PULSE-DEPENDENT AND TIME-DEPENDENT OBSERVATION OF UV-LASER-INDUCED STRUCTURES ON POLYMER SURFACES

Irradiation of highly absorbing polymers with a pulsed excimer laser can change the surface topography under certain conditions. Fibres made of poly(ethylene terephthalate) and polyamide show a characteristic roll-like morphology after treatment with 193 or 248 nm laser irradiation, which promises interesting applications in industrial processing of textile fibres. For a systematic study of the influences of the various parameters monofilaments made of poly(ethylene terephthalate) and poly(propylene) were irradiated in place in a microscope. This allowed the observation of the evolution of the structure shot by shot. Quantitative data were taken by use of an image analysing system. The study was done with various laser fluences, wavelengths and in dependence on mechanical stress (draw) on the sample. With increasing number of shots the morphology gets more coarse due to a sort of "combining" of the rolls showing a logarithmic dependence of the mean roll-distance on the number of pulses applied. Characteristically, the fibre decomposes into ellipsoidal pieces after a sufficient number of shots. The polyolefinic material cannot be modified directly with 193 or 248 nm laser radiation due to the low absorption coefficient for these wavelengths. By using a 157 nm F2 laser certain surface modifications were observed on fibres and films. The structures were similar to the effects previously found on poly(ethylene terephthalate).