Morphology Development Of Dynamically Vulcanized Thermoplastic Elastomers Based on PP/EPDM in a Co-rotating Twin Screw Extruder
Saeed Shafiei Sararoudi, Hossein Nazockdast, A. Asghar Katbab
Dept of Polymer Eng. Amir Kabir University of Technology
IRAN

Keywords: Thermoplastic Elastomer , Dynamic Vulcanization, Twin Screw Extruder

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Attempts were made to study effect of screw speed, extent of curing and temperature gradient along the twin screw extruder on the morphology development of TPVs based on PP/EPDM (40/60) in a modular corotating twin screw extruder. The morphological studies were carried out on the cryogenically fractured surface of the samples using Scanning Electron Microscopy (SEM) technic. The melt flow behavior and viscoelastic properties of the samples were also investigated by using Rheometric Mechanical Spectrometer (RMS). The extruder total torque as well as the temperature of the zone corresponding to dynamic vulcanized process were found to be increased with increasing the added curing agents up to some extent about which they remained unchanged. A matrix-dispersed type morphology consisting of cured rubber particles dispersed in the polypropylene (pp) matrix was observed for all the TPVs samples. However for a given amount of curing agent the rubber particle size was found to be decreased with increasing the screw speed. The rubber particles size was also decreased slightly with increasing the added curing agent. For the TPVs samples the results obtained from RMS showed a remarkable up-turn in the dynamic viscosity and the storage modulus at low shear rate range, which were found to be increased with increase in added curing agent but decreased with increasing the screw speed. These results were interpreted in terms of network structure resulting from agglomerates formed between the cured rubber particles at low shear rates.