Simultaneous and time resolved investigation of diffusion processes of individual model fuel components in acrylonitrile-butadiene-rubber in the light of swelling phenomena

Abstract

This work introduces a method allowing a simultaneous and time resolved tracing of diffusion processes of individual components of model fuel mixtures in elastomers using gas chromatography/mass spectrometry (GC/MS). Uptakes of dodecane and m-xylene, representing typical fuel components, were monitored in acrylonitrile-butadiene-rubber (NBR) specimens, which were stored in different mixtures of these two compounds. Calculations of individual diffusion coefficients and saturation concentrations of each substance show rising uptakes and diffusion rates of both constituents with increasing m-xylene content of the mixture. Additionally, sorption curves of dodecane were recorded for elastomers, which were pre-swollen in m-xylene or decalin. At the same time, the extraction of the pre-swelling agents was traced. Diffusion coefficients of dodecane were significantly higher compared to those found for the neat material.By immersing elastomers in binary mixtures containing different model fuel constituents, a relation between concentrations in the bulk fluid, individual swelling potentials of the mixtures' components and the attained equilibrium concentrations in the elastomer could be determined. In general, swelling potentials of mixtures are governed by the constituent with the highest individual swelling potential. Results from experiments involving model substances were interpreted in terms of the influence of a real fuels' composition on its swelling behavior towards elastomers contributing to a better understanding of diffusion processes.