| AVS 56th International Symposium & Exhibition | |
| Advanced Surface Engineering | Monday Sessions |
| Session SE-MoA |
| Session: | Atmospheric Pressure Plasmas |
| Presenter: | E. Gonzalez, University of California, Los Angeles |
| Authors: | E. Gonzalez, University of California, Los Angeles M. Barankin, University of California, Los Angeles P. Guschl, Surfx Technologies, LLC R. Hicks, University of California, Los Angeles |
| Correspondent: | Click to Email |
An atmospheric pressure oxygen and helium plasma was used to activate the surfaces of polyethylene (PE) and polymethyl methacrylate (PMMA). The plasma physics and chemistry was investigated by numerical modeling. It was shown that as the electron density of the plasma increased from 3x1010 to 1x1012 cm-3, the concentration of O atoms and metastable oxygen (1∆gO2) molecules in the afterglow increased from 6x1015 to 1x1017 cm-3, while the concentration of ozone decreased from 5x1015 to 2x1015 cm-3. The oxygen atoms, metastable oxygen (1∆g O2) molecules and ozone were the principle reactive species present in the afterglow. Exposing the polymers to the plasma afterglow for up to 30 seconds led to surface activation and an increase in bond strength of the polymers to adhesives by as much as 16 times. X-ray photoelectron spectroscopy of PMMA revealed an 8% increase in the C 1s peak area attributed to carboxylic acid groups (288.9 eV). In addition, the C 1s peak due to the methyl pendant groups (285.0 eV) decreased by 5%. The O:C ratio of PMMA increased from 0.4 to 0.7 after plasma treatment. Surface analysis of the polymers by internal reflection infrared spectroscopy confirmed the presence of carboxylic acid groups at 1710 cm-1 and hydroxyl groups at 3100 to 3500 cm-1 after activation. These results indicate that oxygen atoms and metastable O2 molecules generated in the plasma rapidly oxidize the polymer chains. The experimental results as well as a detailed description of the reaction mechanism will be presented at the meeting.