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

Abstract

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 lm) 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.

Transparent Pullulan/Mica Nanocomposite Coatings with Outstanding Oxygen Barrier Properties

“…As for the tensile strength (TS), a significant improvement was recorded only at a concentration of 0.2 wt %, whereas at higher mica loadings TS decreased again, thus approaching the original values of bare PET and pullulan-coated PET. This behavior is most likely related to stress concentration points at the sharp tactoid edges, resulting in flaws (i.e., mechanical failures) at the polymer/filler interface, as already observed in poly(methyl methacrylate) (PMMA)/clay [ 27 ], poly(ethylene terephthalate)/mica [ 4 ], and epoxy/clay [ 7 ] nanocomposites.…”

“…For this reason, the use of synthetic NBBs as attractive nanomaterials is rising at both the academic and industrial level. Until now, only a few studies have dealt with the use of mica in nanocomposites, including thermoset and thermoplastic polymers to improve barrier performance [ 3 , 4 ] and mechanical properties [ 2 , 5 , 6 , 7 ]. There is, however, a gap in the literature that this work aims to fill, specifically dealing with advances regarding mica-based biopolymer nanocomposite coatings.…”

Synthesis of reusable macroporous St/BMA copolymer resin and its absorbency to organic solvent and oil

“…The water/oil mass ratio plays an important role in the formation of particles and their characteristics . When the water/oil mass ratio was too low, the cooling and heat transfer capacity of copolymerization system decreased, and the dispersed phase droplets were easy to collide and aggregate, resulting in the formation of larger polymer particles.…”

Influence of Particle Size on Toughening Mechanisms of Layered Silicates in CFRP

“…It has been shown in the past that many different factors influence the toughening of neat resin. The most important ones are the size of particles, the aspect ratio, the compatibility of the filler and the matrix, the dispersion quality and the orientation of particles [14,15]. In earlier work we have shown that a high particle diameter and aspect ratio are beneficial for a number of toughening mechanisms [11,16].…”