Enhancing Printability, Mechanical, and Shape Memory Properties of <scp>4D</scp> Printed Linear‐Low‐Density Polyethylene (<scp>LLDPE</scp>) Through Blending With Polyethylene Terephthalate Glycol (<scp>PETG</scp>)

ABSTRACT Polyethylene (PE) is one of the most widely used commodity plastics, yet its integration into the pioneering field of polymer‐based 3D and 4D printing remains challenging. Conversely, polyethylene terephthalate glycol (PETG) is a widely utilized material in 3D and 4D printing, capable of mitigating the limitations of PE in these applications through blending. Herein, three weight percentages of 15, 30, and 45 wt% PETG were added to low‐density polyethylene (LDPE), and the 3D printed samples were subjected to a comprehensive evaluation of mechanical properties, morphology, thermal analysis, and shape memory properties. The results of dynamic mechanical thermal analysis (DMTA) revealed a noticeable peak in tan δ around 80°C, which becomes more pronounced in blends with higher PETG content. Scanning electron microscopy (SEM) analysis showed that increasing PETG concentration in 3D‐printed LDPE/PETG blends transforms their morphology from distinct, void‐rich phases at 15 wt% PETG to improved dispersion at 30 wt% PETG, and finally to a co‐continuous, strongly adhered structure at 45 wt% PETG, indicating enhanced compatibility. Tensile testing demonstrated a shift from ductile to brittle behavior as the PETG content increased. Shape memory evaluation of blends indicated that higher PETG concentrations improve shape recovery performance, with the 30 wt% PETG blends achieving the highest recovery ratio (88.7%) and the 15 wt% PETG blends showing the lowest recovery ratio (68.7%). These results represent a significant step toward incorporating LDPE into commercial 3D printing materials.