Deterioration of seals of automotive fuel systems upon exposure to straight Jatropha oil and diesel

Straight vegetable oils (SVO's) are currently used as renewable sources of fuel in diesel engines for electricity production, transport or agricultural mechanization. Despite various environmental benefits, the use of SVO's may result in shortcomings for the engine operation, in particular, degradation of seals and polymeric components. Thus, deterioration of seals into contact with SVO's in engines must be analyzed to make a safe use of these alternative fuels. In this work, the deterioration of silicone rubber (VMQ), fluoroelastomer/Viton® (FKM), ethylene-propylene-diene monomer (EPDM) and neoprene/chloroprene rubber (CR), upon exposure to straight Jatropha oil (SJO), diesel, and a blend 80% diesel-20% SJO (B20), respectively, was analyzed by immersion tests with measurements of changes in mass, volume, tensile and tear strengths, and hardness. Complementary measurements of changes in viscoelasticity, surface morphology, topography, and chemical composition provided further insight into the understanding of deterioration of the elastomers. Overall, the four elastomers exhibited negligible deterioration with SJO while only FKM exhibited minimal deterioration with diesel and B20. VMQ and FKM were the less deteriorated elastomers by SJO and diesel, respectively. These experimental results were found to be in good agreement with predictions of compatibility based on the use of the Hansen solubility theory.