An XPS investigation of the radiation induced degradation reactions of cellulose nitrate: Part 1-Argon plasma induced surface reactions

Abstract

Some surface aspects of the argon plasma induced degradation reactions of cellulose nitrate have been investigated by X-ray Photoelectron Spectroscopy (XPS). It is shown that plasma treatment results in an initial decrease in the surface nitrogen and oxygen concentrations, the creation of highly oxidized carbon environments (as observed by a broadening in the C1s spectra of the treated materials) and the creation of new 'reduced' nitrogen functionalities (which appear at lower binding energies [398-402 eV]). Whilst little change is noted in the surface nitrogen and oxygen concentrations after the first minute of treatment, plasma irradiation continues to produce changes in the C1s and N1s core level spectra. In the N1s core level there is a slow but continued conversion of nitrate esters to the new nitrogen functionalities. However, the rate of this conversion is much faster in the first minute of irradiation than afterwards and consequently even after 40-min plasma treatment there is still a significant concentration of nitrate esters remaining in the top 50 Å of the treated materials. The observed changes in surface chemistry of cellulose nitrate with plasma treatment are correlated with the depth to which direct and indirect energy transfer processes are known to induce degradation in polymers. © 1991.