Enhanced energy conversion efficiency in the surface modified BaTiO3 nanoparticles/polyurethane nanocomposites for potential dielectric elastomer generators

The dielectric elastomers have been widely studied in last decades due to their excellent electromechanical conversion ability. Herein, two kinds of polyurethanes (PU) with different molecular weights were used and the results demonstrated that incorporating low molecular weight (MW) PU into high MW PU not only caused the decrease in elastic modulus but also induced a high elongation at break. The optimal performances of PU mixture were observed when the content of low MW PU was 20 wt% and the PU mixture with 20 wt% low MW PU was used as the matrix in this work. In order to achieve a high electromechanical conversion performance, the surface modification of BaTiO3 (BT) nanoparticles by 4,4'-diphenylmethane diisocyanate (MDI) was carried out and the obtained BT products (BT-MDI) were used as fillers for the PU nanocomposites. The permittivity of BT-MDI/PU nanocomposites with 6 wt% fillers increased to 8.6 at 1 kHz and the elongation at break of nanocomposites at this filler loading still remained as high as 1070%. Because of the enhanced properties, the achieved energy-conversion density reached 2.88 mJ/cm(3) at 900 V, and the conversion efficiency was up to 1.56 %. The results reveal that an effective surface modification of nanoparticles is beneficial for the improvement of electromechanical conversion behavior of composite dielectric elastomers due to both the excellent dispersion of BT-MDI nanofillers and the improved compatibility between BT-MDI nanoparticles and PU matrix.