The photochemical reaction process steps in substituting the functional groups on the surface of fluorocarbon [FEP] by irradiating an Xe2 excimer lamp on water or formic acid and FEP placed on the attenuated total reflectance [ATR] prism, has been measured in real time. These steps include, water photo-dissociation, the defluorination of the FEP and the hydrophilic group substitution.
In case of formic acid, the absorption peaks of the -CHO in the region of 2940 cm−1 and the -COOH in the region of 1710 cm−1 decreased respectively by photo dissociation, but that of the -OH in the region of 3300cm−1 increased. The results indicated that the -CHO and -COOH have turned to -OH.
Furthermore, the contact angle with water was measured. When compared to the untreated sample, whose contact angle was 110 degrees, the contact angle of the sample treated with water and the Xe2 lamp irradiation for 25 minutes became 31 degrees, and that of the sample modified with formic acid and the lamp irradiated for 25 minutes further improved to 17 degrees. This implies that the hydrophilic groups were produced more in formic acid than in water.