Synthesis, characterization of elastomer-based ternary composites and investigation of their gas sensor properties

In this study; Polypyrrole (PPy) was synthesized by chemical polymerization method using iron(III) chloride (FeCl3) as oxidant and anhydrous chloroform (CHCl3) as solvent. Triple composites which is composed of poly (cis-1,4 isoprene) (PI) and polystyrene (PS) (PS/PI/PPy) were prepared by using different concentration of PPy. PPy and ternary composites were pelletized for use in gas sensor measurements. The conductivity of the samples was measurement using four-prop technique. The results showed that the conductivity of the samples increase with increasing the temperature. First, the conductivity properties of the pellets in the temperature range of 20-50˚C were measured and then the gas sensor properties against 10 different chemical vapors (solvent) were examined. The measurements of the gas sensor properties of the composites were carried out in a system with temperature control and isolated against material flow. Gas sensor properties of the different composites and PPy were examined against 10 different chemical substance vapors. The best gas sensor property for the composites in terms of effect-response time was obtained in HCl vapor. Since the liquid chemical vapors penetrate the polymer by natural diffusion during the experiments, both the diffusion coefficients for each of the solvents were calculated. Moreover, the time-dependent mass flux balances of these solvents and also the concentration of the solvents in the system were calculated during the measurement period. The porosity and twist factor, which are important criteria in mass transfer, were examined for both PPy and composites by mercury porosimetry. The chemical characterization of the composites was investigated by FTIR. The morphology of the composites was examined by Scanning Electron Microscope (SEM). Moreover, the thermal properties of both PPy and composites were investigated by Thermogravimetric Analysis (TGA). In addition, conductivity of the samples was measured at different temperatures using the four-point technique. Further, X-Ray Diffraction (XRD) analysis results showed that PPy and composites were amorphous. As a result, in this study, novel ternary composites were synthesized by a facile and reliable method. The results showed that these composites have a promising potential for using in gas sensor applications.