Thermal and mechanical properties of a polypropylene nanocomposite

An experimental polypropylene (PP) nanocomposite, containing approximately 4 wt % of an organophilic montmorillonite clay, was prepared and characterized, and its properties were compared with those of talc‐filled (20–40 wt %) compositions. Weight reduction, with maintained or even improved flexural and tensile moduli, especially at temperatures up to 70°C, was a major driving force behind this work. By a comparison with the analytical data from a nylon 6 (PA‐6) nanocomposite, it was found that the PP nanocomposite contained well‐dispersed, intercalated clay particles; however, X‐ray diffraction, transmission electron microscopy, dynamic mechanical analysis, and permeability measurements confirmed that exfoliation of the clay in PP was largely absent. The increased glass‐transition temperature (T_g) of a PA‐6 nanocomposite, which possessed fully exfoliated particles, indicated the molecular character of the matrix–particle interaction, whereas the PP nanocomposite exhibited simple matrix–filler interactions with no increase in T_g. The PP nanocomposite exhibited a weight reduction of approximately 12% in comparison with the 20% talc‐filled PP, while maintaining comparable stiffness. Undoubtedly, considerable advantages may be available if a fully exfoliated PP nanocomposite is fabricated; however, with the materials available, a combination of talc, or alternative reinforcements, and nanocomposite filler particles may provide optimum performance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1639–1647, 2003