Maleic anhydride-modified polypropylene was compounded with commercially available surface-modified montmorillonite in a twin-screw extruder. Recompounding ensured the removal of visible tactoids from the extrudate but TEM and XRD techniques showed nonuniform dispersion of clay platelets. In this study, we investigated the mechanical and fracture properties of nanoclayfilled polypropylene. Emphasis was placed on the fracture characterization of the clay-filled polypropylene. Tensile strength and stiffness increased steadily with an increase in the clay loading. The toughness of compounded materials was characterized using rigorous fracture mechanics. J-integral fracture resistance decreased with an increase in the clay content. The resistance against stable crack growth was compared using the slopes derived from the J-R curve and the tearing modulus concept. A significant amount of crack growth resistance was evident in the nanoclay-filled polypropylene as opposed to other brittle nanocomposites such as the nylon-clay systems.

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A hybrid composite consisting of rubber toughened nylon 6,6, short glass fibers and thermotropic LCP was investigated by varying the content of LCP. It was found that a hybrid composite offered better processability over the glass fiber reinforced polymers alone. The total torque in melt mixing increased with short glass fiber addition but decreased with an increase in LCP content. The thermal stability of the glass fiber reinforced composite was improved by blending with LCP. However, a minimum of 15 wt% LCP was required to realize reinforcement effect from the hybrid composite. The fracture morphology was examined using SEM techniques. Some LCP fibrils could be observed on the tensile fracture surface.

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