Conversion of an industrial LIBS system to double-pulse operation to improve sulphur detection in rubber-based parts

Abstract

The detection of sulphur as an elementary component of the crosslinking system of rubber compounds is difficult in LIBS single-pulse operation due to the usually low concentration and the poor response behavior of the analyte. However, reliable proof of the distribution quality of sulphur in the compound is a decisive quality criterion for the homogeneity of the crosslinking density achievable during vulcanization, which is important for the uniform performance of an elastomeric article, especially under dynamic load.Therefore a commercially available industrial LIBS system, (1064 nm Nd:YAG solid state laser, 100 mJ, 20 Hz) is extended with a 266 nm laser (Nd:YAG solid state laser, 60 mJ, 20 Hz) to combine an UV-based initial excitation (for ablation efficiency) followed by an IR-pulse (to realize highest plasma heating) to improve sulphur detection in rubber based compounds and parts. Optimization of the system parameters are investigated to improve the ablation efficiency and to increase the measured signal intensity/signal-to-noise-ratio of the analyte. The VUV sulphur lines at 180.658, 181.956, and 182.561 nm and the NIR sulphur lines at 921.298, 922.823, and 923.751 nm are under investigation.