Epoxy Nanocomposites with Highly Exfoliated Clay:  Mechanical Properties and Fracture Mechanisms

Abstract

Epoxy/clay nanocomposites with a better exfoliated morphology have been successfully prepared using a so-called “slurry-compounding” process. The microstructures of the nanocomposites (epoxy/S-clays) were characterized by means of optical microscopy and transmission electron microscopy (TEM). It was found that clay was highly exfoliated and uniformly dispersed in the resulting nanocomposite. Characterizations of mechanical and fracture behaviors revealed that Young's modulus increases monotonically with increasing the clay concentration while the fracture toughness shows a maximum at 2.5 wt % of clay. No R-curve behavior was observed in these nanocomposites. The microdeformation and fracture mechanisms were investigated by studying the microstructure of arrested crack tips and the damage zone using TEM and scanning electron microscopy (SEM). The initiation and development of microcracks are the dominant microdeformation and fracture mechanisms in the epoxy/S-clay nanocomposites. Most of the microcracks initiate between clay layers. The formation of a large number of microcracks and the increase in the fracture surface area due to crack deflection are the major toughening mechanisms.

A review on the role of interface in mechanical, thermal, and electrical properties of polymer composites

“…The role of nanofillers in development of tough polymeric products have been reported [155,156]. However, the enhancement of the strength of composites are accompanied with sacrificing toughness of the products [157].…”

Modeling and Simulation of Graphene Based Polymer Nanocomposites: Advances in the Last Decade

“…The energetics of the non-bonding interactions between all pairs of atoms can be defined using Lennard Jones potential (LJ-potential) as given in Equation (6) …”

The application of thermal analysis to the study of epoxy–clay nanocomposites

“…This part of the fabrication procedure is important in respect of the quality of the dispersion of the clay in the epoxy resin, which can depend on a number of factors, including the clay type, the clay loading and the mixing method. The last of these factors may involve, for example, simple mechanical mixing or the so-called slurry method [12][13][14][15][16][17], in which the clay is first dispersed in a solvent, often acetone, before the resin is added and mixed mechanically, and then finally eliminating the solvent. As an illustration of the different degrees of dispersion that can be achieved by these two methods, we compare a mixture of 5 wt% of organically modified (octadecylammonium) montmorillonite (MMT), Nanomer I.30E (Nanocor Inc.), in diglycidyl ether of bisphenol-A (DGEBA) epoxy resin, Epon 828 (Shell Chemicals), which has an epoxide equivalent weight in the range 185 to 192 g equiv -1 , a density of 1.16 g cm -3 , and a viscosity in the range 11,000 to 15,000 mPa.s at 25 °C.…”