Transparent PMMA-based nanocomposite using electrospun graphene-incorporated PA-6 nanofibers as the reinforcement Biyun Li, Huihua Yuan, Yanzhong Zhang ⇑ State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, China College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, China article info Article history: Received 1 September 2013 Received in revised form 26 September 2013 Accepted 30 September 2013 Available online 10 October 2013 Keywords: A. Nanocomposites A. Functional composites B. Mechanical properties E. Electro-spinning Graphene abstract This paper deals with development of a novel poly(methyl methacrylate) (PMMA) based transparent nanocomposite made from using electrospun graphene-incorporated-Nylon 6 (Gr/PA-6) nanofibers as the reinforcement, in which both the mechanical and optical properties of the developed Gr/PA-6/PMMA nanocomposite are paid particular attention. By introducing the concept of electrospun PA-6 nanofibers as the dispersing carrier for graphene nanosheets and by employing a facile self-blending co-electrospin- ning approach for homogeneously hybridizing nanocomposite nanofibers of Gr/PA-6 with PMMA fibers, aggregation issue of the involved nanofillers (i.e., the Gr nanosheets and the Gr-incorporated PA-6 nanof- ibers) within the PMMA matrix could be effectively addressed. Visible light transmittance and tensile mechanical properties of the hot-pressed Gr/PA-6/PMMA nanocomposite were examined in relation to the loading fractions of the Gr nanosheets in the nanocomposite. It was demonstrated that a significant enhancement in tensile mechanical properties of the Gr/PA-6/PMMA nanocomposite was accomplished at a Gr loading of merely 0.01 wt%; that is, a nearly 56%, 113% respective improvement of tensile strength, Young’s modulus, and noticeably above 250% increase of fracture toughness were achieved, while the transmittance of the nanocomposite was maintained above 70% (in other words, less than 10% loss in transparency in comparison with neat PMMA) in the visible wavelength range of 400–800 nm. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction It is well known that polymer composites reinforced with tradi- tional micro-sized fibers offer the highest mechanical performance compared with other kinds of reinforcements. However, for trans- parent composites, as the name suggests, there is additional con- cern on transparency. In order to improve the mechanical properties with no sacrifice in transparency, one promising solu- tion is to use nano-scaled reinforcements (e.g., nanofibers or nano- particles) with dimension significantly less than visible light wavelength (400–800 nm) [1–3]. The available large surface area of nano-scaled reinforcements also offers the possibility of realiz- ing efficient transfer of applied load from the matrix to the rein- forcing element. Electrospinning is currently the most powerful technique for fabricating continuous nanofibers with typical diameters in a few hundreds of nanometers. Previous studies have demonstrated the feasibility of using electrospun nanofibrous membranes to prepare transparent nanocomposites with enhanced mechanical properties and minimal loss in transparency [1,3,4]. However, there is still much room for improvement by developing high performance nanofibers as reinforcement, conducting structural design via uti- lizing oriented nanofibers instead of non-wovens [5,6], and most of all having nanofibers homogeneously dispersed and distributed within the polymer matrices. A variety of proposed solutions such as coaxial electrospinning [4], suction filtration [7], and solution casting [8], have evidently demonstrated the necessity and critical role of nanofiber dispersion in achieving high performance trans- parent nanocomposites. Apart from the one-dimensional nanofibers, various inorganic nanoparticles such as clay, silica, metallic oxide and carbon nano- tube, are also considered as favorable nano-reinforcements for improving mechanical, electrical, thermal, optical or other proper- ties of the polymers of interest [6,9,10]. Particularly, graphene with a high optical transparency (97.4% at 550 nm for monolayer Gr film and is usually reduced by approximately 2.2–2.3% for an additional monolayer) [11–13] and Young’s modulus of 1 TPa and an ultimate strength of 130 GPa, is one of the strongest materials ever mea- sured [14]. This makes graphene an outstanding reinforcement for polymers with optical transparency if the formation of aggregates or agglomerates is avoided. Considering the confine- ment effect with the electrospun nanofibers, electrospinning could be one of the most convenient dispersing methods to use [15]. 0266-3538/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.compscitech.2013.09.022 ⇑ Corresponding author. Address: College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, 2999 North Renmin Road, Shanghai 201620, China. Tel./fax: +86 21 6779 2374. E-mail address: yzzhang@dhu.edu.cn (Y. Zhang). Composites Science and Technology 89 (2013) 134–141 Contents lists available at ScienceDirect Composites Science and Technology journal homepage: www.elsevier.com/locate/compscitech