Analysis of polyethylene surface sulfonation

Attachment of SO 3 H groups onto the surface of polymers by treatment with fuming sulfuric acid is a well‐known procedure. In the present study we compare the number of SO 3 H groups per unit area measured by a number of methods including weight gain, thickness, FT‐IR transmittance spectra, FT‐IR surface spectra with ATR method, sodium exchange, and p H measurement of water in contact with the polymer surface. It can be shown that, under the chosen conditions, i.e., room temperature and 32% SO 3 in H 2 SO 4 , oxidation of PE is the main reaction, while sulfonation accounts for less than 20% of the weight gained during reaction. Differences in the reactivity of high density and low density polyethylenes are discussed. Deprotonation in water compared with H + /Na + exchange indicates a poor penetration of sodium ions into deeper layers of the polymer.