Eswaraiah et al. Nanoscale Research Letters 2011, 6:137 http://www.nanoscalereslett.com/content/6/1/137 N A N O E X P R E S S Open Access Inorganic nanotubes reinforced polyvinylidene fluoride composites as low-cost electromagnetic interference shielding materials Varrla Eswaraiah1,2, Venkataraman Sankaranarayanan2, Sundara Ramaprabhu1* Abstract Novel polymer nanocomposites comprising of MnO2 nanotubes (MNTs), functionalized multiwalled carbon nanotubes (f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f- MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10-16S/m to 4.5 × 10-5S/m (3.2 × 10-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region. Introduction In recent years, electronics field has diversified in tele- communication systems, cellular phones, high-speed communication systems, military devices, wireless devices, etc. Due to the increase in use of high operating frequency and bandwidth in electronic systems, there are concerns and more chances of deterioration of the radio wave environment known as electromagnetic interference (EMI). This EMI has adverse effects on electronic equipments such as false operation due to unwanted electromagnetic waves and leakage of infor- mation in wireless telecommunications [1]. Hence, in order to maintain the electromagnetic compatibility of the end product, light weight EMI shielding materials are required to sustain the good working environment of the devices. EMI shielding refers to the reflection or absorption or multiple reflection of the electromagnetic radiation by a shielding material which thereby acts as a shield against the penetration of the radiation through it [2]. Conventionally, metals and metallic composites are * Correspondence: ramp@iitm.ac.in 1Alternative Energy and Nanotechnology Laboratory (AENL), Nano Functional Materials, Technology Centre (NFMTC), Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India Full list of author information is available at the end of the article used as EMI shielding materials as they have high shielding efficiency owing to their good electrical con- ductivity. Even though metals are good for EMI shield- ing, they suffer from poor chemical resistance, oxidation, corrosion, high density, and difficulty in pro- cessing [3]. The chemical resistance of polymer is defined largely by its chemical structure. In the present case, polyvinylidene fluoride (PVDF) has been chosen as the base polymer because of its excellent chemical resis- tance [4,5] over a variety of chemicals, acids, and bases. It is well known that the addition of lower amount of inorganic nanotubes (1-10 wt.%) will not affect the basic properties such as chemical resistance, strength, etc. of the base polymer [6,7]. Ever since the discovery by Ijima [8], carbon nanotubes (CNT) have attracted consider- able research interest owing to their unique physical and chemical properties [9,10]. CNT-polymer compo- sites gained popularity recently for various applications [11-13] due to the distinct advantages of polymers and nanofillers (CNT) such as lightweight, resistance to cor- rosion, and chemical resistance of the polymer as well as high electrical conductivity, high aspect ratio, and high mechanical strength of CNT [14,15]. Previous studies on CNT-polymer composites show that carbon nanotubes can be considered as advanced © 2011 Eswaraiah et al; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.