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Model of laser-induced Material Removal of Polymers and Gasdynamics

: Aden, M.; Wesner, D.A.; Kreutz, E.W.; Poprawe, R.

Phipps, C.R. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
High-power laser ablation
Bellingham, Wash.: SPIE, 1998 (SPIE Proceedings Series 3343)
ISBN: 0-8194-2790-X
S.505-514 : Ill., Lit.
Santa Fe High Power Laser Ablation Conference <1998, Santa Fe/N.Mex.>
Fraunhofer ILT ()
polymer; laser radiation; Euler equations; degradation; stoichiometry

A model is build up to describe the effects of the laser-induced material removal of polymers and the dynamics of the volatile species. The heating and removal are described by the volume- heating of the irradiated polymer due to the absorption of laser radiation within the optical penetration depth and a phase transition from the condensed to the gas state of the polymer. The delivered energy due to the absorption of laser radiation is distributed to the different channels of decomposition in accordance to the temperature. The dynamics of the volatile species is calculated by the use of the Euler equations (non-dissipative continuum mechanical equations of the conservation laws of mass, momentum and energy). The flow field pattern of the gas phase (density, velocity and pressure) during the material removal of PE, PP and PMMA exceeds the one of PE, which exceeds the one of PP. This is attributed to the optical penetration depth of the three polymers. The depth of material removal increasing fluence this effect is strongest for PP followed by PE and smallest for PMMA.