Electrical Conductivity of Vapor-Grown Carbon Nanofiber/Polyester Textile-Based Composites Niloufar Sabetzadeh, Saeed Shaikhzadeh Najar, S. Hajir Bahrami Department of Engineering, Amirkabir University of Technology, Tehran, Iran Correspondence to: S. S. Najar (E - mail: saeed@aut.ac.ir) ABSTRACT: The main objective of this study was to investigate the capability of vapor-grown carbon nanofibers (VGCNFs) to improve the electrical conductivity of textile-based composites. A combination of mechanical stirring and ultrasonication was used to disperse VGCNFs at various weight fractions (2, 4, 6, 8, and 10 wt %). Textile-based composites were fabricated with a hand-layup method with the application of three fabric types, including carbon, Kevlar, and polyester fabrics. The electrical conductivity of the samples was measured with a four-point probe method, and morphological analysis was performed with field emission scanning electron microscopy. The electrical conductivity of the composite samples was investigated from the standpoint of the VGCNFs’ weight frac- tion, fabric type, cure process temperature. and sonication time. We found that with increasing VGCNF weight fraction, the conduc- tivity increased. Also, the optimum conductivity was obtained at a sonication time of about 2 h. A higher conductivity was observed in the carbon fabric-based composites than in the Kevlar- and polyester-fabric-based composites. Nevertheless, there was no signifi- cant difference among the electrical conductivities of the VGCNF/polyester-textile-based composites prepared at room temperature and 60  C. VC 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 000: 000–000, 2013 KEYWORDS: fibers; nanostructured polymers; polyesters; resins; synthesis and processing Received 4 December 2012; accepted 17 April 2013; Published online DOI: 10.1002/app.39447 INTRODUCTION In recent years, conductive vapor-grown carbon nanofiber (VGCNF)/polymer nanocomposites have been widely considered among scientists because of their exceptional multifunctional properties compared to conventional conductive polymer com- posites. 1,2 Thus, the use of VGCNFs could lead to significant improvements in the electrical, mechanical, and thermal proper- ties of composites. VGCNFs are produced by a vapor-deposition process. Their morphology is similar to that of multiwalled carbon nanotubes (CNTs), where hollow-core nanofibers contain a single or dou- ble layer of graphite planes stacked parallel or at a certain angle to the fiber axis. This kind of nanofiber can be prepared with diameters from 15 to 200 nm and with lengths of a few tens of micrometers; this results in high aspect ratios. 3–5 VGCNFs are distinguished by an extraordinarily high tensile modulus, tensile strength, and electrical and thermal conductivity. Because of their high electrical conductivity, they are suitable fillers for the development of new conductive composites with many applica- tions in the nanoelectronics field transistors, autoelectron emit- ters, diodes, supercapacitors, sensors, electromagnetic shielding materials, and electrostatically paintable materials. 6–10 In partic- ular, most studies have concentrated on epoxy and others polymers, such as polypropylene, nylon, and vinyl ester sys- tems, 11–14 and less attention has been focused on the electrical conductivity of VGCNF/polyester textile nanocomposites. Unsaturated polyester resins (UPRs) are one of the most impor- tant thermoset resins and are used extensively in the composite industry because of their good mechanical properties, ease of processing, low density, and low cost. 15,16 They are useful for applications such as water pipes, chemical containers, buildings construction, electrical appliances, and automotive. 17,18 The use of VGCNFs, CNTs, and carbon black as conductive nanofillers could promote the electrical conductivity of UPR composites. Although most studies have been concerned with CNT/UPR composites, few studies have been reported on the electrical properties of nanocomposite-based UPR and VGCNFs. Torre et al. 19 employed a calendering process to disperse carbon nano- fibers in a UPR. Their investigation on the electrical conductiv- ity of the nanocomposites at different CNF concentrations revealed that the electrical percolation threshold was obtained around 0.3 wt %, where the electrical conductivity switched from 10 213 to 10 27 S/cm. Natsuki et al. 20 described the temper- ature dependence of electrical resistivity for CNF/UPR nano- composites prepared by a solvent evaporation method. They found that the CNF/UPR nanocomposites exhibited quite a low VC 2013 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM WILEYONLINELIBRARY.COM/APP J. APPL. POLYM. SCI. 2013, DOI: 10.1002/APP.39447 1