3D Printing of Shape-Memory Polymer based on Polylactic-Acid and Thermoplastic-Elastomer: Investigating of Shape-Memory and Thermo-Viscoelastic Properties

Smart polymers as a subset of smart materials have the ability to memorize their original form and return after reforming by inducing some stimulus. In this study, shape-memory polymers were manufactured in layers by 3D printing methods. Using this method, by controlling the percentage of each material in the sample and layer design the shape memory properties are investigated. The advantages of this method compared to other methods such as blending are the control simplicity of the impacting factors on the shape memory property, construction of complex parts, and improved shape memory property. TPU with elastic property and semi-crystalline PLA materials were used to achieve shape memory property and the samples printed out in TPU-UP and PLA -UP states to investigate the layer design effect. The results of shape memory tests showed that the number of layers, their arrangement, and shape memory properties can be easily controlled and designed. The results of DMTA test indicated that the recovery temperature in layered samples is lower than the other methods and the percentage of PLA and TPU can be controlled the recovery temperature. The recovery speed of layered samples in this study is very higher than previous studies, due to the amount of saved energy in TPU and the multilayered construction. Shape memory tests depicted that TPU increases the recovery ratio and the PLA increases the fixity ratio. The reason lay in the increase of the switching point percentage including crystallization, Tg, and reduction of cross-links which play the role of network cross.