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Effects of low-energy electron bombardment on the surface chemical structure and adhesive properties of polytetrafluoroethylene (PTFE)

Published online by Cambridge University Press:  31 January 2011

J.A. Kelber ,
J.W. Rogers Jr.  and
S.J. Ward
J.A. Kelber
Affiliation:
Sandia National Laboratories, Albuquerque, New Mexico 87185
J.W. Rogers Jr.
Affiliation:
Sandia National Laboratories, Albuquerque, New Mexico 87185
S.J. Ward
Affiliation:
Sandia National Laboratories, Albuquerque, New Mexico 87185
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Abstract

The x-ray photoemission studies of polytetrafluoroethylene (PTFE) bombarded by lowenergy electrons in ultra-high vacuum conditions indicate that the major chemical changes induced by electron bombardment are defluorination of the surface and cross-linking of the polymer chains. The same electron bombardment process, when performed in the presence of 1×10−6 Torr ND3, also results in the adsorption of nitrogen-containing groups at the surface. The rate of nitrogen adsorption is linear for short electron bombardment times while the rates of defluorination and cross-linking are roughly exponential. However, at long bombardment times, the rates of nitrogen uptake, defluorination, and cross-linking become zero at the same time, indicating that defluorination of the surface is the rate-determining step in electron beam-induced adsorption of nitrogen-containing species. Regardless of whether the bombardment is carried out in ultra-high vacuum or in the presence of ND3, the maximum modification depth is less than 30 Å. Pull tests performed on PTFE samples bombarded by electrons in ultra-high vacuum, then removed into air and bonded to epoxy show epoxy-PTFE joint strengths of 280–360 1b/in.2 (psi), are compared to zero psi for untreated PTFE and ≃2000 psi for cohesive failure within the PTFE layer.

Type
Articles
Information
Journal of Materials Research , Volume 1 , Issue 5 , October 1986 , pp. 717 - 723
Copyright
Copyright © Materials Research Society 1986

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References

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