Morphology and mechanical and viscoelastic properties of rubbery epoxy/organoclay montmorillonite nanocomposites

The morphology and mechanical and viscoelastic properties of rubbery epoxy/organoclay montmorillonite (MMT) nanocomposites were investigated with wide‐angle X‐ray scattering (WAXS), transmission electron microscopy (TEM), tensile testing, and dynamic mechanical thermal analysis. An ultrasonicator was used to apply external shearing forces to disperse the silicate clay layers in the epoxy matrix. The first step of the nanocomposite preparation consisted of swelling MMT in a curing agent, that is, an aliphatic diamine based on a polyoxypropylene backbone with a low viscosity for better diffusion into the intragalleries. Then, the epoxy prepolymer was added to the mixture. Better dispersion and intercalation of the nanoclay in the matrix were expected. The organic modification of MMT with octadecylammonium ions led to an increase in the initial d‐spacing (the [d₀₀₁] peak) from 14.4 to 28.5 Å, as determined by WAXS; this indicated the occurrence of an intercalation. The addition of 5 phr MMTC18 (MMT after the modification) to the epoxy matrix resulted in a finer dispersion, as evidenced by the disappearance of the diffraction peak in the WAXS pattern and TEM images. The mechanical and viscoelastic properties were improved for both MMT and MMTC18 nanocomposites, but they were more pronounced for the modified ones. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 103: 3547–3552, 2007     

The effect of dispersion state on PMMA-epoxy-clay ternary blends: In situ study and final morphologies

Two PMMA-epoxy-clay ternary composites have been produced combining the polymerization induced phase separation phenomenon with two individual dispersion processing methods: a melt-blending and an ultrasonic-blending. Transmission electron microscopy (TEM) analysis shows that phase separation between PMMA and epoxy network was obtained in the form of spherical nodules in both processing methods. Organoclay particles were finely dispersed into thermosetting network and predominantly delaminated in ultrasonic-blending, whereas organoclays formed micrometer-sized aggregates in melt-blending. Wide-angle-X-ray (WAXS) studies reveal that exfoliation in the clay particles in three-phase composite was reached. Exfoliation state has been investigated using small angle X-ray scattering (SAXS) in cured systems and during curing reaction. For reacted systems, an exfoliation of platelets can occur through the de-aggregation of large agglomerates into smaller particles composed of a few platelets. For in situ SAXS studies, the distribution of the thicknesses of diffusing entities and the evolution of this distribution with reaction time were followed. This technique has shown also that movements at scale of nanometers of clay tactoids are possible even after the gel point.