Hierarchical structure manipulation of UHMWPE/HDPE fibers through in-reactor blending with Cr/V bimetallic catalysts

A dramatically improved, uniform distribution of commercial ultrahigh molecular weight polyethylene (UHMWPE) with high-density polyethylene (HDPE) via solution blending, rather than that of melt blending, is often apparent in experimental investigation. Recently, we demonstrated that a UHMWPE/HDPE blend created by in-reactor polymerization with a Cr/V bimetallic catalyst supported on modified silica can obtain an even better molecular chain distribution while saving energy and solution costs, even more so than experiments using a solution blend. Furthermore, by gel-spinning processing, an abundance of hierarchical, interlocking shish-kebab crystals were generated in the in-reactor polymerized blend fibers (IRBFs), exhibiting better mechanical properties than those of solution blend fibers (SBFs). The tensile strength of the IRBFs increased by about 20% under the same draw ratio, since the interlocking shish-kebab structures contributed to homogenous deformation. The two kinds of fibers exhibit high crystallinity and have a highly oriented shish-kebab structure. Compared with the SBFs, the IRBFs inclined to form longer shish features and smaller kebab sizes, and the draw process was more conducive to the transformation of kebab to shish structures. Thus, the IRBFs can obtain an excellent hierarchal network structure, benefiting more from the hot-stretching process. Our work lays a solid foundation for the efficient fabrication of high-performance UHMWPE/HDPE fibers as well as the optimization of an original polyethylene catalyst system.