Three polyester films with different repeating units-poly(lactic acid) (PLA), poly(ethylene terephthalate) (PET), and poly(oxybenzoate-co-oxynaphthoate) (PBN)-were modified by plasma, and the way in which the chemical compositions of the polymer chains influenced the plasma modification was investigated with contact-angle measurements and X-ray photoelectron spectroscopy (XPS). There were large differences in the compensated rates of weight loss among the three polyester films when they were exposed to Ar and O 2 plasmas. The PLA film showed the highest rate for weight loss of the three films, and the PBN film showed the lowest rate. The PET and PBN film surfaces were modified to become more hydrophilic by either argon or oxygen plasma. However, the PLA film surface was not made more hydrophilic by the plasmas. XPS spectra showed that the PLA film surface was not modified in its chemical composition, but the PBN film surface was modified in its chemical composition to form COO groups in the PBN polymer chains. The reason that the PLA film surface was not modified but the PBN film surface was modified was examined.
ABSTRACT:The rf power was modulated (discharge on-time of 10 s and discharge off-time of 50 -500 s), for pulsed argon (Ar) and oxygen (O 2 ) plasmas used to irradiate PET film surfaces to modify the film surfaces. From data regarding the contact angle for the modified PET film surfaces and chemical analyses with XPS, effects of the rf power modulation on the surface modification are discussed. The pulsed Ar and O 2 plasmas are effective in modification of the PET film surface. There is no difference in the contact angle between the pulsed plasma and the continuous plasma. Furthermore, the pulsed Ar plasma is advantageous in formation of hydroxyl groups on the PET film surfaces. The rf power modulation has a possibility to modify into peculiar surfaces.
Effects of treatment using ammonia plasma on poly(lactic acid) (PLA), poly(ethylene terephthalate) (PET), and liquid-crystal polymer (LCP) were investigated to elucidate differences related to polymer structures and the mode of introduction of nitrogen functional groups onto the polyester surfaces. Nitrogen functional groups were introduced into PET and LCP, but were not introduced into PLA. Those results indicate reductions in the contact angle for PET and LCP. No decrease in the contact angle was observed for PLA. Reasons for differences in attachment of nitrogen functional groups by ammonia plasma processing on polyester surfaces were discussed. The respective actions of active species were investigated for radicals, electrons, and ions in plasma.
Surface modification of polymers by pulsed plasma has been investigated to minimize degradation reactions occurring at the same time as the surface modification reactions. The hydrogen radical, ion, and electron concentrations in the hydrogen plasma were simulated as a function of the elapsed time after turning off the discharge. The contact angle measurement showed that hydrogen plasma treatment, regardless of pulsed or continuous plasma, led to degradation reactions as well as defluorination and oxidation on PTFE surfaces. The degradation reactions of PTFE chains initiated by the pulsed hydrogen plasma were not as vigorous as those by the continuous hydrogen plasma. A combination of the on-time/off-time of 30/270s in the pulsed hydrogen plasma was efficacious in modifying PTFE surfaces.
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