Headspace Assay of Polymers used in the Automotive Industry with Teledyne Tekmar HT3 Dynamic Headspace Instrument
Synthetic and natural materials are used extensively by the motor vehicle industry to provide customers appealing and safe vehicle interiors. The materials used in all aspects of vehicles interior, range from cloth and leather seats to the plastics used in the dashboards. The manufacturing process used for these materials typically include volatile (VOC) and semi volatile organic compound (SVOC) which are released into the interior of vehicles.
These compounds give the vehicles that new smell but can also lead to fog on the interior glass surfaces of the car and health issues with the occupants. Vehicle manufactures and government regulatory agencies are investigating limits relating to the VOC and SVOC and their allowable concentrations in the interior of vehicles.
The Japanese Automotive Manufactures Association (JAMA) and the voluntary program for the European Automotive Industry, VDA, whose limits are defined by TÜVRheinland are two of these agencies. Their limits are listed in Table 1.
The typical method of collecting VOC and SVOC from the vehicle cabin is to flow air through the cabin and collect these compounds on thermal desorption tubes. The tubes are then tested with a thermal desorption instrument. Thermal desorption is well suited for the final testing of the vehicle interiors. However, it has limitations for use by the manufactures of products that go into the vehicles interior prior to final assembly.
One method from the VDA for testing these materials, Method VDA-278, uses thermal desorption. It instructs the parts suppliers of the vehicle interior materials how to test their products to meet the vehicle manufactures requirements for VOC and SVOC.
Thermal desorption has some known disadvantages listed in VDA 278. Section 4.4.1, Trimming and Weighing of Samples for Thermal Desorption Tubes indicates that the sample must be reduced to fit into the thermal desorption tube, which has an internal diameter of 4mm. Section 6, Possible Errors, Known Problems, also indicates that heating of the sample that may be generated during the mechanical reduction can drive off VOC’s creating false negative results and should be avoided.