Laser ablation of UHMWPE-polyethylene by 438 nm high energy pulsed laser

Pulsed laser ablation of ultra-high-molecular-weight-polyethylene (UHMWPE) is investigated at Prague Asterix Laser System (PALS) Laboratory. The high ablation yield as a function of laser energy is presented at 438 nm laser wavelength. The mechanisms of the polymer ablation are studied on the base of ‘‘in situ’’ analysis, such as mass quadrupole spectrometry and time-of-flight measurements, and ‘‘ex situ’’ analysis, such as SEM investigations and Raman spectroscopy. Results show that the laser irradiation induces a strong polymer dehydrogenation and molecular emission due to different CxHy groups having high kinetic energy and high charge state. At a laser pulse energy of 150 J the Hþ, Cnþ ions (n ¼ 1 to 6) are emitted from the plasma with velocities of the order of 108 cm/s, while the CxHy groups and the carbon clusters, detected up to C16, have a velocity about one or two order magnitude lower. The laser ablation process produces a deep crater in the polymer, which depth depends on the laser pulse energy and it is of the order of 500 mm. The crater volume increases with the laser pulse energy. Results demonstrated that the laser radiation modifies the polymer chains because dehydrogenated material and carbon-like structures are detected in the crater walls and in the bottom of the crater, respectively. A comparison of the experimental results with the data available in literature is presented and discussed.