Study on the adhesion of PTFE/PI composite films by interlocking synergistic effects

Composite films of polytetrafluoroethylene (PTFE) and polyimide (PI) combine the advantages of both materials like excellent inertness to chemicals and thermal stability, which provide great potential in applications under harsh environments. However, strong adhesion between PTFE and PI layers still remains a big challenge. In this study, fluorinated ethylene propylene (FEP) as an intermediate layer was found to significantly enhance the adhesion of PTFE films to PI film, with peel strength up to 350 N/m in the manufactured direction comparing to the value of 0 for PTFE/PI composite film without FEP. It’s superior to that of commercially available products (25 N/m) under the same test conditions. The improved performance is attributed to the formation of interlocks of molecules at the interfaces between the PTFE and FEP layers, and FEP and PI layers as observed in the images obtained by atomic force microscope (AFM) and scanning electron microscopy (SEM).