Effect of polypropylene molecular weight distribution on the balance between the toughness and rigidity of the impact polypropylene composites

Abstract In this study, homo‐polypropylene (HPP) with the same number average molecular weight ( ) while different molecular weight distribution (MWD) are directly melt blended with a polyolefin elastomer (POE) in order to study the effects of the MWD of HPP on the brittle‐ductile transition (BDT) and the balance between toughness and rigidity of the PP/POE composites. The results show that for the same number average molecular weight HPP, the wider the MWD, the higher the brittle strength σ b of the HPP is, and the larger the critical interparticle distance ( ID c ) of the composite is. Larger ID c means lower modifier content can induce the BDT, and thereby leads to less modulus loss of the composites. Namely, the toughened HPP with wider MWD can have a better balance between toughness and rigidity.