Short-time plasma pre-treatment of polytetrafluoroethylene for improved adhesion

Fluoropolymers with their unique properties (chemical inertness, thermal stability, low surface tension, mechanical stability) are used in many industrial applications. One disadvantage of these fluoropolymers is their poor adhesion to other materials. In this work a short-time plasma pre-treatment of polytetrafluoroethylene (PTFE) with a low pressure microwave plasma was investigated. The Plasmodul® source allows the pre-treatment of PTFE substrates with an ammonia plasma (NH3). The newly developed plasma source Planartron®, which is derived from the Duo-Plasmaline®, was used for improving the adhesion properties of PTFE by generating oxygen and nitrogen plasmas. PTFE foils were modified on both sides by plasma treatment for typically 30 s. After bonding the foils to aluminum dollies using a 2-K-epoxy resin the bonding strength of the adhesive joint was measured directly by pull off tests. Some modified foils were additionally investigated by Fourier-transform infrared spectroscopy.