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Abstract
Clay-based polymer nanocomposites are well known for their many advantageous properties, e.g., electrical, thermal and optical properties, especially the greatly reinforced mechanical properties. No matter how fast improvement of these materials was made during the last decades, there are still some problems needing to be solved to accelerate their development. One is the absence of cost-effective method to effectively control the dispersion of nanofillers in the polymer matrix. Another is the lack of structure-property relationships.
There are three structures exhibited when montmorillonite (MMT) is dispersed inside nylon 6 matrix to generate nylon 6/MMT nanocomposites. One is traditional composites; the other is intercalated and exfoliated nanocomposites, respectively. Among them, exfoliated nanocomposites behave the best of mechanical properties. In this research, we study the structure and mechanical properties of exfoliated nylon 6/MMT nanocomposites. It is widely recognized that interface has a crucial influence on the properties of nanocomposites. Experimentalists have used many advanced instrumentations and techniques to characterise the structure of the nanocomposites and quantitatively determine their interface characteristics. However, the nano-scale nature of the system and the ambiguity between the interface and the matrix, have made quantifying the thickness of the interface extremely challenging. Thus, interface s effects on the overall mechanical performance of the nanocomposites are yet to be clarified. We investigate the interfacial interactions between different components (e.g. MMT, polymer, and surfactant) and interface structure and determine its thickness of both fully and partially exfoliated nanocomposites by molecular dynamics (MD) simulations. Then effective clay clusters (fully exfoliated single-layer effective clay cluster and partially exfoliated two-layer and three-layer effective clay clusters) are built and treated as building blocks in the nanocomposites. Young s moduli of these building blocks are calculated and analysed by MD simulations. Finally, traditional micromechanics methods are applied to calculate the overall Young s moduli of nylon 6/MMT nanocomposites. Our predicted results agree well with the measured results from literature from both qualitative and quantitative points of view. Thus it is demonstrated that effective clay clusters can be used as building blocks to approximate the overall Young s moduli of clay-based polymer nanocomposites. Furthermore, the ensuing research studies compressive moduli of nylon 6/MMT nanocomposites by using the same calculation methods as overall Young s moduli.