with the selected treatment gas by selectively opening one of the valves 20 22 25 and thereafter evacuating the chamber the treatment gas then fills the chamber under 0 2 0 7 torr absolute pressure the treatment gas within the chamber is at a relatively low concentration in the range of 1 u00d7 10 5 to 4 u00d7 10 5 gram moles per liter the power supplied by transformer 19 is then increased at the given gas pressure to cause an electrical discharge typically the required power will range from 10 to several hundred watts the resulting ionized gas becomes the reactive medium by varying the drive speed of film 14 through the treatment chamber 11 the exposure time of the film to the plasma can be varied from a few seconds to several minutes thus providing a convenient means for varying the treatment level thermal degredation of the polymeric film is prevented because the plasma reaction is carried out at low temperature e g about 50 u00b0 120 u00b0 celsius due to the reduced gas pressure 0 2 to 0 7 torr and the use of a low concentration 1 u00d7 10 5 to 4 u00d7 10 5 gram moles per liter of ionized gas the plasma gas can be inorganic or organic compounds as examples of.