Hybrid <scp>GNP</scp> / <scp>MWCNT</scp> Nanofillers in Shape Memory Thermoplastic Polyurethane: Synergistic Enhancement of Mechanical Properties, Thermal Diffusivity, and Shape Recovery

ABSTRACT Thermally responsive shape memory thermoplastic polyurethanes (SMTPs) are attractive for aerospace, biomedical, and soft robotic applications due to their ability to recover their original shape upon heating. However, their applications are limited by low mechanical strength, poor thermal diffusivity, and slow shape recovery. In this study, SMTP composites reinforced with 1 weight percentage (wt.%) multiwalled carbon nanotubes (MWCNTs), 1 wt.% graphene nanoplatelets (GNPs), and hybrid MWCNT/GNP nanofillers were fabricated by a twin‐screw extrusion followed by injection molding. Thermal, mechanical, and shape memory properties of individual and hybrid reinforcements were investigated by differential scanning calorimetry (DSC), tensile testing, flexural testing, impact testing, thermal diffusivity measurements, and shape‐recovery tests. The balanced hybrid composite containing 0.5 wt.% MWCNTs and 0.5 wt.% GNPs exhibited the highest tensile strength, with an improvement of 34% over neat SMTP. The GNP‐dominated hybrid composite exhibited the highest thermal diffusivity of 0.146 mm 2 /s. The shape recovery time of approximately 34 s was observed, a 43% reduction compared to neat SMTP. SEM observations confirmed improved nanofiller dispersion and formation of a synergistic network in hybrid composites. These results show that hybrid reinforcements are effective in improving the mechanical, thermal, and shape recovery performance of SMTP composites.