Flow-induced crystallization and resulting anisotropic properties

It is well known that flow gradients can have a major influence on the crystallization of semi-crystalline polymers. Not only the nucleation rate can change dramatically, but also the type of nuclei can change depending on the level of orientation of the molecules; especially the orientation the high molecular weight fraction. The level of modeling of flow induced crystallization (FIC) has improved quite a lot the last few years. Even the influence of hard particles on the local stress level and the FIC behavior is now studied numerically. These models reveal the importance of the coupling between rheology and FIC. Having available reliable parameters values that enter these models is becoming more urgent and so is the need for reliable and accessible experiments that combine rheological characterization methods with structure characterization methods. We use shear and extensional flow combined with different structure characterization methods such as microscopy, TEM and SEM, SALS, FIB and WAXS/SAXS on both linear and a branched polymers. The evolution of the detailed structural information, including crystallinity, lamellae thickness, long spacing, spherulite size and orientation, is linked to the evolution of the rheological parameters and providing, in this way, the input for the models. Next, we link this structural information to mechanical properties, in particular the impact strength.A full multi scale approach is used that allows for taking into account anisotropy at different levels and the influence of both soft and hard particles.