Preparation And Study Of All Organic Dielectric Elastomer Material

Dielectric elastomers (DEs) are a kind of electroactive polymers (EAPs) that can transfer electrical energy to mechanical energy. Compare with other EAPs, DEAs have attracted much attention in the last two decades because they have many advantages such as large actuation strain, fast response, light weight, and reliability. DEs find many applications in industry such as artificial muscle, flat-panel speakers, inchworm robots, and biomechanical field. However, the current high applied voltage (>50 kV/mm) limits their applications. Thus, the problem is how to achieve large actuation strain under low electric field. Based on the mechanism of electrical actuation, the ways are improving the dielectric constant of the material and decreasing the elastic modulus of the materials (maitain mechanical strength).This thesis reports methods in preparing DEs with high dielectric constant and low elastic modulus. In this paper a novel organic conductive filler with high dielectric constant and low elastic modulus was prepared by mixing gelatin and glycerol (GG). Then GG was added into electrospun thermoplastic polyurethane (TPU) nonwoven to make GG/TPU composites. The densely packed TPU nonwoven fabric not only ensures the good mechanical strength of GG/TPU DE, but also separates GG filler and stops the formation of the GG continuous phase, preventing the formation of a conducting path under an exerted electric field. The novel GG filler considerably increases the dielectric constant and decreases the elastic modulus of the GG/TPU DE. As a result, the as-prepared DE exhibits good mechanical strength and 5.2% actuation strain at a very low electric field (0.5 kV mm-1).Meanwhile, this thesis also reports the fabrication and study of carbon nanospheres(CNS)/TPU dielectric elastomers.The FTIR spectroscopy results showed that CNS with many hydroxyl groups can form hydrogen bonds with TPU molecules, leading to a good dispersion of CNS in the TPU matrix and an improved tensile strength of CNS/TPU composites. More interestingly, by influence the hydrogen bonding between TPU moleculars, CNS disrupted the crystallization of TPU, resulting in the decrease in elastic modulus and hysteresis loss of the composites.The dielectric constant at 103 Hz increased from 7.1 for pure TPU to 137.3 for the composite with 5 wt% of CNS. The great increase in dielectric constant and the decrease in elastic modulus result in the largely improved actuation strain at low electric field of CNS/TPU composites. This thesis reports two simple ways in preparing DEs with large actuation strain under low electric field, increasing the possibility of industry fabrication and the application of DEs.