Permeation and Stress Relaxation Resistance of Elastomeric Fuel Seal Materials

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. The results of the permeation though sealing materials and the stress relaxation in fuel will be presented in this paper.