Piezoelectric nanocomposite films based on anionic waterborne polyurethane and barium titanate nanoparticle: Fabrication, microstructure, and property characterization

Abstract We report the fabrication, microstructure, thermal property, and piezoelectric performance of flexible waterborne polyurethane (WPU) nanocomposite films reinforced with barium titanate (BT) nanoparticles with ~50 nm diameter. An anionic segmented WPU was synthesized via bulk polymerization, and its nanocomposite films containing 10–40 wt% BT were fabricated via aqueous dispersion casting and hot pressing. Although the BT nanoparticles interacted with the urethane groups of the WPU hard segment by inducing the separation of the semicrystalline soft segment, they were aggregated in the WPU matrix. Accordingly, the glass transition temperature of the WPU matrix decreased with BT content, but the melting temperature increased. As the BT content increased in the nanocomposite films, the thermal decomposition temperature of the WPU soft segment showed a slight decrease, while the decomposition temperature of the hard segment increased. Additionally, the residue at 600°C increased significantly from 2.0% for neat WPU film to 36.3% for the nanocomposite film containing 40 wt% BT. The piezoelectric outputs attained by the nanocomposite films increased with BT content. Under compressive stress of 23 kPa, the nanocomposite film containing 40 wt% BT was able to achieve the highest piezoelectric voltage of ~0.51 V, a current of ~43.0 nA, and an electric power of ~21.9 nW. For the nanocomposite film, a linear relationship between the piezoelectric out voltage and the applied compressive stress with a slope of ~0.0253 was also observed. Highlights Anionic waterborne polyurethane (WPU) with hard/soft segments is synthesized. Barium titanate (BT) nanoparticles are adopted as a piezoelectric nanofiller. WPU/BT nanocomposites are manufactured by dispersion casting and hot pressing. Specific interactions between BT nanoparticles and WPU hard segments exist. Piezoelectric outputs of nanocomposites increase with BT content and stress.