Quantitative characterisation of capillary extrusion flow instabilities based on laser scanning: Study of the influence of silane coupling agent on ESBR/BR

ABSTRACT In this paper, three-dimensional (3D) laser confocal microscopy has been utilised to quantify the flow instability during the capillary extrusion of ESBR/BR compounds with different silane coupling agent TESPD dosage and processing conditions. This approach aims to address the challenge of flow instability characterisation during extrusion. The analysis of the relationship between compound structure and extrusion rheological behaviours revealed that the introduction of TESPD markedly improved silica dispersion within the rubber matrix. Furthermore, the silanization reaction was found to be promoted by extending the mixing duration by two minutes. The comparative analysis of the flow instability characteristics of large-area samples, utilising data derived from spatial particle positions through 3D laser confocal microscopy imaging, elucidated the pivotal role of TESPD in augmenting flow stability and mitigating distortion in capillary extrusion processes. The frequency of flow instability occurrence and the degree of distortion were quantitatively characterised by means of Fourier-transform spatio-temporal maps. The results indicated that the incorporation of TESPD significantly reduced the distortion of capillary extrudates. At a shear rate of 10 s -1 , it exhibited reductions of 60.51% in SD and 73.16% in amplitude relative to the sample without TESPD. The extrudate roughness and die swelling ratio analysis further substantiates the mitigating effect of TESPD on flow instability.