VW PV 3935 Automotive - Test Standard for Plastics and Elastomers

The VW PV 3935 test standard describes the analysis of polymers by means of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). This analytical method enables the evaluation of thermoplastics, elastomers, thermoplastic elastomers and thermoset materials (duromers), as well as any organic materials (depositions) and organic additives.

A great advantage of this method is that it makes it possible to analyze even insoluble, cured materials, such as paints, adhesives and coatings, which are not possible with other chemical methods for structure determination. It also does not require complex sample preparation. Among other things, information is obtained on materials and organic additives, as well as anti-aging agents, plasticizers, anti-static agents and treatment agents. In addition, comparative structural changes due to aging processes or changes in materials can be determined.

Both a qualitative analysis and a quantitative analysis are possible after prior calibration.

The Py-GC/MS method combines three different processes:

Pyrolysis, which is performed first, in which the solid sample is broken up into small fragments under inert conditions, thus making it suitable for gas chromatography.

The second step is the separation of the obtained fractions by gas chromatography.

The third step involves the detection and characterization of these fragments by mass spectrometry.

Shows a schematic representation of a Py-GC/MS device with individual components. The stainless steel pan with the samples is transported to the pyrolysis furnace by the optional automatic sampling device.

The resulting gaseous substances are flowed via an injector with a stream of inert gas (eg helium or nitrogen) onto a gas chromatography column in a temperature programmable oven. At the start of the column, optionally substances from a previous desorption process are frozen with the aid of a cryopump. Separation occurs on the column due to different boiling points and interactions with the column coating.

At the end of the gas chromatography column, the substances are transported to the mass spectrometer, where they are fragmented and ionized with the aid of an electron beam. The loaded parts are selected and then detected by a quadrupole analyzer. Data recording and control of all components are done with the help of computer.

For statistical quality verification, each sample needs to be analyzed multiple times. The required number of sample cups is provided in one cup holder.

Solutions of internal standards (2.5 µl of benzo(a)pyrene-d₁₂ in cyclohexane; 100 ng/µl for desorption and 2.5 µl of styrene-d₈ in methyl ethyl cenote; 100 ng/µl for pyrolysis) are sprayed into it. each pan of microliters is evaporated by means of a spray device and the solvent is evaporated at room temperature until it reaches a constant weight.

If a different internal standard is used, the selection should ensure that only one peak will result in the mass spectrum for both desorption and pyrolysis.

A homogeneous piece should be prepared from the sample to be examined and the mass should be determined with an accuracy of ± 1 µg. This sample mass is chosen such that the pure polymer component minus all non-pyrolysable components (150 ± 10) µg. If this sample amount is not sufficient, the split ratio can be adapted accordingly.

For properties and conditions of the sample, such as water content, the same restrictions apply to Py-GC/MS analyzes as for liquid injection GC/MS analyses. If a cryopump is used, it must be ensured that sufficient liquid nitrogen is available.

Our EUROLAB test laboratory complies with ISO/IEC 17020 General requirements for the competence of testing and calibration laboratories to help ensure accuracy and precision in performing tests, obtaining data and reporting results. EUROLAB comes with environmental cycle endurance tests, detailed test reports, images of labels before and after testing, and all test data for review and analysis.