Temperature Scanning Stress‐Relaxation Behavior of Dynamically Vulcanized <scp>TPU</scp> / <scp>ENR</scp> / <scp> Fe ₃ O ₄ </scp> ‐Based Thermoplastic Elastomeric Blends

ABSTRACT In this study, the temperature scanning stress‐relaxation (TSSR) behavior of dynamically vulcanized TPU/ENR blends reinforced with Fe 3 O 4 and zinc dimethacrylate (ZDMA) was investigated to understand their network structures and non‐isothermal relaxation dynamics. Two distinct relaxation transitions were observed: a low‐temperature transition (~60°C) attributed to amorphous segment softening and a high‐temperature transition (~120°C) associated with the softening of hard segment, highlighting the complex relaxation mechanisms of these multi‐phase elastomeric system. The microstructural evolution of the blends was investigated using AFM and TEM, revealing improved phase dispersion in the dynamically vulcanized blends. The relaxation dynamics were quantified using the Maxwell–Wiechert model, and their fitting identified three distinct relaxation modes of the developed materials: fast relaxation ( τ 1 ) associated with local segmental motions, intermediate relaxation ( τ 2 ) corresponding to cooperative chain movements, and slow relaxation ( τ 3 ) due to long‐range chain rearrangements and interfacial processes. Furthermore, the influence of network structures of the developed materials was studied using the time–temperature superposition (TTS) principle, which characterized three viscoelastic regimes: glassy, Rouse‐like, and reptation‐like relaxation domains. The dynamically vulcanized blends exhibited slight deviations from the Rouse behavior, indicating restricted segmental mobility attributed to the presence of hard segments and the formation of ionic clusters. In the reptation regime, a high equilibrium plateau modulus, E eq (6.0 MPa), compared to the ENR‐ZDMA sample (0.24 MPa), suggests enhanced crosslink density and phase interactions between ENR and TPU, which effectively restrict chain mobility and enhance the overall mechanical integrity of the thermoplastic vulcanizates.