Contents lists available at ScienceDirect Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop Multifunctional multi-walled carbon nanotube reinforced natural rubber nanocomposites Thomasukutty Jose a , Grace Moni a , Salini S. a , Ann Jess Raju a , Jinu Jacob George b , Soney C. George a, ⁎ a Centre for Nano Science and Technology, Amal Jyothi College of Engineering, Koovappally P.O., Kottayam 686518, India b Rubber Research Institute of India, Kottayam, Kerala, India ARTICLE INFO Keywords: Natural rubber Multiwalled carbon nanotubes Transport characteristics Mechanical properties Thermal properties Conductivity ABSTRACT The versatility of natural rubber (NR) as an elastomer is of considerable importance in the current scenario. In order to improve the characteristic properties of the elastomer, reinforcing it with nanofillers that possess multifunctional attributes are of great importance. In the present study, multiwalled carbon nanotube (MWCNT) reinforced natural rubber nanocomposites were prepared by two-roll mixing as a function of filler loading. The dispersion of nanotubes in the matrix was confirmed by Transmission Electron Microscopy and Raman analysis. Thermal, mechanical, dynamic mechanical, and transport properties of the nanocomposites were extensively studied. Nanocomposite with 3.5 phr of filler content showed 55% improvement in tensile strength. The thermal stability of the nanocomposites was evaluated with the aid of TGA and DSC analysis. Conductive properties of the nanocomposites were also studied. As the filler loading reaches the value of 3.5 phr, a percolation transition is observed which is accompanied by an increase in dielectric permittivity value of about 1.6 units. The solvent permeability of the composites was considerably reduced due to its reinforcement with nanotubes, following a mechanism that is very close to Fickian. 1. Introduction Elastomers are of great industrial importance due to their high and reversible deformability. In order to enhance their mechanical, thermal, conductive as well as optical properties, it has been incorporated with the nano, micro or macro counter parts. For the past few decades, nanocomposites have attracted a great deal of attention due to their exceptional enhancement in characteristic properties with the intro- duction of low loading of reinforcing content. The elastic material that is obtained from the latex sap of trees of the Genera Hevea and Ficus, namely natural rubber, as such, is not suitable for industrial purposes because of its poor resistance to chemicals and oil substances, instability towards long time exposure to heat, light, etc. Various means were developed to improve the properties of natural rubber by its modification, especially by vulcanization and its reinfor- cement by the introduction of filler component. The reinforcing effects of various fillers such as cellulose, carbon black, clay, graphene, CNT etc to enhance the properties of natural rubber composites were done by several researchers (Abraham et al., 2013; Yaragalla et al., 2015; Abdelmouleh et al., 2007; Alejandro et al., 2007; Frogley et al., 2003; Kueseng and Jacob, 2006; Kin et al., 2006; Razi et al., 2006). Nowa- days, the use of multiwalled carbon nanotubes (MWCNT) as reinforcing agent in elastomeric composites attracts a great deal of attention due to its outstanding properties (Alejandro et al., 2007; Frogley et al., 2003; Kueseng and Jacob, 2006; Kin et al., 2006; Razi et al., 2006). The properties like tensile strength, stiffness and electrical conductivity of the elastomeric composites had increased significantly by the incor- poration of MWCNTs (Inpil et al., 2011; Zdenko et al., 2010; Arash and Nasser, 2011), that are strongly dependent on the aspect ratio, shape and concentration of the filler (Lucia et al., 2012; Martone et al., 2011; Gavrilov et al., 2013; Ayatollahi et al., 2011). Enormous studies were carried out on the application of CNTs in epoxides, thermoplastics, fibers, and elastomers (Frogley et al., 2003; Kin et al., 2006; Razi et al., 2006; Bokobza, 2007; Bokobza and Belin, 2007; Lopez-Manchado et al., 2004). Considerable improvement in physical properties was reported when MWCNTs were incorporated in natural rubber. Kong and co- workers (Zheng et al., 2010) prepared natural rubber/MWCNT nano- composites using latex compounding techniques. They reported that the well dispersed MWCNTs generated a remarkable increase in the tensile strength of the NR with very low filler loading. In another work, improvement in tensile and dynamic-mechanical properties was re- http://dx.doi.org/10.1016/j.indcrop.2017.04.047 Received 9 June 2016; Received in revised form 15 March 2017; Accepted 27 April 2017 ⁎ Corresponding author. E-mail address: soneygeo@gmail.com (S.C. George). Industrial Crops & Products 105 (2017) 63–73 0926-6690/ © 2017 Elsevier B.V. All rights reserved. MARK