Structural, morphological, optical and thermoresistive study of the polyaniline/polylactic acid/ZnO films produced by solution blow spraying for temperature sensors

Abstract

The present study aimed to obtain polyaniline/polylactic acid/ZnO (PAni/PLA/ZnO) films via Solution Blow Spraying (SBSp) in order to evaluate their structural, morphological, optical and thermoresistive properties in application such as in temperature sensors. The SBSp technique is a variation of Solution Blow Spinning (SBS), allowing film deposition on any surface using pressurized air and a polymeric solution. ZnO was synthesized via combustion reaction, a method known for producing nanosized particles. PLA was incorporated in the proportion of 10 wt%, while ZnO concentrations ranged from 10% to 60 wt %. Structural analyzes were performed by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) for the polymers; the morphology of the films was analyzed by Scanning Electron Microscopy (SEM); Ultraviolet–visible (UV-VIS) spectroscopy was performed to obtain the bandgap of the material; thermal analysis was carried out by thermogravimetry and the thermosensitive properties were evaluated by a multimeter in a muffle. XRD results confirmed that the PANi/PLA/ZnO film was obtained using the SBSp method, with crystalline phases corresponding to ZnO and PANi. SEM showed an agglomerated and porous appearance of the samples. Decomposition temperatures according to thermogravimetric analysis (TG) were in the range of 200–400 °C, showing that under this regime the films can present their thermoresistive properties without decomposing with temperature. The bandgap was in the range of 2.32–3.92 eV, confirming values of a semiconductor, and that the presence of PLA did not affect this property. Thermoresistive tests demonstrated a Negative Temperature Coefficient (NTC) behavior, indicating that the PAni/PLA/ZnO films obtained by SBSp possess thermoresistive properties suitable for low-temperature sensing applications.