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Today's fuel systems place many demands on the seals containing liquid and vapor hydrocarbons. California Air Resource's LEV II and EPA's Tier 2 demands require fuel systems which are essentially hermetically sealed with a robust, long term (12-15 year), life. Two properties which are key to long-term seal life are the material's ability to retain it's sealing force, and the ability to resist fuel permeation. To evaluate these two fuel seal properties, testing was conducted on a number of rubber compounds including HNBR, an HNBR-fluoroplastic alloy, FVMQ (fluorosilicone), an FKM-FVMQ blend, and FKM. To evaluate permeation through a seal, Thwing Albert cups were fitted with stainless steel lids and sealing gaskets prepared from the various test materials. Fuel losses through the gaskets were determined at elevated temperatures. Long term, >1000 hour, stress relaxation testing was conducted in “hot” 60°C fuel and “sour” fuel on these compounds.

Cured-In-Place Gaskets have been demonstrated as a viable, economical sealing choice for a number of automotive applications. Historically, this market has been limited by material choice, which has almost exclusively been the domain of liquid silicone (VMQ) and polyurethane (PU). New technology has been developed which expands the choices of elastomers that can be used in Cured-In-Place gaskets. Seals made with high performance elastomers such as ethylene acrylic elastomers (AEM) and fluoroelastomers (FKM) can now take advantage of this “efficient” process. These materials can be robotically dispensed using equipment similar to what is used in the “hot melt” adhesives industry and then cured with a UV-light source. These UV-cured seals exhibit mechanical properties similar to what their traditionally cured alternatives show and still maintain the excellent heat and fluid resistance of these polymers.

Environmental regulations for reduced hydrocarbon permeation from gasoline powered vehicles and devices encourage development of better fuel hose and tubing as well as improved materials of construction. A review of hydrocarbon permeation regulations will highlight the utility of two new Viton® fluoroelastomer materials for hose and tubing components - VTR-7551 and VTR-9217.

The discovery of Constrained Geometry Catalysts (CGC) for production of polyolefins allows one to make new polyolefins in a solution process. CGCs have a single active site for polymerization, and the bridged nature of the monocyclopentadienyl titanium complex allows facile incorporation of alpha olefins into random ethylene copolymers that are characterized by narrow molecular weight distributions and narrow comonomer distributions. In this paper, olefin copolymers (OCPs) of ethylene with propylene and octene comonomers produced with constrained geometry catalyst are described, and their behavior as viscosity index improvers in oil solutions is examined. A wide range of amorphous and semicrystalline OCPs have been produced and characterized. Crystallinity was measured by DSC, and molecular weights (Mw) were determined by GPC.

Ethylene/alpha-olefin copolymer elastomers based on constrained geometry catalysts exhibit a number of physical properties that make them extremely useful for automotive interior applications. Ethylene/1-octene (EO) copolymer polyolefin elastomers exhibit an optimum combination of properties. Due to the low level of unsaturation in these polymers, they exhibit outstanding heat and UV aging resistance. Their molecular structures enables these polymers to exhibit low glass transition temperatures (Tg). Thus, compositions containing these polymers exhibit very good low temperature impact properties. Furthermore, these products impart inherent flexibility and soft touch to compositions and eliminate the need for plasticizers. These elastomers can be compounded to produce flexible TPO compositions suitable for automotive interior applications

More stringent evaporative emission loss and vehicle life requirements imposed by CARB LEV II and EPA Tier II regulations are necessitating replacement of highly permeable Air Intake and Oil System gaskets with low permeation elastomers. Low permeation, however, is not the only requirement for these gaskets. This paper presents data on fuel permeation, compressive stress relaxation and the low temperature sealing properties of the various elastomer candidates for these seals in order to help the sealing system engineer optimize the overall performance of these gaskets.