Material Compatibility of Elastomers and Plastics in Gasoline- Ethanol-Methanol Blends 2023-01-0336

The current Indian biofuel policy focuses on the use of alcohol as a potential gasoline blending component to achieve a target of 20% alcohol in gasoline by 2025. The automotive vehicle fuel system uses a variety of metals and non-metals (elastomers and plastics). The fuel system is designed to run with a dedicated fuel, say gasoline or diesel. The use of alternative fuels, i.e., fuels that blend with straight gasoline or diesel, is increasing, and it is critical to understand the impact of these fuels on engine fuel system components. High octane fuels like ethanol and methanol are blended with gasoline to increase engine performance and reduce exhaust emissions, but the alcohols are hygroscopic and corrosive in nature. These fuels' permeation, swelling, and other effects cause changes in material properties. The test fuel is a gasoline-ethanol-methanol (GEM blend of A20 blend), which contains 5% ethanol, 15% methanol, and 80% gasoline. There is no data available on the use of A20 in the Indian context. Hence, there is a need to assess these materials for compatibility issues with the A20 fuel for the intended design life or if there is a modification in the fuel system components.

Material compatibility studies were carried out on materials used in components as per the guidelines given in SAE J 1748 for non-metal (elastomers and plastics) compatibility studies, which are specific for hydrocarbon fuels and their mixtures with oxygenated additives. The sample coupons are immersed in the test fuel at 55 °C in the oven for a period of 1008 hours for elastomers and 3024 hours for plastics. The material properties of elastomers (FKM, NBR, NBR-PVC, and ECO) and plastic material PA66 are evaluated before and after immersion to assess the impact of ageing on materials. The change in behaviour of materials—weight, volume, tensile strength, elongation, and hardness—is elaborately discussed. ECO (wet) and NBR (wet) show better performance in gasoline, and the rest of the elastomers show better or similar performance in all the properties with A20 and E10 fuels. ECO (wet) and NBR (wet) have shown better performance in gasoline, and the rest of the elastomers (FKM and NBR-PVC) show better or similar performance with E10 compared to A20. This study has revealed the material compatibility with the A20 fuel vis-a-vis gasoline/E10 fuels.