Material characterization of polyurethane dielectric elastomer

Polyurethane (PU) is a promising dielectric elastomer (DE), however increasing its dielectric constant is essential for PU to become a viable DE. Incorporating graphene oxide (GO) as a filler has the potential but may increase dielectric loss and conductivity. Zirconium silicate (ZrSiO4) is an alternative, but excessive use potentially decreasing the actuation strain. This study delves into the impact of polydopamine (PDA) modification on GO and ZrSiO4, and their influence on the dielectric and mechanical properties of PU composites. Nanoparticles were modified with PDA, then mixed with PU matrix at various weight percentage through melt-mixing process. The modified nanoparticles (GOPDA and ZrSiO4-PDA) significantly enhances the dielectric constant of PU composites compared to unmodified nanoparticles. PU with GO-PDA shows reduction in dielectric loss and conductivity with 70% and 50% decrement compared to unmodified GO due to insulative barriers in GO-PDA. However, ZrSiO4 modification results in lattice contraction, leading to an increase in dielectric loss (up to 100%) and conductivity (up to 354%) for composites with ZrSiO4-PDA. A hybrid composite incorporating 2.5 wt.% of GO-PDA and 30 wt.% of ZrSiO4 was synthesized, demonstrating elevated dielectric constant up to 25, albeit with elevated losses (up to 0.48) and conductivity (up to 5 X 10- 7 S/m), which may stem from a reaction between PDA and ZrSiO4, affecting the insulating properties of GO-PDA and causing lattice contraction of ZrSiO4. This study comprehensively explores the effects of PDA modification on GO and ZrSiO4 in PU-based elastomers, shedding light on electrical, mechanical properties, and morphology. It informs potential strategies for developing DE for generators or actuators.