A polymer network based on thermoplastic polyurethane and ethylene-propylene-diene elastomer via melt blending: morphology, mechanical properties, and rheology

Blends of thermoplastic polyurethane (TPU) and ethylene-propylene-diene elastomer (EPDM) were prepared via a melt blending, and morphology, mechanical properties, and rheology were studied. Scanning electron microscopy (SEM) micrographs demonstrated that a network of EPDM domain was formed in TPU matrix, and became finer and more perfect with addition of 8 wt% EPDM into TPU. Dynamic mechanical analysis (DMA) and Fourier transformed infrared spectroscopy (FTIR) investigation indicated that EPDM was thermodynamically miscible with the soft segments of TPU and incompatible with the hard segments. The formation of the network was resulted from the competition of compatible and incompatible segments of TPU with EPDM. The tensile strength and elongation at break achieved a significant improvement with addition of EPDM, and obtained the optimum values of 39.21 MPa and 2659%, respectively, when EPDM content was 8 wt%. PEO-g-MA as a compatibilizer was employed to improve the compatibilization between EPDM and the hard segments of EPDM, and consequently, the network became finer and more perfect. The evaluation of rheological properties revealed that the introduction of EPDM into TPU resulted in a reduction of the viscosity at high shear rate and a decrease of the flow activation energy; thus the processability of the blends was improved. (C) 2004 Elsevier Ltd. All rights reserved.