ACTIVATION OF POLYMER POLYETHYLENE TEREPHTHALATE (PET) BY EXPOSURE TO CO2 AND O2 PLASMA

A comparison of O-2 and CO2 plasma treatment for the functionalization of PET (polyethylene terephthalate) is presented. The plasm was created in a glass discharge chamber at a pressure of 75 Pa by an electrodeless RF discharge. The RF generator operated at a frequency of 27.12 MHz and a power of about 200 W. The samples were cut into small pieces and exposed to plasma. for different periods. Immediately after the treatment the samples were characterized by high-resolution XPS. A comparison of both survey and high-resolution Cls peaks revealed that the amount of the specific functional groups formed on the surface during the plasma treatment was the same for the CO2 and O-2 plasma. Within the limits of the experimental error the concenteration of hydroxyl groups was about 34 % and carboxyl groups was about 29 % for a sample treated in both plasmas for 30 s. The results were explained by the rapid dissociation of both molecules to neutral oxygen atoms that are fairly stable in glass discharge tubes and readily react with the surface of polymer materials. Any effect of CO radicals is neglected since oxygen atoms are chemically more reactive, so possible differences in the surface functionalization might have been observed only for extremely short treatment times and/or orders of magnitude lower pressure.