Effect of mixing technique on structure and properties of styrene-butadiene-styrene block copolymer/carbon nanotube composites

A comparative investigation was conducted to evaluate the impact of mixing technique (twin-roll milling, internal mixing, and the masterbatch method) on the structure, mechanical properties, thermal stability, electrical conductivity, and thermal conductivity of styrene-butadiene-styrene block copolymer (SBS)/carbon nanotube (CNT) composites. It was found that the incorporation of CNTs enhanced the mechanical, electrical, and thermal conductivity properties of the composites, with negligible effects on thermal stability. The choice of processing method had a pronounced influence on performance, with the samples prepared by twin-roll mixing exhibiting the best properties, while those produced via direct internal mixing demonstrated the lowest performance. Unexpectedly, the masterbatch method did not present advantage in any of the tested performances. Scanning electron microscopy analysis confirmed that CNT dispersion was most uniform in the twin-roll mixed samples. In contrast, large CNT agglomerates were observed in the internal mixed samples. The masterbatch group presented small CNT aggregates, which were produced by breaking the large agglomerates in the masterbatch. Dynamic mechanical analysis indicated that the interfacial interactions between CNTs and SBS were not significantly altered by different processing techniques. Therefore, the performance variations were primarily attributed to differences in CNT dispersion states. These findings present an effective approach for fabricating cost-efficient, high-performance CNT-reinforced elastomer composites and offer valuable insights for practical industrial applications.