Dynamics of the evolution of volatile products during laser‐induced polymer destruction

Abstract

The dynamics of evolution of volatile products arising during destruction of poly(viny1 alcohol) and polyacrylnitrile films under the action of cw laser radiation were investigated by means of time-of-flight mass spectrometry. It was found that the evolution of volatiles occurs in two stages, one isothermal and the other nonisothermal. Depending on laser focusing and power, the nonisothermal stage comprises three dynamic regimes of desorption of volatile products: regime of single ejection, oscillating regime and chaotic behaviour of evolution. It is shown that the various regimes of desorption are due to inhomogeneity of laser heating and nonuniform propagation of the destruction wave from the centre of the laser beam to the periphery. 0 1992, HUthig & Wepf Verlag, Basel CCC 0025-1 16X/92/$05.00

Interplay between Chemical, Thermal, and Mechanical Processes Occurring upon Laser Excitation of Poly(methyl methacrylate) and Its Role in Ablation

“…The ejection in these cases therefore is determined to be based on chemical destruction, due to the role played by gaseous species in hollowing out the polymer matrix and causing the ejection of chunks of polymer substrate. This mechanism is similar to that for pure photochemical cases in the previous set of runs, where ejection was described using a two-step model by Kalontarov and Marupov . Similarly, the second ejection in the heating case, all of the ejections for the Norrish type I case and the Norrish type II case, are judged to originate largely via a chemical disintegration pathway as seen in Figure e,f.…”

“…Both of these types of models fail to account for subsequent chemical reactivity of the disintegrated polymer substrates. This reactivity has been shown to play an important role in ablation of many polymers. ,,, A model by Kalontarov considers ablation as a coupled two step process with chemical damage followed by thermally activated ejection. However, the thermal destruction of the polymers cannot be ignored especially at the high fluences where high temperatures and stresses may prevail. ,,,,− Similarly, the influence of mechanical stresses on thermal and chemical processes and their interaction have been largely ignored in modeling efforts despite direct evidence of their presence in the sample. ,, …”

“…This reactivity has been shown to play an important role in ablation of many polymers. 14,18,27,32 A model by Kalontarov 56 considers ablation as a coupled two step process with chemical damage followed by thermally activated ejection. However, the thermal destruction of the polymers cannot be ignored especially at the high fluences where high temperatures and stresses may prevail.…”

On the role of chemical reactions in initiating ultraviolet laser ablation in poly(methyl methacrylate)

“…Following the removal, the laser interacts with a fresh polymer substrate deeper in the sample, and the process continues. The variation of the concentration c of photoproducts ͑i.e., transformed material͒ in the reaction volume was given by 62 dc dt…”

Laser-Induced Dissociation of an Energetic Polymer: A Spectroscopic Study of the Gaseous Products

“…The details of the ablation mechanism are still a matter of debate; both photochemical and thermal processes and several photothermal mechanisms were suggested in the literature. [7][8][9][10] A visible luminescent plume often accompanies the ablation of solid materials, as has been shown by several groups. Dyer et al 5 reported that in the case of polyimides, the main emission bands are due to CN and C 2 .…”