Multifunctional NR/MWCNTs nanocomposites constructed via combining volume exclusion of SiO2 microspheres with interface reinforcement of tannic acid

Due to the intricate entanglement and strong π-π stacking interaction, carbon nanotubes are hard to be dispersed uniformly in polymer matrix, thereof it is difficult to produce high-performance and multifunctional polymer/multiwalled carbon nanotubes (MWCNTs) nanocomposites with low filler contents by traditional polymer processing technologies. Herein, the interspersed SiO2 microspheres (m-SiO2)/MWCNTs hybrid fillers (ISMH), which are not only dispersed easily in rubber matrix via mechanical blending but also have a biomimetic interface with the rubber matrix via natural tannic acid (TA), have been developed successfully. Benefiting from the volume exclusion of m-SiO2, a small amount of MWCNTs can form a dense three-dimensional (3D) network in natural rubber (NR) matrix, endowing NR/ISMH nanocomposites with high functionalities. When MWCNTs loading is 0.33 phr, the electrical conductivity of NR/ISMH nanocomposite can reach the equilibrium value ~10-4 S·cm−1. When MWCNTs loading is 1.67 phr, the thermal conductivity and compression temperature rise of NR/ISMH nanocomposite is ~0.32 W·m−1·K−1 and 9.3 °C, respectively, corresponding to an improvement of +22% and −28% relative to the neat NR matrix. Additionally, thanks to the biomimetic interface constructed by covalent and non-covalent bonds via TA, the NR/ISMH nanocomposites also have exhibited excellent mechanical properties. When the ISMH-30 loading (mass ratio of m-SiO2 : MWCNTs = 30: 1) is 20 phr, the comprehensive mechanical properties of NR/ISMH nanocomposite reach the best. The tensile strength, tear strength, elongation at break and DIN wear volume are 28.7 MPa, 43.7 MPa, 625% and 0.18 cm3, corresponding to an improvement of +58%, +16%, +11% and −31% relative to the neat NR matrix, respectively. In a word, the as-fabricated NR/ISMH nanocomposites have the advantages of low cost, high performance and versatile functions, endowing them with great potential applications in antistatic rubber products, vibration-isolated rubber products, and green tires, etc.