Materials Science and Engineering A 528 (2011) 3003–3006 Contents lists available at ScienceDirect Materials Science and Engineering A journal homepage: www.elsevier.com/locate/msea Rapid communication A novel approach for producing polymer nanocomposites by in-situ dispersion of clay particles via friction stir processing Mohsen Barmouz a , Javad Seyfi b,∗ , Mohammad Kazem Besharati Givi a , Iman Hejazi c , Seyed Mohammad Davachi b a Department of Mechanical Engineering, University College of Engineering, University of Tehran,Tehran,Iran b School of Chemical Engineering, University of Tehran, P.O. Box 11155-4563, Tehran,Iran c Department of Polymer Engineering, Amirkabir University of Technology, Tehran, Iran article info Article history: Received 15 November 2010 Received in revised form 11 December 2010 Accepted 21 December 2010 Available online 30 December 2010 Keywords: Hardness measurement Nanostructured materials Polymer Friction stir processing abstract A novel method based on friction stir processing was developed for fabrication of polymer/clay nanocom- posites to enhance the dispersion state of nanoclay particles and surface mechanical properties. X-ray diffraction, transmission electron microscopy, microhardness and rheological analysis were employed to investigate the effect of processing parameters on morphology and surface mechanical properties. An attempt was made to establish correlations between the significantly enhanced microhardness values and FSP-induced dispersion of nanoclay. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Surface properties of polymeric materials are critically impor- tant in many applications and are strongly influenced by the structure and composition of the outermost molecular layers. Gen- erally, special surface properties regarding hardness, hydrophilicity and crystallinity are needed for successful application of polymers in wide applications such as coatings, friction and wear, compos- ites, etc. [1]. Unfortunately, polymers usually do not possess the required surface properties for these applications. Hence, a great deal of research studies have been focused on surface modification of polymers without changing the bulk properties. There have been some reports on surface modification techniques used on polymer substrates such as active screen plasma nitriding [2]. High density polyethylene (HDPE) is the third largest commod- ity thermoplastic worldwide. Since HDPE is durable, chemically non-reactive, inexpensive and easy to process, it has numerous applications in various industries. But due to the absence of special surface properties, HDPE cannot be considered for special applica- tions. Polymer-clay nanocomposites have been the focus of academic and industrial attention in the two last decades because of their ∗ Tel.: +98 21 88679982; fax: +98 21 88679986. E-mail address: Jseyfi@gmail.com (J. Seyfi). outstandingly improved mechanical, barrier, thermal, and/or other properties relative to the original polymer matrix [3]. Literature shows that microhardness of nanocomposites strongly increases with the clay addition [4,5]. In all these studies, in order to enhance the surface mechanical properties of polymers, nanoclay particles were directly mixed within the bulk polymer either in the melt or solution state. Being able to change a material’s surface properties during its manufacturing process will provide commercial benefits and open up new applications. Friction stir processing is a solid- state technique used for material processing in order to modify microstructural and mechanical properties. During this process, temperature of material does not reach melting point but severe plastic deformation occurs on the processing zone. It is also possible to produce a surface composite layer by this process [6–8]. Based on the above remarks on the need for surface modifica- tion of polymers and the high potential of friction stir processing in improving the microstructural and mechanical properties of the material’s surfaces, FSP could be a promising method to enhance the clay dispersion and thus surface properties of polymers such as hardness. To the best of our knowledge, this is the first time that such a method is being employed for in-situ dispersion of nanopar- ticles in order to improve their dispersion state in polymers with the aim of higher hardness properties. In this study, X-ray diffrac- tion and rheological analysis are also used to probe the dispersion state of nanoclay particles in the system. 0921-5093/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2010.12.083