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Unformatted text preview: JOM March 2007 50 Overview Nanocomposite Materials Polymer nanocomposites are polymer matrix composites in which the fillers are less than 100 nm in at least one dimen- sion. These composites have exhibited extraordinarily interesting properties. A defining feature of polymer nano- composites is that the small size of the fillers leads to a dramatic increase in interfacial area as compared to tradi- tional composites. This interfacial area creates a significant volume fraction of interfacial polymer with properties dif- ferent from the bulk polymer even at low loadings. The properties and structure of this interfacial region are not yet known quantitatively, presenting a challenge both for controlling and predicting the properties of polymer nanocomposites. This paper provides a brief overview of polymer nanocomposites with emphasis on the impact of the interfacial region. Polymer Nanocomposites: A Small Part of the Story* L.S. Schadler, L.C. Brinson, and W.G. Sawyer 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.1 0.2 Volume Fraction of Filler Volume Fraction of Interfacial Polymer 0.3 0.4 2 nm Particles 2 nm Tubes 0.5 1 10 nm Particles 10 nm Tubes 50 nm Particles 50 nm Tubes INTRODUCTION Polymer nanocomposites can be defined as polymers containing fillers with one dimension smaller than 100 nm (Figure 1a). In contrast to traditional polymer composites with high loadings (60 vol.%) of micrometer-sized filler particles, polymer nanocomposites are being developed with very low loadings (less than 5 vol.%) of well-dispersed nanofillers. While elastomeric compos- ites with nanoscale spherical fillers have been in use for more than 100 years, 1 in the last 15 years new fillers have emerged, providing an opportunity for the develop- ment of high-performance multifunc- tional nanocomposites. For example, transparent conducting polymer/nano- tube composites are under development as solar cell electrodes, 2 nanoparticle- filled amorphous polymers are being used as scratch-resistant, transparent coatings in cell phone and compact-disc technology, 3 and nanoparticles are being considered for enhancing matrix proper- ties of traditional composites to increase out-of-plane properties and add conduc- tivity and sensing capabilities. 4 The recent resurgence of interest in polymer nanocomposites has emerged for several reasons. First, nanoscale fill- ers often have properties that are differ- ent from the bulk properties of the same material. For example, as the size of silicon nanoparticles decreases, the band gap changes, and the color of the par- ticles changes. 5 As another example, single-wall carbon nanotubes can exhibit stiffness, strength, and strain-to-failure that substantially exceeds that of tradi- tional micrometer-diameter carbon fiber....
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- Spring '08
- Composite Materials