Effect of Preliminary Heating of a Polymeric Polytetrafluoroethylene Target on its Ablation by a Continuous CO2 Laser

We study experimentally the effect of pre-heating polytetrafluoroethylene (PTFE) on its laser ablation rate from a continuous wave CO2 laser. The ablation rate and the fraction of fiber formed grow significantly as the initial temperature of the polymeric target increases from 292 to 683 K. The ablation rate obeys two exponential dependences on the temperature with different apparent activation energies for the high-temperature and low-temperature regimes. We find that a crossover temperature of 460 K correlates best with the temperature for sol-gel transformation in the bulk. The faster rates at higher temperature are due to the ability of the reactive species generated in the ablation process to react with more of the system.