Influence of Engine Coolant Composition on the Compatibility of EPDM Hose Materials

The use of glycol based coolants in combination with EPDM hose materials has been used in the internal combustion engine for over 25 years. EPDM remains the most widely used elastomers due to its advantageous price to performance ratio in this field of application. The major car manufacturers are calling for better fuel consumption by means of weight reduction and improved aerodynamics of the car. These two factors lead to a steady and continuous increase of the under-bonnet temperatures. Consequently the operating temperatures of the cooling circuits have increased. New metal alloys are used for the production of engines in order to reduce weight. These new metal alloys coupled with the higher temperatures dictate appropriate changes in the composition of cooling liquids. Particular attention has to be paid to the stabilisation packages and modification of the materials used in the EPDM hose. These changes lead to an influence of the long-term performance of EPDM hose materials. Several EPDM hose materials are immersed in different coolants under various ageing conditions. The influence of EPDM hose material composition is evaluated with respect to change in physical properties, electrochemical degradation behaviour and formation of sediments in relation to change in coolant composition.