Author's personal copy Producing superior composites by winding carbon nanotubes onto a mandrel under a poly(vinyl alcohol) spray Wei Liu a,b , Xiaohua Zhang c , Geng Xu c , Philip D. Bradford b , Xin Wang b , Haibo Zhao b , Yingying Zhang d , Quanxi Jia d , Fuh-Gwo Yuan b , Qingwen Li c, * , Yiping Qiu a , Yuntian Zhu b, * a College of Textiles, Donghua University, Shanghai 201620, China b North Carolina State University, Raleigh, NC 27695, USA c Suzhou Institute of Nano-Tech and Nano-Bionics, Suzhou 215123, China d Los Alamos National Laboratory, Los Alamos, NM 87545, USA ARTICLE INFO Article history: Received 17 March 2011 Accepted 24 June 2011 Available online 30 June 2011 ABSTRACT A simple method for processing high-performance carbon nanotube (CNT)/poly(vinyl alco- hol) (PVA) composites by coupling the spraying of a PVA solution with the continuous wind- ing of CNT sheets from an array onto a rotating mandrel is reported. This method allows the CNT composites to have a high CNT volume fraction, while having a high degree of alignment, long CNTs, and good integration with the matrix, which are extremely difficult to realize simultaneously by other processes. As a result, the composites have a toughness, strength and electrical conductivity up to 100 J/g, 1.8 GPa and 780 S/cm, respectively. Such a one-step synthesis process is promising for industrial productions and also works for dif- ferent types of polymers. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Carbon nanotubes (CNTs) are an order of magnitude stronger than current engineering fibers [1,2] making them ideal rein- forcement for advanced composites. After decades of exten- sive research it still remains a great challenge to synthesize high-performance CNT composites in a manner conducive to large-scale production [3–6]. In order to fully utilize the un- ique properties of CNTs, it is desired to uniformly distribute among the matrix the unidirectionally-aligned long tubes at a high fraction. However, it is difficult to realize such a struc- ture with the existing processing approaches, including the dispersion of CNTs in the polymer matrix and the infiltration of polymers into the interspace of the continuous CNT net- work [5]. The dispersion approach is widely used in the industrial productions of composite films and fibers/yarns, including the solution processing, melt processing, electrospinning, and coagulation spinning [5,7]. However the dispersion of long CNTs is hindered by their entanglement and aggregation, and the CNTs are often limited to a low fraction (<10 wt.%) and randomly orientated. Consequently, the reported strengths of the composites processed by this approach are usually under 400 MPa [8,9]. Further in situ polymerization or hot stretching has not been very effective in improving the mechanical properties [10,11]. It is intrinsi- cally impossible for the dispersion approach to produce the CNT composites with desired structure of long CNTs, high volume fraction, and good alignment. In the infiltration approach, the composites are synthe- sized by infiltrating polymers into CNT preforms, which are produced by using CNT fibers/yarns, sheets, arrays, or bucky papers [5,12]. It is easy to use long CNTs and to improve their alignment to some extent. However, the uniformity of 0008-6223/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2011.06.089 * Corresponding authors: Fax: +86 512 62872552 (Q. Li), +1 919 5153419 (Y. Zhu). E-mail addresses: qwli2007@sinano.ac.cn (Q. Li), ytzhu@ncsu.edu (Y. Zhu). CARBON 49 (2011) 4786 – 4791 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/carbon