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Fluoroplastics are being utilized as permeation barriers in a variety of vehicular fuel line, fuel fill and vent, vapor return lines and other applications in order to meet evolving Environmental Protection Agency (EPA) and California Air Resource Board (CARB) hydrocarbon emission standards. This paper will characterize a unique fluoroplastic in terms of properties desirable for these applications which include permeation, flexibility, processability and resistance to a wide variety of fuels. The subject fluoroplastic (known as 3MTM THV Fluoroplastic) has a singular composition of tetrafluoro-ethylene, hexafluoropropylene and vinylidene fluoride.

Elastomer compatibility with fluids to which they will be exposed is one of the important determinants of elastomeric seal performance. Todays hot operating environments often require fluoroelastorners to provide the necessary seal life and reliability. However, there are diierences among fluoroelastomers (due to monomer composition) and among engine oils, transmission fluids and gear lubricants (due to additive and base stock variables). These differences can affect seal performance. Two fluoroelastomers containing tetrafluoroethylene (TFE) and propylene (P) in their structures have demonstrated better and more consistent resistance than FKM types of fluoroelastomers to a wide variety of engine oils, transmission fluids and gear lubricants. This paper demonstrates TFP/P based elastomers maintain their advantage under various time and temperature conditions.

Specification testing has shown FKM fluoroelastomers are significantly affected by newer engine oils, transmission fluids and extreme pressure gear lubricants. A new fluoroelastomer and cure system has been developed which provides better chemical resistance vis-a-vis FKM fluoroelastomers to these fluids. The unique backbone structure of propylene, tetrafluoroethylene and a specific third monomer is different from FKM fluoroelastomers and together with a proprietary cure system accounts for the improved chemical resistance. This new elastomer is available from 3M and it will be referred to as TPT in this paper.

Two new elastomers (a copolymer of tetrafluoroethylene and propylene and a terpolymer of tetrafluoroethylene, propylene, and vinylidene fluoride) demonstrate better chemical resistance to a wide variety of new automotive fluids compared to presently used FKM (FPM) types of fluoroelastomers. The fluids include engine oils, coolants, transmission fluids and extreme pressure (EP) gear lubricants. In addition, one of these new elastomers has shown very little sensitivity to the various additive packages that different manufacturers can use in these fluids.