Enhancing adhesion between metals or epoxy and polytetrafluoroethylene by ion assisted reaction
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Enhancing adhesion between metals or epoxy and polytetrafluoroethylene by ion assisted reaction S. K. Koh, J. W. Seok, S. C. Choi, W. K. Choi, and H. J. Jung Division of Ceramics, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, Korea (Received 10 March 1997; accepted 7 June 1997)
Ion irradiation on polytetrafluoroethylene (PTFE) has been carried out to improve adhesions to metals and to adhesive cements. Argon ions were irradiated on the polymer, by varying the amount of Ar1 from 1 3 1014 ionsycm2 to 1 3 1017 ionsycm2 at 1 keV, and 4 mlymin of oxygen gas flowed near the polymer surface during the ion irradiation. The wetting angle of water on the PTFE surface was changed from 100± to 70–150±, depending on the ion beam condition. The changes of the wetting angle and effects of Ar1 irradiation in oxygen environment were explained by the changes in surface morphology due to the ion beam irradiation onto PTFE, and formation of a hydrophilic group due to a reaction between the irradiated polymer chain and the blown oxygen. Strongly enhanced adhesion is explained by interlock mechanism, formation of electron acceptor groups on the modified PTFE, and interfacial chemical reactions between the irradiated surface and the deposited materials.
I. INTRODUCTION
Many attempts to alter surface properties such as wear resistance,1 solubility,2 adhesion,3,4 etc. have been shown by various ion beam irradiation techniques. Polytetrafluoroethylene (PTFE) has been applied in various areas for chemical ineptness, thermal and mechanical stability, and electric insulation. High energy ion irradiation (several keV–MeV),5–7 ion assisted deposition,8 etc. has been carried out to improve adhesion between PTFE and others, and successful results by a tape peeling test have been reported. Chemical analysis has been carried out to understand phenomena at the metal-PTFE interfaces using X-ray Photoelectron Spectroscopy (XPS)9 and M¨ossbauer spectroscopy.10 High energy ion irradiation on polymers can improve those properties such as wear resistance, solubility, adhesion, etc. that are mainly related to clean surfaces and can change the chain length of polymer. However, generation of high energy particles (.100 keV) and formation of large area ion beams (.100 cm2 ) are not easy for the industrial applications. The effects of the ion beam irradiation on polymers are chain scission, double bond formation, crosslinking network, and creation of new functional groups,11–13 but it is not easy to control these effects independently. In this article, we modified the PTFE surface by keV Ar1 ion irradiation which is higher energy than the chemical bond energy of polymer chain, and investigated surface phenomena induced by the ion beam irradiation in oxygen environment, so called, ion assisted reaction (IAR).14–16 Enhancing adhesion to metals and to adhesive cements is discussed in terms of a surface functional J. Mater. Res., Vol. 13, No. 5, May 1998
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