Quantification of sulfur distribution on rubber surfaces by means of μ-X-ray fluorescence analysis

A homogeneous distribution of sulfur in a rubber compound is often desired. Spatially resolved imaging tech-niques are useful for evaluating the distribution of this crosslinking chemical. Typical measurement methods such as SEM (scanning electron microscopy) or TEM (transmission electron microscopy) have very high reso-lutions. However, the sample size or the maximum area to be investigated is limited, which makes it difficult to obtain a statistically reliable determination of sulfur homogeneity across the component or sample.In this work, an alternative measurement technique is therefore presented: the mu-XRF (mu-X-ray fluorescence analysis). With the help of this method, it is possible to scan surfaces of several cm(2) and to show the distribution of different chemical elements. Its measuring principle has been known for decades but has hardly been used in the rubber industry so far.The main reason for this is that its quantification process for polymeric samples is more complex than for geologic or metallic samples, which are typically been investigated with mu-XRF to date. In this paper, this issue is addressed and a solution is presented: With the help of the fundamental parameter method, the determination of sulfur homogeneity and distribution on rubber surfaces becomes possible. This opens up a variety of further possibilities for the use of mu-XRF in the rubber industry: For example, it could be used in areas of tire production, recycling of end-of-life rubber, and beyond.

Automated summary

This article presents an alternative measurement technique, mu-XRF (mu-X-ray fluorescence analysis), for evaluating the homogeneous distribution of sulfur in rubber compounds. By using the fundamental parameter method, the distribution of sulfur on rubber surfaces can be determined. This technique overcomes the limitations of traditional methods in obtaining statistically reliable sulfur homogeneity measurements and has potential applications in the rubber industry.