# Compatibility of Different Automotive Elastomers in Paraffinic Diesel Fuel
###### Abstract  
The introduction of new fuels to power internal combustion engines requires testing the compatibility of such fuels with materials commonly used in fuel supply systems. This paper investigates the influence of alternative fuels on the acrylonitrile-butadiene rubber and fluoroelastomer used in the automotive industry. In the study, conventional diesel fuel, its blend with 7% of fatty acid methyl esters and paraffinic diesel fuel produced with the Fisher Tropsch synthesis from natural gas were interacted with the elastomers. The immersion tests were carried out at room temperature (20 \({}^{\circ}\)C) for 168 h. The effect was evaluated based on changes in the selected rubber's volume, mass and hardness. It has been confirmed that the synthetic component without aromatic hydrocarbons had a different effect on the tested rubber than did conventional fuel. In follow-up work, the selected rubbers were also subjected to microscopic observation. The most frequently observed effect was the washing out of the seal protective layer. acryonitrile-butadiene rubber; fluoroelastomer; gas to liquid; material compatibility; paraffinic diesel fuel +
Footnote †: journal: _aciences_  
and the processing of animal fats [6]. FAME can be added to diesel fuel as a fuel component. The advantages of their incorporation include biodegradability [7], better lubricating properties [8] and low emission profiles. Such components are non-toxic [9]. At the same time, it should be noted that the chemical composition of FAME is different from diesel, hence the content of FAME in commercial fuels was limited to 7% (\(v/v\)) (B7), while fuels containing more esters can be used in vehicles dedicated exactly for this fuel type [10]. Incorporation of this component also comes with downsides, which include less stability than fossil diesel fuel, worse low-temperature properties [11], greater hygroscopicity and higher fuel consumption. It may also have an adverse impact on natural and nitrile rubber seals [12]. Similar to conventional diesel fuel, its properties strongly depend on the raw material used for its production [13]. The introduced amendment to the Directive of the European Parliament and of the Council (EU) 2018/2001 on 11 December 2018 [14] has limited the possibility of using conventional biofuels made of raw food materials. This promotes advanced alternative fuels of inedible raw materials or waste, and will intensify the growth in the share of these components in fuels over the next decade. However, before the EU reaches zero emissions in the passenger car sector in 2050 [15] and the replacement of diesel engines by electric motors [16] comes about, during this transition period, vehicles will be powered by alternative hydrocarbon fuels. The literature contains studies in which their authors point to the possibility of using various fuels for powering diesel engines. These include FAME (in amounts higher than the standard 7% (\(v/v\))) [17], vegetable oils [18], dimethyl ether DME [19], butanol [20], pyrolysis oil [21] or synthetic fuels [22]. Some of these can only be used as a fuel component, while DME and synthetic fuels constitute complete substitutes. Two synthetic fuels for diesel engines can be distinguished at the current moment. These are paraffinic diesel fuels obtained through the hydrogenation of fatty acids from HVO (hydrotreated vegetable oil) and through synthesis process [23], e.g., gas to liquid (GTL). Unlike other alternative fuels, synthetic fuels are composed of the same hydrocarbons as fossil fuels, albeit with a lower variety. Therein, paraffin hydrocarbons are predominant and they contain no aromatic hydrocarbons at all. Aromatic compounds are characterized by very good low-temperature properties and calorific values; however, they exhibit poor self-ignition properties. Furthermore, they have worse thermal stability, and lead to the swelling of rubber seals, hence bringing about very tight connections in the distribution and fuel supply systems [24].