Material Compatibility of Elastomers and Plastics in Ethanol-blended (E10) Gasoline

摘要

Variety of metals and elastomers/plastics are used in vehicle fuel systems. Though higher ethanol in gasoline can lead to efficient burning of fuel, material compatibility of non-metals is one of the major issues of concern. Material compatibility issue needs to be addressed before using higher contents of ethanol in gasoline because of reasons like permeation, swelling, leaching and plasticization, which lead to loss of material properties and subsequently resulting into field failures. For assessment of whether the fuel system will be able to perform as intended for its complete design life, it is necessary to know the impact of use of modified fuel on fuel system components. The impact on the in-use vehicles is particularly important in Indian context, where vehicles even more than 10 years old are plying. Most of the vehicles have not been designed for the 10% ethanol gasoline blend except for a few 4-wheelers. Lack of information on material compatibility with 10% ethanol gasoline blend (E10) fuel in Indian context necessitated actual material compatibility experiments to answer some of the questions about the effects of E10 fuel. Experiments were conducted with E10 and with commercial gasoline (BS-III) as per guidelines given in the standard SAE J1748 on four elastomers and three plastics, commonly used for hoses, seals, gaskets, fuel hose covers, floats, pump housing, hose couplings and nozzles. Material ageing was carried out by immersion of materials in respective fuels at 55°C for specified period (500 hrs for elastomers and 3024 hrs for plastics). Change in material properties like volume/swell, weight, appearance, tensile strength, elongation, impact resistance and hardness Shore A were measured to compare the impact of E10 vis-a-vis gasoline (E0). Tensile strength of all the elastomers was found to be comparable post-immersion in both the fuels. Effect of ageing, in case of plastics, on change in properties was found to be more prominent. The study has revealed the useful information for the vehicle and component manufacturers with respect to the compatibility of the elastomers for their application in fuel system.