The Effect of Lubricating Oil Additives on the Properties of Fluorohydrocarbon Elastomers

Fluorohydrocarbon elastomers are well known for their resistance to heat and fluids. However, certain additive packages in lubricating oils have been found to have a deleterious effect on the properties of these rubbers. Consequently, a study was undertaken to determine the effect of oil additive on the properties of fluorohydrocarbon rubbers under total immersion conditions. Most of the tests were conducted at 163°C to accelerate the effects that might be observed under normal automotive operating temperatures. Performance was based on the change in elongation, degree of crazing and volume increase.

Of the several classes of additives tested, only the strong nitrogenous organic bases or compounds which decompose to form strong bases had a deleterious effect on the elongation. Additives have been identified which perform functionally similar to these strong bases but without exerting harmful effects. Properly compounded, high fluorine-containing fluoropolymer rubbers have been demonstrated to provide excellent resistance to attack by strong bases present in many commercial lubricants.

The different performances of rubbers in lubricants are usually, but not exclusively, due to the chemical composition of the additive packages. Future consideration by the lubricating oil industry for the formulation of additive packages, based on the rubber materials to be used, would greatly increase the reliability and serviceability of seals and other elastomeric components.