Surface structuring of poly(ethylene terephthalate) by UV excimer laser

The direct irradiation of poly(ethylene terephthalate) (PET) with KrF excimer laser 248 nm was imaged and studied using atomic force microscopy (AFM). AFM was used to follow the morphological changes caused by subsequent laser pulses on the same area of the irradiated PET samples. AFM also provided quantitative data on the laser-induced surface and allowed three-dimensional imaging of non-conducting surfaces. The images revealed by AFM are not available so far with other imaging techniques. Changes in the surface morphology of PET fibres were found in relation to the laser energy applied. The mean roll-to-roll distance increased with increase in the laser energy. The merging of ripples was observed and was believed to be a major reason for increased roll-to-roll distance. With approximately 200 pulses (which depends on the materials and the laser fluence), the ripples almost approached parallelism. No further change of the PET surface was observed with more laser pulses applied, since the fibre had disintegrated into “ellipsoidal segments”. Meander-like structures superimposed onto the top of the ripples were observed. The wetting behaviour of PET due to laser treatment was also studied by employing the contact angle method.