Is metallocene polyethylene blend with HDPE more compatible than with PP?

The thermal, mechanical and viscoelastic properties for two binary blends, metallocene polyethylene (MCPE) - high density polyethylene (HDPE) and MCPE - polypropylene (PP), have been investigated to compare the compatibility and molecular micro-mechanism of blending. We report in this work, the MCPE blends with HDPE and PP are immiscible which is understood by two distinct melting peaks. The modulus, yield stress and tensile strength at break decrease with MCPE, whereas the elongation at break becomes almost unchanged up to about 50% MCPE and then abruptly increases with MCPE. The beta relaxation shifted to higher temperature with MCPE in HDPE-MCPE system. However lower content of MCPE shows discernible two beta relaxation in PP-MCPE blends. These results conclude the degree of compatibility. HDPE-MCPE > PP-MCPE.