Less than 10% of all produced thermoplastics are recycled at the moment. Obviously, this number hast to be increased. Nevertheless, for the already being recycled materials improvements have to be made, which is also as an incentive to promote the circular economy. In the beginning plastic recycling streams usually consist of a mixture of different plastic types especially considering household waste. Although the sorting and washing technologies are improving strongly and even well prepared recycling materials are achieved, there still can be a non-neglectable number of foreign plastics in the material stream. Therefore, we have developed an inline material monitoring system with the help of Raman Spectroscopy for mechanical recycling machines. Since Raman spectroscopy is getting increasingly popular in polymer processing this kind of spectrometer was used as detection device. The system is applied in a step where a representative material mix passes the measurement spot very quickly which offers the possibility to use appropriate laser intensities for sufficient information quality. One application is the identification of PP in an LDPE stream which makes up a major share of recycling materials. To gain a continuous quality for recycled LDPE film blowing materials a certain amount of PP must not be exceeded. The developed system can detect the amount of PP in the PE fraction during processing. The advantage of this system is that the detection can be carried out in a continuously moving pre-processing step, where the material is passing by the probe head with a good statistical distribution. Based on these information control concepts are developed enabling the separation of PP to a separate silo if a certain level is detected. With this method it is possible to react quickly on changing material conditions such as the inline detection of specified polymers as well as for an automated process control.