Plasma processing of PET in an oxygen decoupled plasma source

Samples of poly(ethylene terepthalate) (PET), 200 mm, were exposed to an energetic oxygen discharge from a decoupled plasma source, in order to modify local surface properties. Samples were placed at two distances, 13 cm and 20 cm, from the top of the discharge coil to assess the interaction between the sample and the DPS discharge. The discharge was generated at 13.56 MHz in oxygen at varying pressures of 100 -1000 mtorr at applied power levels of 250 - 1000 watts. Optical emission spectroscopy (OES) from 250 nm - 900 nm was used to characterize the interaction between the oxygen discharge and the samples during processing. Atomic species of oxygen decreased and molecular species of OH and CO increased during processing, particularly with increased applied power and pressure. Surface modification was monitored using the sessile drop method. The samples showed a reduction in contact angle indicating a change from a hydrophobic condition to a hydrophilic condition with processing. Visible changes were also seen in the samples ranging from a light roughening of the surfaces at lower applied power levels to distortion and melting of the samples at applied power levels of 750 and 1000 watts, with more damage occurring at the closest distance to the discharge.