Development of polyurethane-titania nanocomposites as dielectric and piezoelectric material

Flexible polyurethane (PU)-titania nanocomposites of different compositions are prepared by a melt-mixing technique. Two different sequences of mixing method are adapted to prepare two different sets of composites. All these composites show composition-dependent dielectric properties, and composites with tunable dielectric properties can be obtained through judicial adjustment of composition. The morphology of these composites has been investigated by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and scanning probe microscopy (SPM). Dielectric properties at low frequency regions are found to depend on morphology. These composites show excellent piezoelectric behaviour, where the dielectric constant and conductivity of these flexible composites change appreciably with changes in applied stress. The dielectric breakdown strength of these composite is also measured. To understand the thermal stability of these composites, thermogravimetric analysis has been applied and it was found that a composite containing 12.49 vol% titania shows higher thermal stability, beyond which, stability decreases due to the photocatalytic effect of titania.