Chemical Reaction Between Polymers (Pc, Pmma, and Pet) and Oxygen Gas During Ar + Irradiation
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. Res. Soc. Symp. Proc. Vol. 396 0 1996 Materials Research Society
EXPERIMENT Commercial PC (polycarbonate), PMMA (polymethylmethacrylate), and PET (polyethylene terephthalate) sheets were cut into 10 x 10 mm2 , cleaned in the ultra sonic bath of methanol for 30 min, and dried in the oven at 60 * for 30 min. Irradiation of the samples was carried out by a cold-hollow cathode ion gun (5 cm diameter) purchased from Russia in the vacuum chamber maintaining about 2 x 10-4 torr. Argon gas was injected into the ion gun at a constant flow rate (3 ml/min) to produce Ar÷ ion beam. Oxygen as an environmental gas was blown onto the polymer surfaces at a flow rate of 0 and 6 ml/min during the irradiation. The energy of Ar+ was set at I keV and irradiation fluences were varied from 1014 to 1017 ions/cm 2 as measured by a Faraday cup. The detailed experimental scheme was presented in the previous report [8]. The wettability of the samples was determined by measuring the contact angle of distilled water droplets (0.025 nt) on the sample surface at room temperature, using a contact anglemeter (ELMA, Goniometer. Model G- 1). The measurements were made at four different locations of each sample. An XPS (Surface Science Instrument, Model 2803-S) was used to analyze the changes in the composition and chemical bonds of the polymer surfaces before and after Ar+ beam irradiation. The analysis was performed in a high vacuum chamber (base pressure: 2 x 10-10 torr) using Al (K,,), X-ray (hv = 1486.6 eV), X-ray monochromator and a concentric hemispherical analyzer with a resolution of 0.48 eV. Take-off angle was set at 30 ° and the binding energies of carbon and oxygen of samples were measured immediately after treatment. The measured binding energies were corrected by taking the binding energy (284.6 eV) of Cls in C-C group as a reference. Peak ratio (O/C) was calculated by comparing the peak area of each component. RESULTS AND DISCUSSION 1. Contact angle measurements 90 803
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Ion Dose ( ions /cm ) Fig. 1 Contact angle of water on PC, PMMA and PET irradiated with and without oxygen environment as a function of ion dose Contact angle measurements of water droplets on the polymers provides the information on
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the hydrophilicity or hydrophobicity of the polymers as well as their surface tensions. It is a well known fact that the lower the contact angle of water on a polymer, the higher hydrophilicity the polymer has. Figure 1 shows the static contact angles of water on PC, PMMA and PET irradiated with and without oxygen environment at various ion doses from 1014 to 10 ". All of the samples show the similar behavior of wettability. When the samples were Ar+ irradiated without oxygen, the contact angle of water decreased and remained almost constant with increasing ion dose as shown in Figure 1. This may be due to the increase in the surface roughness caused by irradiation [9]. Others also repor
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