Mass spectroscopy and ablation characteristics of nylon 6.6 in the ultraviolet
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We report on the mass spectroscopic and the laser ablative characteristics of nylon 6.6 [-NH-(CH2)6-NH-CO-(-CH2)4-CO-] at 193 and 248 nm, using the ArF and KrF excimer lasers. The characteristic parameters of the laser ablative process, such as etch rate at different fluences, the threshold fluence, and the absorption coefficient for both wavelengths were determined. Even at low laser energy, there was a complete breaking of the polymeric chain bonds. The following photofragments were observed at 248 nm: H, H2, C, CH, CH2, N, NH, O, OH, H2O, C2H, C2H2, CN, C2H3, HCN, N2, CO, C2H4, COH, C2H5, N2H, NO, C2H6, H2CO, N2H2, C2, CH2NH, O2, C3H3, C3H4, C3H5, C3H6, CNO, HCNO, and H2CNO. At 193 nm no photofragments were observed for m/e larger than 30 amu. The photofragments with two carbon atoms have a relatively higher probability to be dissociated from the parent monomer, than heavier photofragments with four carbon atoms. The mass spectroscopic studies and the absorption spectrum of nylon 6.6 in the ultraviolet, suggest photochemical bond-breaking at 248 and 193 nm. The monomer dissociates into fragments with the predominant mass at 28 amu for both laser wavelengths. Therefore the amide group is mainly involved in the photodissociation process of nylon 6.6 in the ultraviolet. The experimental results suggest that the photochemical dissociation of the polymeric chain is the dominant mechanism of the laser ablation of nylon 6.6 at 193 and 248 nm.
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