VW PV 3935 Plastics and Elastomers - Py-GC/MS, TD/Py-GC/MS, Heart-Cut, EGA

The standard "VW PV 3935 Plastics and elastomers - Py-GC/MS, TD/Py-GC/MS, Heart-Cut, EGA" developed by the Volkswagen automobile company describes a procedure for the analysis of polymers by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). This analytical method allows the evaluation of thermoplastics, elastomers, thermoplastic elastomers and thermoset materials (duromers), as well as any organic material (sediment) and organic additives.

A major advantage of this method is that it enables analysis of even insoluble, vulcanized materials, such as paints, adhesives and coatings, which is not possible with other chemical methods for structure determination. It also does not require complex sample preparation. Information is obtained on the materials and organic additives, among other things anti-aging agents, plasticizers, antistatic agents and processing agents. In addition, comparative structural changes resulting from aging processes or changes in the materials can be determined.

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

For the purposes of this standard,

• Autotuning is the self-calibration of the mass spectrometry detector by means of a special standard substance (PFTBA).
• A chromatogram is a diagram showing detector intensity versus retention time.
• Gas chromatograph is a device used to separate vaporized and gaseous substances. The main components are injector, column, detector and oven.
• The mass spectrometer is the universal detector in gas chromatography. It ionizes substances in an ion source in vacuum. In the analyzer, the ions are separated and recorded in an electromagnetic field that varies depending on their mass/charge ratio, for example a quadrupole field.
• A pyrolyzer is a device used for the evaporation and thermal decomposition of predominantly organic compounds in inert gas atmospheres.
• The retention index is for instrument-independent standardization of retention times of unknown analytes based on the relationship between carbon content and retention time (Kovats index).
• Retention time is the time it takes for a substance to be detected in a gas chromatography system.
• Splitting mode is a method of splitting the gas flow to be analyzed.

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

• Pyrolysis is performed first, in which the solid sample is broken into small pieces under inert conditions, thus making it available 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.

The stainless steel pan containing the samples is transported to the pyrolysis oven via the optional automatic sampler. The resulting gaseous substances are washed with an inert gas flow (e.g. helium or nitrogen) via the injector into the gas chromatography column located in a temperature-programmable oven.

At the beginning of the column, substances from a previous desorption process are optionally focused with the help of a cryopump. Separation occurs in 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 by an electron beam. The charged fragments are selected and then detected by a quadrupole analyzer. Data recording and control of all components are carried out by a computer.

Meanwhile, different analytical methods can be performed:

• Advanced gas analysis: This method uses a short, deactivated gas chromatography column with no stationary phase. The degassing agents are directed directly to the detector without gas-chromatic separation. A thermogram, similar to thermogravimetric analysis, is produced with an average mass spectrum across all masses.
• Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS): The pan is moved to the oven preheated to the pyrolysis temperature, where the sample is instantly pyrolyzed and the produced fragments are carried to the gas chromatography column.
• Thermal desorption pyrolysis-gas chromatography/mass spectrometry (TD/Py-GC/MS) (default method): This technique provides information about volatile components and the polymer simultaneously. To do this, in the first step, the sample is heated over a temperature range to degas volatile components (thermal desorption). These volatile components are captured and analyzed by GC/MS. In the second step, the remaining sample is pyrolyzed and the polymer composition is determined.
• Multiple temperature range analysis (Heart-Cut): This method allows a multi-component system to be analyzed. With the help of this method, multiple temperature ranges can be tested one after another to determine the composition of the components in the temperature range of interest.

Among the numerous testing, measurement, analysis and evaluation studies that our organization has carried out for businesses in various sectors, it also provides testing services defined in the “VW PV 3935 Plastics and elastomers - Py-GC/MS, TD/Py-GC/MS, Heart-Cut, EGA” standard with its trained and expert staff and advanced technological equipment.