ABSTRACT
The elastomer compound used for the study is an AEM. It was provided in the form of 2 mm sheets and compression set cylinders. Then a punch was used to make either compression or tensile samples.
2.2 Methods
The dynamic tests were conducted on a Metravib DMA+450. The frequency used for the experiments was 5 Hz and the temperature slope 1°C/min. The monotonic uniaxial tensile and compression tests were conducted on an MTS dynamometer at very
1 INTRODUCTION
SOGEFI is a global supplier to automotive industry and is specialized in fluids filtration. Our products have to withstand fluids temperature underhood in the range 80-150°C but even low temperatures. In some countries, the temperature can decrease to −40°C and our filters modules have to be tightness. In this study we focused on oil tightness and more particularly, how to predict tightness at low temperatures. SOGEFI chose the Ethylene-Methyl Acrylate Rubber family (AEM). This material was chosen taking into account its relative tolerance to high temperature and its low cost. Thus, the application temperatures being near or below the glass transition temperature (Tg), SOGEFI required the rubber expertise of the French Rubber and Plastics Research and Testing Laboratory (LRCCP). The physical properties of amorphous polymers change significantly in the Tg region Ferry (1981). For static and dynamic seals, the changes in physical properties may result in a poor sealing which may be recurrent depending on the operating conditions. Firstly, mechanical tests were carried out on the AEM compound to describe the physical phenomena causing seal failure at low temperatures. In particular, an original testing device was designed to evaluate the evolution versus time of
low strain rate of 1%/min. The thermal expansion coefficient was measured by LNE (Laboratoire National de métrologie et d’ Essais) from −100 to 150°C with a temperature slope of 5°C/min. The Figure 1 shows an image of the experimental apparatus. A compression set sample is used for these experiments. The maximum solicitation occurs in compression along a diametric axis. The sample was compressed at 30% strain and 20°C and no additional adjustment was made to the end of the test. The experimental temperature profile is displayed in Figure 1 right. The experiment started with a 4-hours isothermal stress relaxation period. Then the temperature is decreased by 10°C at maximum speed. This step is followed by a 4 hours isothermal relaxation period. Then the temperature is decreased by 5 or 10°C steps until reaching −40°C. This non standard experiment approaches actual conditions of use. Its results will be used as validation for the constitutive law. As the stress field is not uniaxial, the load versus experimental time will be displayed.
