Gelatineclay nanocomposites of improved properties * YuanQiao Rao * Kodak Research Labs, CTO Organization, Eastman Kodak Company, Rochester, NY 14650-2109, United States Received 30 April 2007; received in revised form 27 June 2007; accepted 28 June 2007 Available online 6 July 2007 Abstract Transparent gelatineclay nanocomposite films were made through solution processing. These films exhibit enhanced physical performance. The Young’s modulus of the composite film was 8.3 GPa, almost three times that of gelatin alone, by dispersing only 10 wt% of one type of montmorillonite clay into the nanosized phase in the gelatin. With the addition of the clay nanoparticles, the crystallinity of gelatin decreases and the melting point increases slightly. X-ray diffraction (XRD) and transmission electron microscopy (TEM) disclosed that the clay nanopla- telets are well exfoliated and dispersed, and are parallel to the plane of film in the nanocomposite film. The property enhancements of gelatin are affected by the dispersion of particles (i.e., intercalation and exfoliation), particle properties (i.e., particle aspect ratio), and particleematrix interaction, as studied by XRD and TEM. The property enhancement can be well modeled using the HalpineTsai equation. Ó 2007 Elsevier Ltd. All rights reserved. Keyword: Clay nanocomposites; Gelatin; Property 1. Introduction At the present time, nanocomposites are receiving a great deal of attention from materials scientists. A composite is called a nanocomposite when the dimension of at least one of its phases is less than 100 nm. It is believed that when the domain size is comparable to the size of a molecule, the atomic and molecular interactions can have a significant influ- ence on the macroscopic properties of that material. Thus, superior property enhancements can be achieved. One subcategory of nanocomposites is the clay nanocom- posite, where nanosized clay particles are used as reinforcing media. Clay is inexpensive, chemically and thermally stable, and has good mechanical properties. Pioneer work at Toyota stimulated the research on polymereclay nanocomposites [1e3]. The platelet-like geometry of clay makes it ideal as a property-enhancing additive. Since then, a variety of poly- mers have been evaluated with the addition of clay, including thermoplastics of nylon 6 [1e4], PET [5e9], nylon-MXD6 [10], polystyrene [11,12], PMMA [13], polypropylene [14], PBT [15], PC/PET blend [16], polyaniline [17], thermosets of epoxy [18], water-soluble polymers such as poly(ethylene oxide) [19e21], poly(vinylpyrrolidone) [22], polyvinyl alco- hol [23], and water born polymeric latex [24]. An enhance- ment in the mechanical properties, an increase in the heat distortion temperature, a lowering in the gas permeability, the use as absorbents, additives for rheological controlling and antistatic material, and an improvement of flame-retardant property [25] were observed in various polymereclay nano- composites. However, property enhancement depends very much upon the system that is chosen. Many nanocomposite systems do not yield the same degree of property enhancement as that achieved by the polyamide clay nanocomposites [1e4]. It is assumed generally that the two factors, the opening up or intercalation, of the clay sheets, and the dispersion of the inter- calated platelets, determine the change in properties. Small and wide-angle X-ray diffractions (XRD) were utilized to in- vestigate the preferred orientation of polymer in the presence of the clay. Attenuated total reflectance Fourier transform in- frared (ATR FTIR) was used to study the interaction between the clay and the polymer. A multiscale micromechanical * Partially presented at 2006 Antec meeting. * Tel.: þ1 585 588 2609; fax: þ1 585 477 7781. E-mail address: yuanqiao.rao@kodak.com 0032-3861/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2007.06.068 Polymer 48 (2007) 5369e5375 www.elsevier.com/locate/polymer