VDA 675-291 (11/2020)
VDA 675-291: Elastomer-Bauteile in Kraftfahrzeugen - Prüfverfahren zur Eigenschaftsbestimmung - Probenvorbereitung: Trocknen von Probekörpern / Elastomers Test Procedure for Identification - Sample Preparation: Drying of test pieces (Version 11/2020) - Gruppenlizenz (group license), AGB (GTC) Art. 10, 2
During storage of post-cured, minerally filled elastomers changes in the physical properties can occur, where the extend is dependent from the water content in the atmosphere and from the compound composition. The usual conditioning of the test pieces cannot compensate the changes caused by this effect, which is called drifting. The changes which occured during storage can be removed reversibly by additonal heating.
Good practice requires precise reference values, to which the relative changes of material properties can be referenced after media immersion. After storage in heat or in hot operating media (e.g. oil) the test pieces are in an as it were „water-free“ condition. The test pieces to determine the reference values must be in this condition as well. This conditon can be reached by drying the test pieces. Drying is only required for the determination of the reference values (values in delivery condition). Drying is only necessary for post cured, minerally filled elastomers and is only performed, when explicitely required by the elastomer compound manufactuer.