In the field of polymer processing, extrusion is one of the most common processing methods. Not only in the processing of recycled materials, also when using virgin polymers there can be contaminations during the storage or processing of the material. This may adversely affect the melt quality and by this also the quality of the final extrusion product. Examples of possible contaminations are metal particles which are caused by wear and tear of the extruder, or degradation products of the processed material itself. As a result of increasing demands on the quality of extrusion products, especially in the field of fibre and film extrusion, the filtration of polymer melts is widely used and state of the art. To remove unwanted debris out of the melt, different metal filter media is used. Some examples of typical filter media are different kinds of wire mesh, filters made of nonwoven metal fibres or sintered metal powder discs. By using this filter media, it is possible to remove foreign particles like solid particles, as well as soft components, so called “gels” from the melt. This ensures a high quality extrusion result. To be able to calculate the lifetime of a filter in an extrusion process, a new possibility of modelling the filter contamination should be presented in this work as a part of the PET processing. At first, a possibility for reproducible rapid contamination of filter materials was developed in pre-investigations. After this, a high number of experimental investigations were done in order to generate a wide data basis for the later on modelling of the filter contamination. This soiling behaviour is then mathematically modelled, so that the filter lifetime can be calculated.