Correlation between the Rheological Behaviours and Morphologies of PP/EPDM Blends in Various Dynamic Vulcanization Systems

Dynamic vulcanization is a well known technique which improves the mechanical properties such as compression set, tensile properties, fatigue, and chemical resistance of thermoplastic elastomers. In this study, three different curing systems (sulphur, peroxide, and phenolic resin) were applied on the polypropylene (PP) /ethylene propylene diene monomer (EPDM) blends. The weight ratio of the blends was PP/EPDM: 40/60. The samples were prepared in an internal mixer at rotor speed of 60 rpm and 190ºC. Dynamic rheological parameters such as storage modulus (G'') loss modulus (G"), complex viscosity (η*), real and imaginary viscosities (η'' and η") damping factor (tan δ), and linearity region were determined at 190°C. The nonlinearity region of dynamic vulcanizated samples was shorter than that of the thermoplastic elastomer without applying dynamic vulcanization. The Cole-Cole, Han, and van Gurp-Palmen plots for all samples were drawn to make correlation between rheologies and morphologies of the blends. It was found that the rheological behaviour of dynamically cured samples was different from uncured sample, because dynamic vulcanization could affect the morphology of the blends. All samples showed morphology of the EPDM rubber dispersed in the PP matrix (droplet-matrix) with different particle size.