gas chromatogram to discover any eventual chemical treatment, i.e. whether softeners have been used.
To exclude possible faults, the samples should be taken at three different parts of the tyre surface. From each of these locations, three strips have to be taken and distributed to the team, the organizer and the laboratory. These samples are kept in sealed metal boxes (e.g. the same type of containers as for the fuel).
3.2 Methods to Analyse Tyres
S & K Engineering, i.e. Dipl.Ing.(University) Karl-Heinz Stegner and Dipl.Ing.(FH) Eugen Klaus in cooperation with diploma chemist Dr. Harald Wetzel have developed and improved two methods, which permit the analysis of solid rubber samples from tyre surfaces in a summary proceeding (direct analysis in an injector in the GC) and in a further procedure, taking a little more time (extraction). Both methods are carried out with the help of the available GC-Systems equipment.
The direct analysis of the tyre sample in the GC shows the result within 10 min after the beginning of the test. The rubber sample (or a part of put into a glass liner in front of the corresponding separating column within the GC. It is then subjected to a temperature program where the sample is “express”-heated in the electronic Injector and the gases escaping from the rubber sample create the gas chromatogram.
To analyse according to the extraction method it takes some more time, i.e. the rubber sample is put into a vessel, (e.g. a bottle) with an extraction liquid in it, for approx. one hour. Afterwards the extraction liquid is filled into the injector and analysed. As this method needs more time and material, it is used at the circuit only in extraordinary situations. It is useful as an alternative method to control the direct analysis and to push ahead further methods of development and confirm existing results.
3.3 Results of the Tyre Analysis
3.3.1 Detection of Softeners in Treatments (common treatment liquids)
Basic material for the analysis was a brand-new racing tyre and a racing tyre already being used in competition. Treatment liquids, e.g. “XXX-LAP”, which are offered on the international market, were tried out. First of all original “XXX-LAP” was analysed in the GC (mixed with a neutral solvent).

Picture 3: XXX-LAP means 2125 with softener, the Retention time is 9.2 minutes.
Picture 3: XXX-LAP means 2125 with softener, the Retention time is 9.2 minutes.

Picture 4: XXX-LAP means 7000 with softener, the Retention time is 9.2 minutes.
Picture 4: XXX-LAP means 7000 with softener, the Retention time is 9.2 minutes.

Picture 5: XXX-LAP means 6000 with softener, the Retention time is 9.2 minutes.
Picture 5: XXX-LAP means 6000 with softener, the Retention time is 9.2 minutes.

Picture 6: XXX-LAP means 7032 with softener, the Retention time is 9.2 minutes.
Picture 6: XXX-LAP means 7032 with softener, the Retention time is 9.2 minutes.

Picture 7: Tyre cleaner 7050 without softeners
Picture 7: Tyre cleaner 7050 without softeners

The analysis of the different treatment liquids (softeners) has shown that all liquids contain the same softener, (except XXX-CLEANER 7050). The only difference is the quantity (concentration) of the softener.
3.3.2 Identification of Phthalate
To identify, which of the softeners is contained in the liquids offered on the market, different well-known softeners of the same type had to be analysed. The result was the identification of the softener contained in the above-mentioned treatment liquids: It is “Bis-(2-ethylhexyl) phthalate”.

Picture 8: Identification of Phthalate.
Picture 8: Identification of Phthalate.

3.3.3. Identification of softeners in treated tyres
After the treatment liquids had been analysed, and the particular softener was identified, the different tyres had to be examined. Both, surfaces - of brand-new and already used tyres - were divided in sections and treated with different liquids Furthermore some sectors were treated with oil, gasoline and coolant that are likely to be found on a circuit or on a road.

Picture 9: tyre divided in sections.
Picture 9: tyre divided in sections.

After 15 minutes one sample had been taken from each section of the tyre and analysed. By means of both developed methods the analysis was carried out (extraction and direct analysis of solid substances in the GC). The results of the two different methods correlate perfectly.

Picture 10: comparison tyre untreated to tyre treated with XXX-LAP 2125 (extraction method). The XXX-LAP softener was clearly identified.
Picture 10: comparison tyre untreated to tyre treated with XXX-LAP 2125 (extraction method). The XXX-LAP softener was clearly identified.

Picture 11: comparison tyre untreated to tyre treated with XXX-LAP 7000 (extraction method).
Picture 11: comparison tyre untreated to tyre treated with XXX-LAP 7000 (extraction method).

Picture 12: comparison tyre untreated to tyre treated with XXX-LAP 6000 (extraction method).
Picture 12: comparison tyre untreated to tyre treated with XXX-LAP 6000 (extraction method).

