Surface Fluorination of Carboxylated Nitrile Butadiene Rubber: An XPS Study

Abstract

Because of their exceptional reactivity, fluorine and fluorinated gases are of primary importance for the modification of the surface properties of materials. This study is devoted to surface treatment of thin nitrile gloves, made of carboxylated nitrile butadiene rubber latex, using either direct fluorination (10% F₂gas diluted in N₂) or plasma-enhanced fluorination in radio-frequency cold plasmas using fluorinated gases (CF₄, CHF₃). Mechanisms of fluorination of these co-elastomers have been proposed on the basis of the assignment of the different components of the XPS spectra. Several mechanisms have been observed depending on the fluorination conditions. Although the modification of nitrile gloves is already effective for fluorination reactions at room temperature, an important activation is observed for experiments carried out at 90°C. When the treatments are carried out at room temperature, a gradual fluorination occurs: in the case of 10% diluted F₂ gas, monofluorinated C—F groups are the species most found at the surface and perfluoro groups CF _n are present in lower amount. An addition reaction takes place at the $\rlap{--} ($CH=CH$\rlap{--} )$ double bonds of the polybutadiene entities, leading to $\rlap{--} ($CHF=CHF$\rlap{--} )$ units. Whatever the fluorination method, thermal activation yields a more massive fluorination of the surface that finally leads to perfluorinated $\rlap{--} ($CF₂ $\rlap{--} )$ groups and terminal —CF₃ groups.