About The Deterioration Of Polyethylene Exposed To Plasma Discharges: A Comparison Between Two Models

The present work is devoted to the modelling of the deterioration process of polyethylene exposed to reactive plasma. In particular, we present the comparison between two different models. The first one, already presented in the literature, considers the H-abstractions due to the OH. and O. radicals, and some successive reactions, involving mainly other gaseous species. The second model, in addition to the first model reactions, is enriched by including the effects (both H-abstractions and chemisorptions) due to the collisions of a series of plasma ions with the surface. These collisions have been reproduced by ab initio molecular dynamics simulations. The performance of both models has been tested by implementing them in a code for simulation of surface chemical reactions induced by a plasma discharge. The related results are then compared with some experimental data. The first model is able to well reproduce the experimentally detected oxidation of the polyethylene surface exposed to plasma discharges. The second model, including also the decisive effects of the NO. radical on an already oxidized surface, is able to explain the presence of nitrogen on the sample surface.