Influence of phase morphology and crystalline structure on the toughness of rubber-toughened isotatic polypropylene blends

In the work, ethylene–octene copolymer (POE) toughened isotatic polypropylene (PP) blends with different phase morphologies and crystalline structures were successfully fabricated and their influence on the toughness of PP blends was discussed. POE domains not only played the role of stress concentration to induce stress field around them, but also acted as stress deliverer to transmit stress to the deep into the PP matrix. Elongated domains transmitted stress better, but spherical ones induced a larger stress field. As for the crystalline structure of PP matrix, compared with the “bundle-like” β-crystals, well-developed β-spherulites could induce a larger stress field. The toughness of the blends with different combinations of phase morphology and crystalline structure was also discussed. Only the blend with elongated POE domains and well-developed β-spherulites could achieve super-high toughness. To achieve this goal requires simultaneous optimization of nucleating agent content, POE content and composition, and processing conditions. This work provides a good example to better understand the influence of phase morphology of rubbers and crystalline structure of matrix in rubber-toughed polymer system.