Analyzing the influence of particle size and stiffness state of the nanofiller on the mechanical properties of epoxy/clay nanocomposites using a novel shear-stiff nano-mica
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The mechanical properties of epoxy/clay nanocomposites were investigated in relation to the particle size and shear stiffness state of the dispersed nanoplatelets. The fracture toughness and the underlying toughening mechanisms were thoroughly discussed in detail. For this study, a highly pure synthetic fluorohectorite with large lateral extensions (≈3.8 µm) was used and compared to natural montmorillonite characterized by significantly smaller lateral extensions (≈400 nm). Moreover, for the synthetic fluorohectorite, the subtle balance between layer charge density and the hydration enthalpy of interlayer cations allows for switching between a shear-labile and shear-stiff state, something impossible for the natural material. To ensure optimum dispersion, solution blending was followed by three roll milling for nanocomposite preparation. The addition of all three types of clay used in this study provoked a decrease in glass transition temperature, which indicated a moderate interfacial strength. The maximum increase in fracture toughness and strain energy release rate was observed for the nanocomposites prepared with the large and shear-stiff fluorohectorites at a particle content as low as 2.2 vol%. Morphological investigations by scanning electron microscopy of the fracture surfaces revealed the contribution of several micro-mechanical toughening mechanisms. In contrast to the small natural montmorillonite, the large synthetic nanoplatelets promoted additional energy dissipating mechanisms such as crack deflection and crack pinning leading to an enhanced fracture toughness. These observations are discussed in details using fracture mechanical approaches.
KeywordsFracture Toughness Energy Release Rate Neat Epoxy Crack Deflection Static Light Scattering
The authors highly acknowledge the financial support from the German Research Foundation in the frame of the Collaborative Research Center SFB 840: “From particulate nanosystems to mesotechnology,” and from the German Federal Ministry for Economic Affairs and Energy (FKZ 0327895E).
- 20.Goossens D (2008) Techniques to measure grain-size distributions of loamy sediments: a comparative study of ten instruments for wet analysis. Sedimentology 55:65–96Google Scholar
- 21.KA Carrado, A Decarreau, S Petit, F Bergaya, G Lagaly (2006) Synthetic clay minerals and purification of natural clay. In: Handbook of clay science Bergaya F, Theng BKG, Lagaly G (eds), Chapter 4, 1st edn. Elsevier, AmsterdamGoogle Scholar
- 22.Kinloch AJ, Young RJ (1983) Fracture behaviour of polymers. Applied Science Publishers, LondonGoogle Scholar
- 27.Mouloud A, Cherif R, Fellahi S, Grohens Y, Pillin I (2012) Study of morphological and mechanical performance of amine-cured glassy epoxy–clay nanocomposites. J Appl Polym Sci 124:4729–4739Google Scholar