Mechanical and dynamic mechanical properties of polyolefin blends: effect of blend ratio and copolymer monomer fraction on the compatibilisation efficiency of random copolymers

The mechanical and dynamic mechanical properties of isotactic polypropylene/high density polyethylene (PP/HDPE) blends, as a function of blend ratio and compatibiliser concentration were analysed. Ethylene propylene random copolymers (EPDM) with three different monomer fractions were used as compatibilisers. Compatibilisation improved the mechanical properties (except Young’s modulus) of the blends, considerably. The compatibiliser with 1:1 monomer fraction was found to be most efficient. A detailed discussion on the fundamental reasons responsible for the deterioration of properties in the absence of compatibilisers and the improvement of properties in the presence of compatibilisers was presented. The tensile strength of the uncompatibilised blends was theoretically modelled using Nielsen’s and Nicolais-Narkis models. The Young’s and storage moduli of uncompatibilised blends were compared with those predicted by various theoretical models. Attention was paid to correlate the mechanical properties of both compatibilised and uncompatibilised blends with their phase morphology.