Digitally Tuned Multidirectional All-Polyethylene Composites Via Controlled 1d Nanostructure Formation During Extrusion-Based 3d Printing

Fused filament fabrication (FFF) of polyethylene (PE) reactor blends containing high amounts of nanophase-separated disentangled ultrahigh molar mass polyethylene UHMWPE) generates self-reinforced all-PE composites that exhibit superior mechanical properties. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and small/wide-angle X-ray scattering (SAXS/WAXS) analyses reveal that flow-induced crystallization accounts for the in situ formation of fiberlike extended-chain one-dimensional (1D) nanostructures that nucleate high-density PE (HDPE) crystallization, resulting in "shish-kebab" structures as a reinforcing phase. Both the orientation and the content of the 1D nanostructures are controlled by varying the three-dimensional (3D) printing parameters like nozzle temperature, printing pathway, and printing speed. Compared with conventional HDPE, this self-reinforcement simultaneously improves the stiffness (+100%), tensile strength (+200%), and impact strength (+230%) of the material. For the first time, the limited scope of conventional melt processing is advanced and 3D printing, guided by computer design, is applied to enable the fabrication of both unidirectional and digitally tuned multidirectional all-PE composites with quasi-isotropic properties as a function of the 3D printing pathway.