Infrared laser ablation of poly(vinylidene fluoride): The Loss of HF

Abstract

The mechanism and kinetics of infrared laser ablation of poly(vinylidene fluoride) (PVDF) in vacuum have been investigated to understand how this can be used as a polymer processing technology. The laser heats the surface and initiates decomposition of macromolecules in the molten polymer layer which rapidly leads to production of an ablative flow of polymer decomposition products. There is only a short induction period of up to 2 s before ablation begins. After the initial period, the rate of mass loss increases linearly with the time of laser exposure. Spherical particles with an average diameter of about 100 nm are formed on the surface of the powder coating obtained by laser ablation. The particle distribution ranges from 50 nm to 300 nm. The main gaseous product of ablation is HF from dehydrofluorination. A seccond important ablation process is the formation of gaseous carbenes generated during secondary reactions. Proposed ablation reactions due to laser-induced thermal dehydrofluorination occur in two stages. In the first stage, a double bond appears in PVDF due to direct loss of HF. Subsequent detachment of HF leads to the appearance of both triple bonds and cumulene bonds.