Excellent triple-shape memory effect and superior recovery stress of ethylene-vinyl acetate copolymer fiber

Shape memory composites are often made from fibers with a shape memory effect. Ethylene-vinyl acetate copolymer (EVA) is a commonly used material in manufacturing shape memory polymer fibers for composites. It is well known that triple-shape memory effect (triple-SME) is important for SM materials to meet multiple temporary shape changes. In this work, the excellent triple-SME of EVA fiber is first reported by regulating EVA fiber crystalline structure transformation through controlling thermo-mechanical coupling conditions. The wide melting transition temperature is observed by dynamic mechanical analysis and differential scanning calorimetry. Thermo-mechanical testing verifies that the EVA fiber has the ability to achieve an excellent triple-SME and tunable reversible SME. Besides, the maximum recovery stress (at iso-strain ε = 5%) is 1.45 MPa when the actuation temperature is 75 °C. The synthesized EVA fiber with an excellent shape memory effect and a superior recovery stress is highly promising for various applications such as deployable space structures and fasteners, artificial muscle and self-finishing smart textiles, etc.