The SKZ Plastics Centre is working with industry partners to develop a continuous process for recycling silicone elastomer waste. In this process, the silicones are depolymerised into monomers in a planetary roller extruder, from which new silicones can be synthesised. This avoids the energy-intensive process of producing virgin monomers and increases sustainability.
With the announcement of the European Green Deal in 2019, the European Union is pursuing the goal of becoming the first continent to achieve climate neutrality by 2050. A key area for achieving the Green Deal's environmental protection goals is the transition to a circular economy. Resource savings through recycling play an important role here.
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The silicone elastomer recycling project combines the expertise of the partners in the fields of silicone production and chemistry, material comminution, chemical process design and compounding in planetary roller extruders (Photo: WACKER, Mercodor, ENTEX, SKZ) |
The production of silicones is energy-intensive. It also generates CO₂, which is chemically unavoidable. The production of metallurgical silicon, which is required for the synthesis of silicone monomers, is responsible for 66% of the greenhouse gases produced. At the same time, silicones are crucial for applications in key industries such as medicine and energy technology, as well as the automotive and electrical industries, due to their outstanding properties. Silicones have high biocompatibility, temperature resistance, chemical resistance and weather resistance. The SKZ Plastics Centre is working with partners from industry to find a solution for recycling this group of materials.
Silicones are cross-linked materials. This chemical cross-linking is the reason for their high durability and many of their positive properties, but it also makes recycling the material particularly challenging.
‘Another important aspect of this project for us is to develop a continuous process that can also be implemented economically in industrial quantities,’ explains Dominik Uhl, scientist in the Cross-linked Materials department at SKZ.
The aim of the new research project is to develop a continuous depolymerisation process in a planetary roller extruder for recycling silicone waste. Such a process does not yet exist on a technical scale and is to be implemented for the first time in a laboratory setting at SKZ. This will enable the recovery of directly processable monomers that can be used to synthesise new silicones. This would reduce the amount of new material required. The development of this process represents the first step towards significant energy savings in the production of silicones and the establishment of a circular economy for this class of materials as well.
The starting signal has been given for the pioneering research project on silicone recycling: Together with its industry partners ENTEX Rust & Mitschke GmbH, Mercodor GmbH Sondermaschinenbau KG and Wacker Chemie AG, SKZ is developing a continuous recycling process for silicone elastomers through depolymerisation in a planetary roller extruder. This project will be funded by the German government's 8th Energy Research Programme from 1 August 2025 to 31 July 2028.