Picture 13: comparison tyre untreated to tyre treated with XXX-LAP 7032 (extraction method).
Picture 13: comparison tyre untreated to tyre treated with XXX-LAP 7032 (extraction method).

Picture 14: comparison tyre untreated to tyre treated (direct analysis in the injector).
Picture 14: comparison tyre untreated to tyre treated (direct analysis in the injector).

Direct analysis (in the electronic Injector) and the extraction method have both shown equivalent results.
3.3.4. Review how deep softeners get into the tyre surface
It was also considered to be interesting to investigate how far the treatment liquids penetrate into the tyre. To find that out, second samples were taken at the same spot where the first sample had been taken, i.e. the second samples are of a deeper layer of the surface (approx. 0.6 – 1.0 mm). The analysis confirmed that the liquids can hardly be found in these lower layers, i.e. the softening liquids don’t get deeper than 0.3 to 0.6 mm into the surface of the tyre. There are no grounds for supposing, that Air Filling Gases for tyres (e.g. spray XXX-LAP) offer the opportunity of treating the tyre from its inner to outer layers by diffusion, and that any advantage at the surface or the tread of the tyre can be achieved by such methods.

Picture 15: comparison of the lower layer to the upper layer, the softener from the lower layer can be hardly recognized
Picture 15: comparison of the lower layer to the upper layer, the softener from the lower layer can be hardly recognized

3.3.5. How long/short are the softeners effective?
Next item was the question, for how long softeners can be detected. The same samples were examined after 2 hours, 2 weeks and 2 months after they had been treated with softeners. At all available and analysed samples the softener of the type XXX-LAP has been recognized without doubt, i.e. it is certain that if a tyre has ever been treated with a softener, the softener can be detected on the surface (depth up to 0.6 mm) unless the surface is worn completely away.
Even a racing tyre (e.g. DTM) heated up again and again on operating temperature shows the same results, i.e. it is always possible to recognize that a tyre has been treated with softeners even after it has been heated up several times to its operating temperature.

Picture 16: examination two days after a treatment, softener detectable
Picture 16: examination two days after a treatment, softener detectable

Picture 17: examination two weeks after a treatment, softener detectable,
Picture 17: examination two weeks after a treatment, softener detectable,

Picture 18: examination two months after a treatment, softener clearly detectable (direct method)
Picture 18: examination two months after a treatment, softener clearly detectable (direct method)

3.3.6. Influence of contaminants from the road
A further test was performed to find out whether oil, fuel, cooling water or other things found on the road or track surface, could possibly influence the results of the tyre analysis. An extensive programme of tests showed conclusively that the detection of the softeners is not affected in any way by the contaminants previously mentioned, since the retention time of those substances differs markedly from the retention time of the softeners (liquids). The chromatograms show peaks either in lower areas (i.e. for fuel) or at the higher end of the data registration (i.e. for oil, cooling water etc.) or they are so small, when compared to the detectable softeners, to be disregarded.

Picture 19: comparison tyre untreated to tyres treated with fuel (gasoline).
Picture 19: comparison tyre untreated to tyres treated with fuel (gasoline).

Picture 20: comparison analysis of a neutral tyre surface to a tyre surface that had been in contact with oil
Picture 20: comparison analysis of a neutral tyre surface to a tyre surface that had been in contact with oil

4. Tyre Inflation Gases


The available GC system and its equipment enable one to detect whether there are any type of solvents in the gas used to inflate a tyre.
The sampling can be carried out with a gas mouse. The gas can be analysed by a direct injection with a gastight needle into the GC. The method is very similar to the method used to analyse the fuel. Up to now there has not been an opportunity to perform tests to develop a methodical procedure, because the necessary liquid is not yet available. If the liquid contains a similar softener to that of the liquids of the type “XXX – Lap” a test result might be achievable by examining the inside surface of the tyre (perhaps by a wiping test without damaging the tyre).

5. Summary

According to the methods developed by us - including a substantial quantity of practical analysis-, it is possible to detect any addition or pollution in the fuel, as well as to reveal any type of softeners present on the surface of the tyres (XXX - Lap) or in the tyre inflation gas while still at the racing circuit.
The sampling to detect whether the surface of a racing tyre has been treated chemically or not, has to be obligatory before the beginning of a race, qualifying or free practice, since otherwise a treatment can be spoilt by abrasion and no certain proof can be presented.
The analysis and result of one single sample is available within approx. 15 min after receipt in the laboratory. Pollutions like oil, gasoline (fuel) or cooling water do not influence the analysis in any way, i.e. arguments of teams are not effective, that the vehicle concerned had driven over oil, fuel or other contaminants,. The method permits both, an analysis of brand new as well as used (driven) tyres.