Oil Induced Swelling in Thermoelastic Materials

Abstract

The purpose of this thesis was to find a new gasket material to be used in frequency converters manufactured by ABB. The new material has to comply to RoHS directive, because this material is going to replace the currently used material, which is not RoHS compliant. The material is going to be used in conditions, where it may be subjected to chemicals and especially oils, so it should have a good resistance to both. In addition to finding the material, this thesis considers factors affecting elastomer’s swelling in oil. Some requirements were set for the gasket material. The hardness of the material should not be over 60 Shore A and its tear strength should not be less than 23 kN/m. The material should also have a fire classification minimum of V1. The most important criterion was the oil resistance. Gasket material should not swell more than 25 percent from its initial volume when immersed in oil. The literature part of this thesis consists of introducing four material groups which have such properties which are required from the gasket material and considers those properties. These four groups are thermoplastic polyurethanes, styrene-ethylene-butylene-styrene, thermoplastic vulcanizate elastomers and co-polyester based elasto-mers. The literature part also discusses the factors which help estimate the amount of swelling based on the structure of the thermoplastic elastomer. The experiment part of this thesis introduces immersion tests which have been used to determine oil resistance of the test materials. Six materials were tested, the names of the materials are confidential, they are coded to be Materials A, B, C, D, E and F. From these results, the best suited material for the new gasket material was elected. Also from the results, it was possible to determine dependence of swelling on volume, area, vo-lume/area ratio and density of the sample. One suitable material was found in addition to a few others that require more test-ing. The only geometrical factor found to contribute materials swelling was volume/area ratio. Once the graph is made for a certain material, it helps to predict the swelling of a sample with a certain volume/area ratio made from the same material. The tests made for this thesis will continue after this thesis is completed. Some new sample geometries and new materials will be tested. /Kir1