Investigation of structural, mechanical, and electrical properties of carbon nanotube reinforced rubber nanocomposites

Abstract

Natural rubber (NR) is an interesting biopolymer. But the modulus and durability of a neat rubber is very low and therefore, addition of reinforcing agents is essential to improve different properties of NR for its specific application. Recently, Carbon nanotubes (CNTs) have also been reported as reinforcing filler in different polymers, because of its unique mechanical, thermal and electrical properties. In this study multiwalled CNTs is used as filler components to reinforce the NR. To realize uniform dispersion of CNTs in the NR matrices MWCNTs are functionalized using HNO3:H2SO4 acid refluxing. Owing to this treatment oxygen containing groups were introduced in the MWCNTs which help the dispersed as well as interact more with the NR matrix. The CNT-NR composites were prepared by simple solution casting method introducing 0.5, 1.0, 1.5 wt% of MWCNTs in NR. For this NR and f-MWCNTs were dispersed in toluene individually and then mixed together and casted in glass tray. From scanning electron microscope (SEM) images it is observed that all the CNTs are well embedded inside the rubber matrix, and no individual CNTs were visible under SEM. It may be due to the uniform dispersion of CNTs which were wrapped by the molecules of NR. EDX spectra confirmed 100% presence of carbon in the composites signifying less or no impurity in it. From XRD a broad peak is observed for NR and CNT-NR composites and therefore indicating that CNT-NR composites are amorphous in nature. FTIR spectra of the MWCNTs confirm the attachment of functional groups (-OH, -COOH) on the surface of the CNTs during acid refluxing of the CNTs. The FTIR spectrum of NR and CNT-NR composites remain similar confirming uniform dispersion of CNTs in the NR matrices. Tensile strength was observed to increase with increasing wt% of CNTs in NR matrices. TG-DTA data shows thermal stability of the composites improved slightly, and degradation of NR delayed with the concentration of CNTs in NR. From DC electrical measurement the current density is observed to increase with increasing wt% of CNTs in the NR matrices at room temperature, also observed to increase with the temperature. Therefore, resistivity decreases with increasing wt% of CNTs in the NR matrices. The activation energy of the experimental composites is observed to vary from 0.17 to 0.26 eV, and observed to decrease with increasing wt% of CNTs in the NR matrices, though slight increase trend shown in the lower voltage region (<20V). The fabricated NR nanocomposites will find interesting applications in different engineering products like robotic arms, tubes, tyres, high charge storage capacitors, electronic packaging, seal pad, electromagnetic interference shielding, etc.