Inline Analysis of the Plastics Melt Emissions in Real Time During Mechanical Recycling Using the SIFT-MS Method

The quality of recycled plastics is significantly influenced by the contamination content of volatile organic compounds (VOCs), which enter the plastic through additives, migration or degradation processes. This poses a challenge for applications with high chemical requirements, such as food and cosmetics packaging or components in automotive interiors. In addition, previous analytical methods are based on random samples and only analyze a fraction of the material. Particularly with inhomogeneous input streams, there is a risk that potentially harmful substances will not be detected. For this reason, this study investigated the suitability of Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) for the continuous inline analysis of VOCs during the extrusion process. By measuring the gas flow in real time at a vacuum dome of a twin-screw extruder, various VOCs from the input materials, including limonene and model substances in accordance with FDA requirements, were clearly identified and quantified. The measurement results showed a high correlation between the VOC content in the input material and the concentration in the gas flow. The results demonstrate the potential of SIFT-MS for process monitoring and quality control in mechanical plastics processing, especially for increasing safety and traceability when using recycled materials in sensitive applications.