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Thermal Depolymerization Challenges of PTFE:Silicone Rubber Mixtures and Composite Materials
Lukas Eigenschink1,2, Matthias Mastalir3, Michael Harasek2
1Institute for Chemical Technology of Organic Materials, Johannes Kepler University Linz, Altenberger Straße 69, 4040 Linz, Austria.
Polymers
|August 13, 2026
Summary
Co-pyrolysis of polytetrafluoroethylene (PTFE) and silicone rubber (SR) yields complex products, including PFAS. Recycling strategies must account for non-additive degradation in these polymer composites.
Area of Science:
- Materials Science
- Polymer Chemistry
- Chemical Engineering
Background:
- Thermochemical depolymerization is challenging for polymer mixtures due to complex degradation.
- Polytetrafluoroethylene (PTFE) and silicone rubber (SR) individually depolymerize well, suggesting recycling potential.
- PTFE and SR are often combined in composites, necessitating understanding of their co-pyrolysis behavior.
Purpose of the Study:
- Investigate the pyrolysis behavior of PTFE:SR mixtures and composites.
- Analyze product composition and mass balance during co-pyrolysis.
- Identify limitations for depolymerization-based recycling of PTFE:SR systems.
Main Methods:
- Pyrolysis experiments on virgin PTFE, SR, mixtures, and composites (e.g., PTFE-lined tubing).
- Product analysis using Gas Chromatography-Mass Spectrometry (GC-MS), Nuclear Magnetic Resonance (NMR), and Fourier-Transform Infrared Spectroscopy (FTIR).
- Evaluation of mass balance and formation of new chemical species.
Main Results:
- Co-pyrolysis exhibits a non-linear product distribution dependent on PTFE content.
- Si-O and Si-CH3 bonds cleave, forming fluorinated siloxanes and per- and polyfluoroalkyl substances (PFAS).
- Low PTFE content favors cyclic siloxane formation; higher PTFE content increases PFAS and difficult-to-valorize fluorinated silicon species.
Conclusions:
- Depolymerization strategies for pure polymers are unsuitable for PTFE:SR composites.
- Low PTFE content systems show some promise for depolymerization.
- High PTFE fractions complicate recycling due to PFAS and fluorinated silicon byproducts, posing challenges for monomer recovery.
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