Tuning Crystalline Morphology of High-Density Polyethylene by Tailoring its Molecular Weight Distribution for Coupling with a Secondary Flow Field

Designing a material from the chain architecture to achieve a tailored crystalline morphology in a molding condition is a grand challenge. Here, the crystalline morphology of high‐density polyethylene is tuned by tailoring its molecular weight distribution for coupling with the secondary flow field under gas‐assisted injection molding (GAIM). The selected N‐PE and the tailored B‐PE have similar weight‐average molecular weights (Mw), but the latter possesses a broader molecular weight distribution (MWD). Although a weaker flow field is triggered due to the slightly slower melt advance rate in the cavity, B‐PE is capable of better coupling with secondary flow field in comparison with N‐PE, which causes much more oriented crystals in molded parts, such as shish kebab, and shows higher orientation behaviors in the corresponding zones. These significant results provide an important step to explore the coupling of chain architectures and secondary flow field for designing desired crystalline morphology. Both macroscopic flow and molecular rheology need to be overall considered for morphological control under the injection molding with a secondary fluid injection. In this work, the coupling of HDPE chains to a secondary flow field has been applied to design much more shish‐kebab structures.