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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.

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.

Prevailing trends in automotive powertrain applications are pushing current elastomeric seal materials to their limits. These trends include the push towards higher temperatures under the hood; longer warranties up to 100,000 - 150,000 miles and 10 - 15 years; and increasingly more stringent environmental regulations. These trends are combined with an expanded use of fluids containing additives that are more aggressive towards elastomeric materials, and the use of low viscosity fluids for improved low temperature performance in automatic transmission and hydraulic fluids. In this presentation traditional fluoroelastomer compounds used in automotive powertrain sealing applications will be compared to several new specialty types of fluoroelastomers that are designed to help both the end user and rubber part manufacturers solve difficult sealing problems. Specifically, fluoroelastomer polymers, with both improved low temperature properties and fluid resistance will be reviewed.

Compression stress relaxation is becoming an increasingly useful tool to determine how well a sealing material will perform in various environments. While stress relaxation data has been published on some rubber materials, there is very little recent data for ethylene/acrylic elastomer, even though it is one viable option for engine and transmission gasket applications. In addition, three new grades of ethylene/acrylic elastomer have been recently commercialized, all of which make very suitable gasket materials. This makes it very timely to investigate the performance of this family of sealing materials. The purpose of this paper is to measure compression stress relaxation for these new grades of ethylene/acrylic in both SG engine oil and automatic transmission fluid for extended periods of time. The results of the ethylene/acrylic grades will also be compared to those of functionally competitive materials, such as polyacrylate and silicone.