Synergistic effect of carbon nanotubes and clay platelets in reinforcing properties of silicone rubber nanocomposites Bratati Pradhan, 1 Saheli Roy, 1 Suneel Kumar Srivastava, 1 Anubhav Saxena 2 1 Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India 2 Momentive Performance Materials Programs, GE India Technology Centre Pvt. Ltd, EPIP, Phase 2, Hoodi Village, Whitefield Road, Bangalore 560 066, India Correspondence to: S. K. Srivastava (E - mail: sunit@chem.iitkgp.ernet.in) ABSTRACT: Fine powders of montmorillonite (MMT)/multiwalled carbon nanotube (MWCNT) hybrids have been prepared by simple grinding of MWCNT with MMT in different weight ratios of MMT to MWCNT (10 : 1, 6 : 1, 3 : 1, 1 : 1, and 1 : 3) and character- ized by wide-angle X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. These stud- ies have established the formation of the exfoliated structures of MMT/MWCNT (1 : 1) hybrid, in which MWCNTs exist in the state of single nanotubes that are adsorbed and intercalated on the surface and in between the MMT nanoplatelets. The hybrid has subse- quently been used as reinforcing nanofiller in the development of high-performance silicone rubber (SR) nanocomposites, and a remarkably synergistic effect of MMT and MWCNT on SR properties has been observed. The tensile strength of SR containing 1% w/ w of the MMT/MWCNT (1 : 1) hybrid is improved by 215%, whereas the SR filled with MMT or MWCNT alone showed an improvement of 46 and 25%, respectively, over that of unfilled SR. In addition, SR/1 wt % MMT/MWCNT (1 : 1) nanocomposites also exhibit the maximum improvement in thermal stability corresponding to 10% weight loss by 70  C, crystallization and melting temperatures increased by 8 and 6  C as inferred from thermogravimetric analysis and differential scanning calorimetry, respectively. This approach is promising for the preparation of high-performance SR nanocomposites by using different dimension nanofillers together. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41818. KEYWORDS: clay; graphene and fullerenes; nanotubes; properties and characterization; thermal properties Received 27 June 2014; accepted 24 November 2014 DOI: 10.1002/app.41818 INTRODUCTION Silicone rubber (SR) are one of the most important functional polymers, which have received considerable interest owing to their unique properties, e.g., excellent physical, chemical, and thermally stability; low glass transition temperature; clarity; bio- compatibility; nonreactivity; and low surface energy. However, its low surface energy accounts for a lack of intermolecular interaction, providing poor mechanical strength of elastomers. Therefore, SR needs to be reinforced for majority of its applica- tions. 1–3 In recent years, one-dimensional (1D) multiwalled car- bon nanotubes (CNTs) are found to be an important filler in the development of high-performance polymer nanocompo- sites. 4–6 However, CNTs are poorly dispersed in many common organic solvents and polymeric matrix. Although this problem has been overcome by covalent functionalization, 7,8 it introduces the defective sites in the nanotubes, deteriorating the properties of CNTs as reinforcing filler in the formation of polymer nano- composites. 7,8 Therefore, it remains a major challenge to find out simple ways and means to enhance the dispersion of CNTs in the development of polymer/CNT nanocomposites. Montmo- rillonite (MMT) is another two-dimensional (2D) inorganic material consisting of 2 : 1 layer structure with a central alu- mina octahedral sheet sandwiched in-between two silica tetrahe- dral sheets. However, it needs to be organomodified for its better dispersion as well as its compatibility in the fabrication of polymer nanocomposites. 9 In very recent years, the hybridization of 1D nanotubes and 2D lamellar flakes to form MMT/CNT hybrid nanomaterials is more interesting owing to its versatile and tailormade properties than those of the individual materials. 10–14 These hybrids have been prepared by in situ growth of CNTs on clay layers 11–13 and wet mixing of organically modified CNTs and clay. 14 According to Lan and Lin, 10 the aggregation of CNT in various organic mediums (toluene, dimethylformamide, and ethanol) or in Additional Supporting Information may be found in the online version of this article. V C 2014 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2015, DOI: 10.1002/APP.41818 41818 (1 of 11)