Shape memory polymer/CNT composites and their microwave induced shape memory behaviors

In this paper, the practicability of actuating the shape recovery of thermo-responsive shape memory polymers (SMPs) filled with carbon nanotubes (CNTs) has been investigated. When exposed to microwave radiation, the embedded CNTs were expected to absorb the external electromagnetic energy and act as node heating sources in the SMP/CNT composites. In this way, the SMP could be volumetrically heated and subsequently this would lead to a fast actuation. Although the pure SMP was not responsive to microwave radiation, the microwave absorption ratio in the SMP/CNT composites significantly increased along with the increasing amount of added CNTs or the microwave frequency. The influence of the CNTs on the thermomechanical properties of the SMP composites has been investigated and analyzed using scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) methods. The shape recovery behaviors of the SMP composites with 1 wt%, 3 wt% and 5 wt% CNTs were successfully triggered by microwave radiation. The shape recovery process together with the temperature distribution were recorded with an infrared video camera simultaneously. Furthermore, the selective heating characteristic of the microwaves was also experimentally demonstrated on a SMP composite with a nonuniform CNT concentration. The microwave actuation method is potentially a better choice for the wireless remote shape control of SMP/CNT based functional structures.