Contribution of N2 ion on polar group introduction at PTFE surface by high E/n discharge

Abstract

AbstractPTFE (polytetrafluoroethylene) has superior characteristics such as low dielectric constant, low dielectric tangent, and chemical stability. However, it has a low adhesion force. In order to improve the adhesion force, we have studied the surface modification of PTFE by using a discharge under high E/n (E is the electric field, n is the particle density) conditions in nitrogen. Under high E/n conditions, electrons and ions achieve energies up to and exceeding 100 eV. It is inferred that improvement of adhesion is brought about by the introduction of polar groups at the surface. However, it is not clear which particles (ions, atoms, excited molecules, etc.) in the discharge space promote the introduction of polar groups into the PTFE surface. We assume that ions with high kinetic energies rather than the binding energy of PTFE contribute to the formation of chemical bonds by breaking C‐C or C‐F bonds. It is expected that bond cleavage is the rate‐determining step in surface modification. We measured the contact angle of samples irradiated at various ion energies and exposure doses. The results indicate that increasing the exposure dose accelerates the introduction of polar groups. In addition, it is inferred that an ion energy of about 40 eV is effective for the introduction of polar groups. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(1): 1–7, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21226