Plastics are made of polymers and additives. For good manufacturing behaviors special additives are added. Some additives were used for a better ejection and flow behavior. To get an proper classification of additives, new in-line measurements were developed. The flow behavior of plastics can be determined with an in-line viscosity measurement in an injection mold. To classify the ejection behaviour during the injection molding process, the ejection force and the normal force were used. The new in-line measurements allows a detailed classification of processing aids in plastics.