# Compatibility of Different Automotive Elastomers in Paraffinic Diesel Fuel
## 2 Materials and Methods
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Property** & **Unit** & **Test Method** & \begin{tabular}{c} **EN 590** \\ **Requirement** \\ \end{tabular} & \
\begin{tabular}{c} **Results** \\ **DF** \\ \end{tabular} &
\begin{tabular}{c} **Results** \\ **GTL** \\ \end{tabular} \\ \hline Cetane index & – & EN ISO 4264 & min 46.0 & 56.2 & 53.1 & 84.2 \\ \hline Density at 15 \({}^{\circ}\)C & kg/m\({}^{3}\) & EN ISO 12185 & 820.0–845.0 & 822.9 & 833.9 & 777.9 \\ \hline Viscosity at 40 \({}^{\circ}\)C & mm\({}^{2}\)/s & EN ISO 3104 & 2.000–4.500 & 2.685 & 2.772 & 2.660 \\ \hline Flash point & \({}^{\circ}\)C & EN ISO 2719 & min 55.0 & 58.5 & 62.5 & 70.0 \\ \hline Sulphur content & mg/kg & EN ISO 20846 & max 10.0 & 6.8 & 6.9 & \textless{}3.0 \\ \hline Cold filter plugging point & \({}^{\circ}\)C & EN 116 & \(-\)10 for D grade & & & \\ Cold filter plugging point & \({}^{\circ}\)C & EN 116 & \(-\)15 for E grade & \(-\)16 & \(-\)15 & \(-\)21 \\ \(-\)20 for F grade & & & & & \\ \hline Lubricity HFRR at 60 \({}^{\circ}\)C & \(\upmu\)m & EN ISO 12156-1 & max 460 & 413 & 202 & 476 \\ \hline Aromatics & \% (\(\
u/\
u\)) & D1319 & - & 20.3 & 19.7 & \textless{}1.0 \\ \hline FAME content & \% (\(\
u/\
u\)) & EN 14078 & max 7.0 & \textless{}0.1 & 6.6 & \textless{}0.1 \\ \hline Copper strip corrosion & & & & & \\ (3 h, 50 \({}^{\circ}\)C) & classification & EN ISO 2160 & 1 & 1a & 1a & 1a \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of tested fuels. Percentage volume change was calculated from [44]:  
\[\Delta V=\frac{(M_{2}-M_{4})-(M_{1}-M_{3})}{(M_{1}-M_{3})}100\ [\%] \tag{2}\]  
where \(M_{3}\) is the initial O-ring mass in water [g] and \(M_{4}\) is the O-ring mass in water after immersion [g]. Each O-ring was measured 7 times, providing an arithmetic mean, later adopted as the measurement result. The measurement error for mass and volume was 0.5% of the measured value, and 0.4% for hardness. In the presented figures, the vertical error bars correspond to the measurement uncertainty. The last stage of the research involved microscopic observations. Microscopic methods are commonly used to visualize the surface condition of polymeric materials. It is no different with the characteristics of rubbers exposed to fuels. A dedicated microscope is used depending on the needs and the order of magnitude of the studied changes and objects. Examples include the application of electron microscopy (e.g., SEM) and atomic force microscopy (AFM) to identify material and structural changes on a nanometric [45] and micrometric [46] scale, or the employment of optical microscopes for micro-scale surface imaging [24; 47]. The observations were conducted by means of a Nikon Eclipse LV100 ND optical microscope with a Nikon DS-Ri2i camera and NIS-Elements BR software. Microscopic imaging was undertaken using the bright field (BF) technology. The following magnifications were involved during the analysis: 10 \(\times\) 10--200 \(\upmu\)m scale, 10 \(\times\) 20--100 \(\upmu\)m scale, 10 \(\times\) 50--50 \(\upmu\)m scale. Prior to the observations, each seal was purged with dry air in order to remove potential contaminations, followed by rinsing with 96% ethanol of analytical grade and being left to dry.