Influence of processing conditions on dual-phase continuous blend system of thermoplastic polyurethane with ethylene-propylene-diene monomer elastomer

摘要

In the present work, we extend the investigation on the influence of processing conditions on the morphology, the mechanical properties, and the rheology of the blends of thermoplastic polyurethane (TPU) and ethylene-propylene-diene monomer elastomer (EPDM). Scanning and transmission electron microscopies show that the dual-phase continuous morphology of the blends was strongly dependant on the EPDM composition, processing temperature, and the shear rates. The network structure of the EPDM domain in TPU matrix became finest and most regular for the blends containing 7 wt % EPDM. It was also found that high shear rate favored the formation of the perfect network structure. Furthermore, the blends prepared at 180 degrees C present finer and more perfect network structure than those at the other processing temperatures. The competition of compatible and incompatible segments of TPU with EPDM during melt blending plays an important role in development of the dual-phase continuous morphology. This was reflected through the influence of processing conditions on the rheological properties, and was also verified by the Davies equation's prediction. The tensile properties present a significant improvement with addition of EPDM, and obtained the optimum value for the blends containing 7 wt % EPDM. The influence of different processing parameters on the mechanical properties is associated with their influence on the morphology, and better tensile properties are obtained in the processing conditions, in which, the finer and more perfect network structure of EPDM domain is presented. These facts confirm that the dual-phase continuous morphology is the main advantage for higher tensile strength, elongation at break, and Young's modulus can be well controlled by different processing conditions for the improvement of mechanical properties. (c) 2006 Wiley Periodicals, Inc.