Performance Studies of Ethylene-Propylene Rubber Automotive Coolant Hoses
Ethylene-propylene rubber compounds have been utilized in automotive coolant hoses for more than twenty-five years. Throughout this period, hose compositions have continually evolved to meet ever changing requirements of long-term serviceability, higher heat resistance, coolant fluid compatibility, and non-bloom features for the cover. Despite the commercialization of compounds with improved quality and consistency, radiator and heater hoses in certain vehicle models and designs develop cracks well before their expected service life capability. While all hoses including these failures are being exposed to higher levels of heat duress, physical property deterioration, via the usual auto-oxidation mechanism, does not alone seem to be the major cause. This paper describes the nature of coolant hose cracking failures and laboratory studies to explain the observed striae, dendritic structures, and coolant exudation within the hose.