Preparation and mechanical performance of rubber-modified thermoplastic polymer-clay nanocomposites

Thermoplastic polymer nanocomposites reinforced with layered silicates have attracted considerable interest recently due to large enhancements in tensile stiffness and strength can be achieved at very small loading levels of fillers. Such enhancements in mechanical properties are attributed to homogeneous dispersion of clay platelets with high aspect ratios in polymer matrix and the exfoliation of clay particles to a certain degree. However, the incorporation of clays into polymers often deteriorates their tensile ductility and impact toughness. This is because the clay platelets are ineffective to induce crazing and shear yielding in polymer matrix as in the case of spherical rigid nanoparticles. To restore the toughness, it is necessary to add at least 5-20 wt% rubber particles into the polymer-clay nanocomposites. Moreover, super-tough thermoplastic-clay nanocomposites based on polypropylene and polyamide can be produced by adding rubber content > 25 wt%. The tensile, impact and fracture behavior of rubber toughened nanocomposites are related to the clay and elastomer contents as well as the processing conditions.