Enhancing surface adhesion of polytetrafluoroethylene induced by two-step in-situ treatment with radiofrequency capacitively coupled Ar/Ar+CH₄+NH₃ plasma

Although some progress in plasma modification of the polytetrafluoroethylene (PTFE) surface has been made recently, its adhesion strength still needs to be further improved. In this work, the surface of a PTFE sample was treated with a two-step in-situ method. Firstly, the PTFE surface was treated with capacitively coupled Ar plasma to improve its mechanical interlocking performance; then, Ar+NH₃+CH₄ plasma was used to deposit an a-CN_x:H cross-linking layer on the PTFE surface to improve the molecular bonding ability. After treatment, a high specific surface area of 2.20 and a low F/C ratio of 0.32 were achieved on the PTFE surface. Its surface free energy was increased significantly and its maximum adhesion strength reached 77.1 N−10 mm⁻¹, which is 56% higher than that of the single-step Ar plasma-treated sample and 32% higher than that of the single-step Ar+CH₄+NH₃ plasma-treated sample.