Shape-memory polymers (SMPs) are smart materials with the ability to recover from one or several temporary shape deformations into a permanent configuration upon exposure to external stimuli. This phenomenon is referred to as shape-memory effect (SME). Triggers include temperature, electricity, magnetism, irradiation or solvents. Development of SMPs has been driven by potential applications in fields such as construction, aerospace, soft robotics or biomedical devices. Within SMPs, thermo-responsive systems are the most extensively studied. Blending of polymers not only allows for the synergistic combination of favorable material properties, but also enables the cost-effective fabrication of systems exhibiting temperature triggered shape-memory.<br/><br/>In this study we present the characterization of thermo-responsive shape-memory elastomer-thermoplastic-blends. These consist of ethylene-propylene-diene-monomer rubber (EPDM) mixed with different thermoplastic polymers. Herein, the covalently cross-linked elastomer constitutes the permanent phase, whilst the (semi)crystalline thermoplastic component forms switching segments. Emphasis lies on blends with ultra-low-density polyethylene (ULDPE) and propylene-ethylene copolymer (PP-c-PE), which show particularly promising towards multi-shape-memory applications.<br/><br/>Mechanical properties of all materials were determined by tensile testing. Thermal transitions were studied by means of differential scanning calorimetry (DSC), confirming the presence of immiscible polymer blends. Dynamic-mechanical thermal analysis (DMTA) was utilized to investigate thermo-mechanical features and to study dual- and multi-shape-memory effects. Results indicate temperature-dependency and tunability of shape-memory behavior by the choice of raw materials and blending ratios. Moreover, atomic force microscopy (AFM) was utilized to examine blend morphology.

Thermo-responsive shape-memory behavior of elastomer-thermoplastic-blends

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