HFRR test method with stainless steel specimens for gasoline fuels

Reducing CO2 emission is a major challenge for the automotive industry. The different fuels (E10, E100, M15 etc.) that are used for gasoline systems not only influence the CO2 emission but also significantly influence the friction and wear behavior and subsequently the lifetime of powertrain components. The effect is much higher when biofuels are used. The characterization of tribological properties of gasoline fuels is necessary for a robust design which allows for permanent control of performance. The High Frequency Reciprocating Rig (HFRR) test concept according to ISO 12156 is the standard test method for evaluating the lubricity of diesel fuels. Up to now, no standard for gasoline fuels is known. The standardized HFRR test method uses 100Cr6 test specimens which are stable in contact with diesel fuel, but, unlike the stainless steel components used in gasoline fuel injection systems, is prone to corrosion in a gasoline environment typically containing a certain amount of water. This paper aims to develop a lubricity test method with stainless steel for gasoline fuels and reports first results for various fuel compositions

Untersuchungen des Oberflächenglasüberganges von Polystyrol mittels des Einbettens von Edelmetall-Clustern

The temperature dependent embedding process of noble metal nanoclusters into polymers was used to probe the surface glass transition. X-ray photoelectron spectroscopy (XPS) was applied to study the embedding of Au nanoclusters into polystyrene. A small decrease of glass transition temperature (Tg) at the surface compared to the bulk, which decreases at low Mw, was detected with this method. In order to understand the Tg depression in monodisperse polystyrenes measurements were performed on bimodal mixtures of monodisperse polystyrenes. The results on the bimodal mixtures rule out the interpretation that the Tg depression at the surface is due to an enrichment of shorter chains. Transmission electron microscopy (TEM) investigations yield the same cluster sizes and densities for a height and a low molecular weight. Therefore, probe size effects can be excluded. The Tg of thin PS films was additionally determined by the charging and discharging during XPS measurements