The surfaces of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) were treated with an atmospheric-pressure oxygen and helium plasma. Changes in the energy, adhesion, and chemical composition of the surfaces were determined by contact angle measurements, mechanical pull tests, and X-ray photoelectron spectroscopy (XPS). Surface-energy calculations revealed that after plasma treatment the polarity of PET and PEN increased 6 and 10 times, respectively. In addition, adhesive bond strengths were enhanced by up to 7 times. For PET and PEN, XPS revealed an 18-29% decrease in the area of the C 1s peak at 285 eV, which is attributable to the aromatic carbon atoms. The C 1s peak area due to ester carbon atoms increased by 11 and 24% for PET and PEN, respectively, while the C 1s peak area resulting from C-O species increased by about 5% for both polymers. These results indicate that oxygen atoms generated in the plasma rapidly oxidize the aromatic rings on the polymer chains. The Langmuir adsorption rate constants for oxidizing the polymer surfaces were 15.6 and 4.6 s(-1) for PET and PEN, respectively.

An atmospheric pressure capacitive discharge source has been developed that operates at power densities over 100 W cm −3. The ground state nitrogen atom concentration was measured at the exit of the source by titration with NO, and it was found to reach a maximum of 3.0 ± 0.8 × 10 17 cm −3 at 6.0 vol% N 2 in argon, 250 • C and 150 W cm −3. This is equivalent to 2.3 vol% of N atoms in the afterglow. At these conditions, the electron density and temperature are estimated to be 3.1 × 10 12 cm −3 and 1.2 eV. A plug-flow model of the plasma and afterglow was developed, and it was determined that the maximum N atom concentration achievable is limited by three body recombination.

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