Dynamically Vulcanized Nanocomposite Thermoplastic Elastomers Based on EPDM/PP (Rheology & Morphology)

Abstract

This study examines the rheological and morphological properties of dynamically vulcanized nanocomposite thermoplastic elastomers (TPV nanocomposites) based on PP/EPDM. Rubber contents of 20, 40, and 60% were used with polypropylene of different viscosities at 2 wt.% of nanoclay. We performed rheological and morphological characterizations on the nanocomposites using X-ray diffraction, transmission electron microscopy, scanning electron microscopy and rheometry in small amplitude oscillatory shear. The effects of polypropylene viscosity, maleic anhydride grafted polypropylene (PPMA), and composition were also investigated. The storage modulus (G) of the TPV nanocomposites (without PPMA) containing 20, 40, and 60% rubber significantly increased in comparison with similar but unfilled samples and also a further increase in the G from the incorporation of the PPMA in the samples. The agglomeration of the clay considerably decreased when the rubber content was increased in the TPV nanocomposites. The yield stress of the prepared TPV nanocomposite, based on a low-viscosity PP, increased more than that of the sample from high viscosity PP. The TPV nanocomposites containing 20, 40 and 60% EPDM exhibited a strong elastic modulus that tended to level off (plateau) at low shear rates. These results were attributed to strong interfacial interactions between the nanoclay and TPV matrix and, also, the existence of the physical three-dimensional network structure formed between the cured rubber particles, as evidenced by the morphological features of the samples. A Carreau-Yasuda law with yield stress and a linear viscoelastic model, taking into account the maximum packing volume () were used to describe the melt linear viscoelastic properties of the TPV nanocomposites.