ECCM15 - 15 TH EUROPEAN CONFERENCE ON COMPOSITE MATERIALS, Venice, Italy, 24-28 June 2012 1 UNDERSTANDING THE PROPERTY ENHANCEMENT MECHANISM IN EXFOLIATED GRAPHITE NANOPLATELETS REINFORCED POLYMER NANOCOMPOSITES M. Karevan 1 , K. Kalaitzidou 2* 1,2 Georgia institute of Technology, G. W. Woodruff School of Mechanical Engineering, Atlanta, Georgia 30332 * kyriaki.kalaitzidou@me.gatech.edu Keywords: polymer nanocomposite, interfacial interactions, exfoliated graphite nanoplatelets Abstract The focus of this study is to understand how exfoliated graphite nanoplatelets (xGnP) alter the elastic response of the polymers and reveal the mechanisms responsible for the property enhancement observed in xGnP reinforced polymer nanocomposites. The nanocomposites were made by coating and melt compounding followed by injection molding. Polyamide12 (PA12) was used as the matrix. The mechanical properties, including tensile strength and modulus, flexural strength, and thermo-mechanical properties such as the glass transition temperature (T g ) were determined as a function of the xGnP content. The results indicated that a fraction of the polymer chains can be extensively immobilized due to the confinement effect of the xGnP at its large surface area. This suggested presence of a secondary mechanism that is responsible for the PNCs’ enhancement of the mechanical and thermomechanical properties. As shown, based on the rheological and morphological studies, the contribution of such a mechanism is highly affected by the level of xGnP agglomeration. 1 Introduction The large specific surface area and small size of the nanofillers are responsible for the dominant physical/chemical interfacial interactions observed in polymer nanocomposites (PNCs). Such interactions result in i) nanofiller agglomeration due strong van der Waal forces and ii) a region with an extensive degree of immobilized chains along the nanofiller–polymer interface. The aforementioned interfacial phenomena contribute to the interfacial load transfer and hence the reinforcing efficiency of the nanofiller [1-4]. Fabrication of PNCs with predetermined properties is of great importance and is currently done in a non-systematic approach based on trail-and-error testing [5-7]. Therefore, studies have been conducted to modify and employ analytical or computational approaches to design PNCs with engineered properties for targeted applications. However, the majority of the models does not