Accelerated nitridation and oxidation by plasma on polyethylene

¹ Departamento de Física, Instituto Nacional de Investigaciones Nucleares, Apdo. Postal 18-1027, D.F., CP 11801, Mexico
² Departamento de Física, Universidad Autónoma Metropolitana Iztapalapa, Apdo. Postal 55-534, D.F., CP 09340, Mexico

Corresponding author: guillermo.cruz@inin.gob.mx

Received: 29 October 2008
Revised: 5 May 2009
Accepted: 26 August 2009
Published online: 30 October 2009

Abstract

Glow discharges of oxygen and nitrogen were applied to low density polyethylene thin films in order to study accelerated oxidation and nitridation in the polymer. The studies were focused on the morphologic, crystalline and hydrophilic evolution promoted by plasma exposure. The particular chemical characteristics of the gases and the constant impact of high-energy particles on the surfaces produced different types of erosion. Oxygen plasmas produced the release of fragments from the polymeric surface which created fibered textures and nitrogen plasmas resulted in folded morphologies of nano and micro dimensions on polyethylene. The plasmas of both gases increased and decreased the crystallinity in the polymers, between 33% and 57%, with similar tendencies, differing only in the percentage of crystallinity. The plasma exposure produced a decrease in the contact angles of water on polyethylene in the first 30 min of plasma, from 70% in the untreated polymers, to 45% and 35% as a consequence of the polar groups added to the surface.