Melt rheology, morphology, and mechanical properties of thermoplastic/rubber blends

This work reports on the melt rheology, morphology, mechanical properties, and accelerated UV aging resistance of binary blends of polypropylene (PP) and high-density polyethylene (HDPE) thermoplastics with two kinds of rubber: ethylene-propylene-diene terpolymer (EPDM) and polyisoprene rubber (IR). The blends were also formulated with calcium carbonate (CaCO3) filler, and the rubber was partially crosslinked with dicumyl peroxide (DCP). The blends were compared with a commercial thermoplastic rubber (TPR). The effect of the thermoplastic/rubber ratio, and the addition of CaCO3 and DCP on the melt rheology, morphology, and mechanical properties was investigated, looking for a TPR with good mechanical performance, ease of processing, and aging resistance. An increase in mechanical properties and melt viscosity with the rubber and peroxide content on the blend was observed. On the other hand, the CaCO3 incorporation reduces the elongation and increases the melt viscosity of the blend. The morphology of the blends examined by scanning electron microscopy (SEM) revealed that the adding the filer improved the dispersion of EPDM onto the PE and PP.