Characterizing Shape Memory and Mechanical Properties of Pellet‐Based <scp>3D</scp> ‐Printed <scp>PETG</scp> / <scp>HDPE</scp> Blends for <scp>4D</scp> Printing Applications

ABSTRACT This study aims to develop high‐performance PETG‐HDPE blends for additive manufacturing, with a focus on optimizing their shape memory behavior and thermomechanical properties for industrial applications. Three blends with PETG concentrations of 55 wt.%, 70 wt.%, and 85 wt.% were prepared through melt compounding and characterized using tensile testing, dynamic mechanical thermal analysis (DMTA), shape memory evaluation, and scanning electron microscopy (SEM). Tensile testing revealed an 18.6% enhancement in strength (19.73 to 23.36 MPa) with increasing PETG content, while DMTA showed PETG's dominant role in thermomechanical performance, evidenced by a glass transition at 87°C (Tan δ = 1.52) and a storage modulus reduction from 1095.2 to 24.50 MPa (67.58°C–100.83°C). Shape memory tests demonstrated excellent fixity (91%–95%) and recovery ratios (84%–93%), with the 85 wt.% PETG blend achieving optimal performance. SEM analysis revealed improved interfacial bonding and reduced void formation at higher PETG concentrations, correlating with the enhanced mechanical and shape memory properties. These results highlight the suitability of PETG‐HDPE blends for 4D printing applications, where the 85 wt.% PETG formulation enables programmable, geometry‐specific transformations under thermal stimuli—critical for aerospace actuators and adaptive industrial components.