Enhancing properties of natural rubber nanocomposites with hybrid fillers and ionic liquid

Abstract

Natural rubber (NR) nanocomposites were prepared by incorporating carbon nanotubes (CNTs), CNT/silver nanoparticles (AgNP) hybrid fillers, and CNT-AgNP in the presence of varying loadings of ionic liquid (IL). SEM micrographs confirmed the successful decoration of AgNP on CNT surfaces and the formation of filler networks, facilitated by connecting end-to-end CNT bundles with AgNP. The incorporation of CNTs into NR resulted in superior mechanical strength, initial modulus, torque difference, crosslink density, vulcanization rate, and electrical properties in contrast to the gum NR vulcanizate. The decoration of CNT surfaces with AgNP and their end-to-end connection further elevated these properties. Additionally, the introduction of IL to form NR/CNT-AgNP/IL nanocomposites accelerated the curing properties, evidenced by an increased cure rate index and reduced scorch and cure times. Incorporating 1 to 3 phr of IL significantly enhances mechanical, thermo-mechanical, torque difference, crosslink density, and associated properties. However, exceeding 3 phr leads to property deterioration due to notable formation of filler agglomerations and IL pools in the NR/CNT-AgNP/IL nanocomposites containing 5 and 7 phr of IL. In contrast, electrical conductivity continues to increase beyond the 3 phr IL threshold, attributed to the emergence of IL pools serving as a highly conductive electrolyte. Graphical abstract.