Experimental and Analytical Tools for the Chemical Recycling of Engineering Plastics - A Multi-Scale Pyrolysis Study...

The creation of a circular economy for plastics is essential for a sustainable future. Currently, established recycling processes are not universally applicable. Pyrolysis can complement current recycling through the conversion of complex plastic wastes to condensates and gases for reintroduction into chemical industry processes. A multi-scale approach for the characterization of pyrolysis properties is presented using the example of polydicyclopentadiene. Pyrolysis-GC-MS (µg-scale), thermogravimetric (mg-scale), and lab-scale (g-scale) pyrolysis investigations are complemented by high-resolution product analytics. In Py-GC-MS, 1,3-cyclopentadiene is abundant, hinting at depolymerization as a dominant decomposition mechanism. In thermogravimetry, approx. 20 mass-% of the sample is converted to solids. On lab-scale, secondary reactions influence the product yield and spectrum significantly, indicated by a solid yield of ≈40 mass-%. Polydicyclopentadiene exhibits a broad product spectrum comprising unsaturated hydrocarbons and aromatics. In the condensed product, no 1,3-cyclopentadiene is detected, indicating recombination or derivatization reactions. Significant solid residue formation emphasizes scaling effects. The employed analytics provide comprehensive analyses of condensed and non-condensed products. With the presented approach, primary and secondary mechanisms can be resolved and crucial process parameters identified. In this way, a powerful toolset for the development of robust pyrolysis processes that aid in achieving circularity for plastics is provided.