Characterization of polyurethane shape memory polymer processed by material extrusion additive manufacturing

Material extrusion additive manufacturing (MEAM), also known as three-dimensional (3D) printing, is a popular additive manufacturing technique suitable for producing 3D shapes using thermoplastic materials. The majority of companies that design and test 3D printing machines work with thermoplastic acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) filaments. It is, however, crucial to utilize different types of filaments for a broader range of applications with different mechanical property requirements. Shape memory polymers (SMPs) are smart materials that react to an applied stimulus in order to recover large strains. MEAM techniques may be used for the production of SMP-based parts, allowing for smart structures to be created in a wide variety of geometries. In this work, a commercial 3D-printer was used to produce 3D printed polyurethane-based SMP specimens. An annealing heat treatment was applied to some of the specimens. Mechanical and thermomechanical testing was conducted to study the effects of testing temperatures and annealing heat treatments on the tensile and shape memory properties of the samples. 3D printing was shown to be a suitable technique for producing SMP parts capable of retaining good shape memory characteristics. Different annealing heat treatments and test temperatures were found to have considerable effects on the SMP specimen properties. In particular, annealing the specimens at 85 °C for 2 h helped to improve the rate of shape recovery and the consistency of mechanical test results.