Shape Memory Behavior and Self-Healing Effects of Dynamically Vulcanized TPU/ENR Thermoplastic Elastomeric Blends

In this work, an innovative TPE material architecture with excellent shape memory and self-healing properties has been fabricated by introducing an in situ polymerized zinc dimethacrylate (PZDMA) onto the macromolecular chains of thermoplastic polyurethane (TPU) and epoxidized natural rubber (ENR) via dynamic vulcanization. Damage to the developed material surface could be healed by physical contact between the cut surfaces through a contraction force (i.e., shape memory effect), reassociation of ionic networks, and molecular diffusion of ENR chains at the interface. Interestingly, PZDMA not only promotes the shape memory-assisted self-healing functionality by enhancing ionic interactions with the blend components but also improves mechanical properties by the formation of ionic clusters which act as a reinforcement. The formation of such ionic reversible networks and clusters was evident from temperature dependent Fourier transform infrared spectroscopy, X-ray diffraction, Small angle X-ray scattering, X-ray photon spectroscopy, and transmission electron microscopy studies. The resulting material exhibited excellent shape-fixation ratio (Rf ∼ 95%), shape-recovery ratio (Rr ∼ 98%), healing efficiency (∼80% based on tensile strength of pristine sample and healed sample) and oil swelling resistance (5–6% in ASTM oil #3) at a suitable transition temperature of 80 °C. This work provides a promising route for the fabrication of next generation TPE materials, which may also be developed into innovative programmable elastomeric materials.