The Myth About Low Temperature Performance of Fluoroelastomers in Oil Seal Applications 980850
It is generally believed that vinylidene fluoride (VF2) containing fluoroelastomers, such as di- or ter- polymers of VF2, hexafluoropropylene (HFP), and tetrafluoro-ethylene (TFE), exhibit better low temperature performance than non-VF2 containing fluoroelastomers, such as copolymers of TFE and propylene (P). However, it is found in this study that this is true only for original compounds. The advantage disappears once the compounds are aged. This study was carried out using a dynamic mechanical analyzer by measuring the temperature response of the elastomers before and after aging in a lubricant.
Because of the relative inertness of TFE-P polymers to lubricant additives, it undergoes very little chemical change resulting in practically no change to its low temperature performance. On the other hand, VF2-containing polymers undergo significant chemical changes resulting in a degradation of their low temperature performance. Consequently, after aging, both types of polymers behave similarly at low temperatures, while TFE-P type polymers provide the additional advantage of improved chemical resistance.