Normally the appropriate identifier is marked on the plastic components used in vehicle construction.
The capital letter sequences used for this are standardized in DIN EN ISO 1043-1 and DIN ISO 1629 (for rubber) and can be looked up in the tables which they contain. In addition the string of characters provides information about the exact mixture ratio and the proportion of certain fillers.
Examples of the identification of plastics
NOTE: The identification of the type of plastic is necessary for the plastic welding process in order to determine the correct welding rod (welding material) to use.
If an identifier is missing or cannot be made out, the following easy to perform tests will help:
Visual Inspection
Visual inspections mainly serve to identify PUR and GRP materials. Thermoplastic components are often painted and are therefore difficult to identify.
Identification characteristics:
Mechanical test:
The plastic group can be determined by a sound test:
Sanding test
In this a place is chosen which will not be visible later, and the finger belt sander is used to sand the plastic.
The plastic group can be determined using the pattern of the dust:
Float test in water:
Take a small piece of plastic from the component to be repaired and test whether it floats on water (PP-EPDM, HD-PE, PP) or sinks (PVC/U, PVC/P, ABC, PC).
Nature of the surface
The surface of plastics can be categorized as rigid (PVC-U, PVC-P) and waxy (PP/EPDM, HD/PE, PP).
Adherence test using welding rod
Heat a welding rod that is identified with the type of material and the plastic component using the hot air gun. Press the welding rod onto the plastic component to be welded. When the welding rod cools down, if it remains stuck to the component or can only be removed with great difficulty, then it can be assumed that the two are made of the same plastic. When pulling away from PP/EPDM, HD/PE and PP, this can lead to strings.
CAUTION: Danger of poisoning! When burned, most plastics release vapors harmful to health. Ventilate the room well and use respiratory protection. Where possible work using an extraction system.
Burning test
Every plastic has a characteristic behavior and smell when burned. Using a knife, cut off a small piece from the component to be repaired, remove any dirt and paint residues and set light to the small chip. Now observe the burning behavior. Compare the color, type and smell of the smoke with the results from the following table.
Short description | Plastic recognition using a burning test |
ABS | Blackish smoke, the material drips like a candle when burning and smells like wax. |
PA | No smoke, draws filaments, smells like burnt horn. |
PC | Yellowish, sooty smoke. Smells sweetish. |
PP | No smoke, the material drips like a candle when burning and smells like burnt oil. |
PP/EDM | No smoke, the material drips like a candle when burning and smells like burnt oil. |
PC/PBT | Hard and shiny, burns yellow, fluffy soot. |
Hard PVC / soft PVC | Blackish smoke and acrid smell. |