A Novel Fluorocarbon Elastomer for High-Temperature Sealing Applications in Aggressive Motor-Oil Environments

Abstract

The tendency in the automotive industry to use smaller engines has resulted in a situation where lubricating oils are exposed to higher operating temperatures. This is especially the case in countries where there is no restriction on highway speed. Amine-based additives present in the oils (e.g., as dispersants and corrosion inhibitors) tend to slowly attack the conventional fluorocarbon elastomer seals under these conditions. As a result of that attack, the seal becomes brittle and eventually fails. A novel fluorocarbon elastomer of vinylidene fluoride, tetrafluoroethylene, and propylene has shown excellent aging behavior in the laboratory toward many aggressive engine oils at elevated temperature. Its improved resistance as compared to conventional fluorocarbon elastomers is attributed to the replacement of hexafluoropropylene with propylene.

Cure Systems for Fluoroelastomers

“…During the early 1970s, DuPont workers made terpolymers containing 526 mole % VDF, 5065 mole % TFE, and 20 45 mole % P that were curable with diamine carbamate crosslinkers and quaternary ammonium or phosphonium accelerators. [49] Resistance to automotive motor oils was compared to that of bisphenol-cured VDF/HFP dipolymer and peroxide-cured VDF/HFP/TFE terpolymer; representative results are shown in Table 5.10. [47] Further improvements in bisphenol curing of TFE/P/VDF terpolymers were made at 3M by Grootaert and Kolb, [48] who found more effective accelerators for polymers containing high levels of VDF.…”

“…10 Comparison of TFE/P/VDF with VDF/HFP/(TFE) Elastomers[49] Polymer VDF/HFP VDF/HFP/TFE/Br-CSM TFE/P/VDF % Change in properties after exposure to 10W/30 SG/CC motor oil, 168 h at 160ºC…”

Unsaturated bond existing in tetrafluoroethylene–propylene–vinylidene fluoride terpolymer

“…On the other hand, an excess of VdF content results in a loss of resistance to base, such as amines formulated in engine oils and coolants, etc. for high performance [1][2][3].…”