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Nanocomposites comprising nanoscale platelets derived from layered silicates treated with an organic modifier in thermoplastic vulcanizates (TPV) and PP/EPDM blends were prepared by direct melt intercalation. The interlayer spacing and dispersion of the nanoclay are greatly affected by polar forces between the nanoclay and the polymeric matrix material. The mechanical properties strongly depend on the structure and morphology of the nanocomposites, which can be modified by phase partitioning of the reinforcements. Morphology characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM) provides the basis for understanding the observed structure-property relationships in this class of materials. With the increase of organoclay loading, the tensile modulus of TPV/clay nanocomposites increases by up to 170% at 8 wt% organoclay loading, while tensile strength gradually decreases with increase of organoclay loading. In the physical blend systems, the tensile modulus increases for all PP/EPDM blend compositions and generally shows higher values in the case of selectively reinforced phases in blends having a continuous PP matrix. The tensile strength of those blends decreases at higher nanoclay content no matter how blending is performed. However, the tensile strength may increase when sufficient selectively reinforced EPDM phase is present. Polym.

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A comprehensive review of the journal literature dealing with short-fiber reinforcement of various types of elastomers over the past decade indicates an underutilization of the potential for this type of reinforcing agent within the rubber industry. Whereas the properties of continuous cords are not necessarily duplicated by discontinuous fibers, a unique and useful behavior is imparted by this latter class of reinforcement to the rubber matrices containing them. In many cases, new capabilities are generated for elastomeric materials by the nature of the short fiber composite—it is not just a combination of cords and rubber, but effectively a different compound in which individual dispersed filaments can synergistically interact with the rubber, much like a polyblend or alloy. Moreover, the structure, and hence the properties, of this blend can be manipulated through the processing or fabrication operation, as well as by compounding. Thus, new opportunities are opened for growth and expansion of the classical rubber market.

Fracture initiation and fracture propagation toughening (R‐curve behavior) of polyamide 6,6 (PA‐66) polymers with different types of layered silicate clay having nanoscale (fully dispersed) or multiscale (mixed nanoscale/microscale) structure were studied. These results were compared to fracture data for conventional kaolin clay particulate reinforcements and a PA‐66 polyblend containing rubber and rigid poly(styrene‐co‐acrylonitrile) particulates. The stiffness increase due to the intercalated clay was the same as would be predicted by classical models for conventional elongated reinforcements at the same volume fraction level. The special benefit of the nanoscale reinforcement derived from their high surface area of contact with the matrix. Toughness in layered silicate clay composites was enhanced by better dispersion of the clay, by exfoliation of the clay layers, and by a stronger clay/matrix interface. A multiscale microstructure was found to be the more desirable microstructure, combining toughness from the nanodispersed clay with resistance curve behavior from the micrometer‐sized particulates. Fracture toughness was proportional to the crack‐tip plastic zone size at fracture, indicating that the clay reinforcements, by influencing shear deformation in the crack tip region, played an important role in promoting toughness. There was indirect evidence for the formation of a zone of damage within the crack‐tip plastic zone that could explain why toughness was not optimal.