Adhesion to Sodium Naphthalenide Treated Fluoropolymers Part I-Analytical Methodology

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Abstract
Fluoropolymers may be treated with sodium naphthalenide (Na/Naphth) in tetrahydrofuran (THF) so as to increase their ability to form adhesive bonds with other polymers or metals. We describe here a quantitative analysis of the chemical modification which results from such a treatment, using a range of derivatizations coupled with infrared (IR), ultraviolet (UV), and X-ray photoelectron (XPS) spectroscopic techniques. For example, after 60 min treatment of a perfluoroalkoxy film (PFA, a copolymer of tetrafluoroethylene and perfluoroalkylvinylether), the polymer was partially defluorinated to a depth of 115 nm, with almost all the carbons in the affected region being functionalized in some fashion. Carbonyl groups were present at about 3.3 × 10−9 equivalents per cm2 of film surface, which, averaged over the 115 nm affected depth, is equivalent to about 0.25 carbonyls per 100 carbons. The carbonyl content increased with increasing storage time in air. The other major functionalities were alkene (26 per 100 carbons), with a conjugation length of about 10, alkyne (18 per 100 C), aliphatic CH (3.5 per 100 C), hydroxyl (0.30 per 100 C), and carboxylic acid (<0.02 per 100 C). A comparison of the IR and XPS data shows that the unsaturation was distributed relatively uniformly through the 115 nm, while the carbonyl and hydroxyl species were concentrated in the top few nm.

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