Influence of neutral and charged species on the plasma degradation of the stearic acid

in this work, stearic acid (sa) was degraded in an ar-o2and ar-h2post-discharge environment created by a plasma reactor with a microwave source and in an ar, ar-h2and ar-o2dc (direct current) discharge environment created in a cathode-anode confined system. the afterglow region is useful for understanding the role of the chemically active species (o, o2, h and h2). in contrast, the discharge region allows the observation of the effects of chemically active species, charged species (ions and electrons) and photons. the influence of these species on the grafting and etching of sa was evaluated by measuring the mass variation, mass variation rate and chemical composition. the results showed that when only chemically active oxygen species are present, the sa is preferentially grafted. however, when both photons and charged species are present, the sa is more efficiently etched. when the ar-h2and ar environments are utilized; the sa is not efficiently degraded.