Plates of polyethylene with ultrahigh molecular weight (PEUHMW) were treated by radiofrequency capacitive CF4 plasma discharge in order to incorporate fluorinated functional groups. The consequences of subsequent heating treatments after fluorination were investigated by the combined use of angle‐resolved XPS characterizations and measurements of surface free energy γs . The temperature range explored covers the zone from room temperature to 240 °C. After the CF4 plasma treatments, the incorporation of CF x groups at the surface of PEUHMW induces a decrease of the γs value. Further thermal treatments lead to modifications of the chemical surface composition and of γ s . The most important changes concern a significant increase of the surface free energy, where the contribution of the dispersive component is the most affected, and a decrease of the F/C ratio. The fluorine departure is caused by chain scission in the polymer and is accompanied by a surface oxidation, as revealed by the O 1s peak intensity increase. Copyright © 1999 John Wiley & Sons, Ltd.

The 915 MHz band wavelength is convenient for high power flowing plasma generation, especially in N 2 for nitrogen atom production, at low power density through large sections and gas high residence times. The chosen TM 110 mode cavity when unloaded theoretically fulfills such requirements. Its qualification at power up to 2.5 kW shows a good power transfer when running with flowing nitrogen in the pressure range 150-1330 Pa. Thermal measurements made on the liquid cooling the discharge tube point out a constant power ratio (70%) released by the plasma in the form of heat. A discharge length of about 2/3 times the cavity length is deduced from the optical N 2 (C 3 u ) and N + 2 (B 2 + u ) emission intensities. The axial profiles of the vibrational and rotational temperatures of N 2 (C 3 n ) are presented and discussed with regard to the existence of strong radial gradients and possible excitation mechanisms. The N( 4 S) concentration generated by this plasma source is compared at a 1.5 kW power with that of a 2450 MHz TM 012 cylindrical cavity in the far remote afterglow. Finally about 3.3% of the absorbed power is transformed into dissociation with a power density less than 1 W cm −3 , allowing power increases within factors much larger than ten.