Rheological behaviour of PP/EPDM blend: The effect of compatibilization

Abstract

Due to different polarity and structure between the thermoplastic and elastomeric phases, most thermoplastic elastomers are incompatible. Poor interfacial adhesion and high interfacial tension between rubber and thermoplastic phases are main reasons for incompatibility of these systems. The blends of polypropylene (PP)/ethylene propylene diene monomer (EPDM) containing 20% EPDM may be compatibilized with maleic anhydride grafted PP (PP-g-MAH) and maleic anhydride grafted EPDM (EPDM-g-MAH) ranging from 0 to 6 phr. The dynamic Theological behaviour of the blends in presence of compatibilizer and applying dynamic vulcanization were studied using parallel plate rheometric mechanical spectrometer (RMS) at 190°C. The Cole-Cole and van Gurp-Palmen plots for all samples were plotted to make correlation between rheology and the obtained morphology of the blends. It was found that the complex viscosity (η*) of the dynamic vulcanized blends levelled up with increase of compatibilizer concentration while for un-vulcanized blends it was levelled off for the same ratio of PP/EPDM. Storage modulus of compatibilized samples showed two relaxations shoulder at high concentration of compatibilizer which at low frequencies is attributed to interfacial relaxation and at high frequencies is related to EPDM droplets. There was no considerable difference among intersection frequencies (ωc) for un-vulcanized samples which means compatibilizer is more effective in combination with dynamic vulcanization. Morphological study showed that the size of dispersed phase decreased with combination of dynamic vulcanization and compatibilization.