In the research project "PTFE-Sub", the SKZ plastics centre and Innovent e. V. are developing sol-gel coatings for plastic welding. They are intended to replace the widely used coating systems based on polytetrafluoroethylene (PTFE) with PFAS-free, durable and energy-efficient alternatives. The two-year project started in August 2026.
Limits of PTFE in welding
PTFE coatings and PTFE glass fabric films provide good non-stick properties in heated tool butt welding of plastic pipes made of polypropylene (PP) or polyethylene (PE) and of window profiles made of polyvinyl chloride (PVC). In hot gas extrusion welding, PTFE is used as the material for welding shoes. However, its comparatively low wear resistance leads to frequent maintenance and replacement intervals. In addition, PTFE and other PFAS-containing materials are increasingly in focus because of possible future regulatory restrictions.
Sol-gel systems with tailored additives
The new coatings are intended to combine high temperature resistance, pronounced non-stick and sliding properties and significantly improved wear resistance. In addition, the tools should be easy to repair or recoat. The sol-gel systems are adapted to the requirements of different welding processes by means of suitable additives. Specially built test rigs are used to examine wear, non-stick and sliding properties under realistic conditions; the coatings are then to be validated in welding trials with PE and PVC components.
"With PTFE-Sub, we want to show that high-performance non-stick coatings are also possible without PFAS. Our goal is to provide companies with a sustainable and economically attractive alternative to today's PTFE systems," says Patrick Witzel, head of the Thermal Joining research group at SKZ.
The aims are longer tool service lives, lower maintenance costs and greater process reliability. PTFE fabric films and PTFE welding shoes, which are difficult to recycle, are to be replaced by durable alternatives. The results are aimed in particular at small and medium-sized companies in plastics processing, pipeline construction, window manufacturing, apparatus and container construction and surface technology. The project is funded under the Industrial Collective Research programme (IGF) (01IF25312N).