Mass spectroscopy and ablation characteristics of nylon 6.6 in the ultraviolet

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 th e ArF and KrF excimer lasers. The characteristic parameters of the laser ab lative process, such as etch rate at different fluences, the threshold flue nce, and the absorption coefficient for both wavelengths were determined. E ven at low laser energy, there was a complete breaking of the polymeric cha in bonds. The following photofragments were observed at 248 nm: H, H-2, C, CH, CH2, N, NH, O, OH, H2O, C2H, C2H2, CN, C2H3, HCN, N-2, CO, C2H4, COH, C 2H5, N2H, NO, C2H6, H2CO, N2H2, C-2, CH2NH, O-2, C3H3, C3H4, C3H5, C3H6, CN O, HCNO, and H2CNO. At 193 nm no photofragments were observed for m/e large r than 30 amu. The photofragments with two carbon atoms have a relatively h igher probability to be dissociated from the parent monomer, than heavier p hotofragments with four carbon atoms. The mass spectroscopic studies and th e absorption spectrum of nylon 6.6 in the ultraviolet, suggest photochemica l bond-breaking at 248 and 193 nm. The monomer dissociates into fragments w ith the predominant mass at 28 amu for both laser wavelengths. Therefore th e amide group is mainly involved in the photodissociation process of nylon 6.6 in the ultraviolet. The experimental results suggest that the photochem ical dissociation of the polymeric chain is the dominant mechanism of the l aser ablation of nylon 6.6 at 193 and 248 nm.