Miscible/partially‐miscible blends of polypropylene—the mechanisms responsible for the decrease of yield stress

Abstract

ABSTRACTIn miscible or partially‐miscible blends of semicrystalline polymer/non‐cocrystallizing low molecular weight component, a decrease of the value of yield stress in comparison to reference (pure) polymer is usually observed. On the example of model polypropylene/nonadecane systems, the mechanisms responsible for the decrease of the yield stress have been identified. It has been proved that during the deformation of polypropylene/nonadecane blends containing low amount of nonadecane (up to 5 wt %) the reduction of the yield stress is caused only by the swelling of interlamellar regions. In the case of the systems containing a moderate amount of nonadecane (7–10 wt %), the reduction of the yield stress is caused by the swelling of interlamellar regions and the reduction of the sample cross‐section effectively participating in transferring of tensile stress. In blends containing nonadecane in the amount of 15–30 wt % the reduction of the yield stress is caused by the swelling of interlamellar regions and strong asymmetrization of nonadecane microdomains, resulting in localizing the deformation along interspherulitic regions and a drastic reduction of the content of polypropylene matrix, effectively participating in transferring of tensile stress between adjacent spherulites. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1203–1214