Ablation of polytetrafluoroethylene using a continuous CO₂ laser beam

The ablation of polytetrafluoroethylene (PTFE) is studied using a continuous CO₂ laser beam of 30–50 W at a mean intensity of 0.05–50 MW m⁻². The ablation products and changes in the target layer are examined using infrared spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction and electron microscopy. The main experiments were conducted with an unfocused beam of intensity 0.9–1.2 MW m⁻². The radiation–polymer interaction characteristics were found to change appreciably as the ablation conditions are approached. Within the polymer layer, light scattering diminishes and true resonant light absorption increases. Two distinct polymer components, which differ primarily in their resistance to CO₂ laser radiation, were found to exist under ablation conditions. The less stable component depolymerizes intensively, while the more resistant component is blown up into fibres by intense gas flow. The reasons behind this behaviour are discussed. Preliminary gamma irradiation of PTFE is found to have a significant influence on the laser ablation process.