Experimental investigations on material compatibility of a methanol fuel supply system of a spark ignition engine

Material compatibility of fuel supply system comprised of different materials including elastomers (nitrile, polyvinyl chloride (PVC) nitrile, chloroprene, natural rubber and ethylene-propylene-diene monomer (EPDM)), aluminium and fuel filter (outer tin coated circular plate and paper) with methanol was studied. The specimens of the parts of the fuel supply system were immersed in methanol for a period of ninety days under atmospheric conditions. The properties of the specimens such as physical changes using scanning electron microscope (SEM) image of the surfaces and mechanical properties including tensile strength and strain at break were studied. It was observed from the images that the coating over the circular plate of fuel filter eroded while elastomers developed a whitish coat on their surfaces. SEM images indicated surfaces of EPDM, chloroprene and natural rubber were damaged significantly. Diffusion of methanol inside the elastomers negatively impacted on the increased mass of rubber specimens whereas, with PVC nitrile and EPDM, the swelling was negligible. SEM image showed mild deterioration of aluminium surface. Furthermore, tensile strength of natural rubber, chloroprene, nitrile and PVC nitrile decreased by 29.3%, 59.8%, 31.2% and 33.2% respectively. Decrease in strain at break was significant with chloroprene, nitrile and PVC nitrile rubbers. A notable conclusion emerged from the study that EPDM performs satisfactorily with methanol since deterioration of its mechanical properties and swelling was negligible.