M.V. Murugendrappa

Synthesis, characterization and D. C. conductivity studies of polypyrrole/molybdenum trioxide composites

In-situ polymerization of pyrrole (PPy) was carried out with molybdenum trioxide (MoO3) in the presence of oxidizing agent ammonium persulphate to synthesize polypyrrole/molybdenum trioxide composites (PPy/MoO3) by chemical oxidation method. The PPy/MoO3 composites were synthesized with various compositions viz., 10, 20, 30, 40 and 50 wt % of MoO3 in pyrrole. The powder X-ray diffraction (XRD) spectrograph, suggests that they exhibit semi-crystalline behavior. The Fourier Transform Infra-Red Spectroscopy (FTIR) reveals the stretching frequencies are shifted towards higher frequency side. The surface morphologies of these composites using Scanning Electron Microscopy (SEM), show that MoO3 particles are embedded in PPy chain to form multiple phases. The D.C. conductivities were studied in the temperature range from 30–200°C.The values of the conductivity increase up to 40 wt % MoO3 in PPy and decreases thereafter. This percent weight is the percolation threshold for these composites. The composites obey percolation theory. The dimensions of molybdenum trioxide particles in the matrix have a greater influence on the conductivity values.

Lab Scale Study on Humidity Sensing and D.C. Conductivity of Polypyrrole/Strontium Arsenate (Sr 3 (AsO 4 ) 2 ) Ceramic Composites

In-situ polymerization of pyrrole was carried out with strontium arsenate (ceramics) in the existence of oxidizing agent ammonium persulphate to synthesize polypyrrole/strontium arsenate composites by chemical oxidation method. The polypyrrole/strontium arsenate composites were synthesized with various compositions viz., 10 to 50 wt % of strontium arsenate was placed in polypyrrole. The surface morphologies of these composites were analyzed using Scanning Electron Microscopy (SEM) which confirmed the embedment of strontium arsenate particles in PPy chain. The Fourier Transform Infra-Red spectra (FTIR) revealed the shift of lengthens frequencies towards elevated frequency area. The powder X-ray diffraction patterns (XRD) disclosed the crystalline behavior exhibition of the composites. Thermographs of thermal analysis (TG/DTA) exposed the stronger stability of polypyrrole/strontium arsenate composites than PPy. D.C. conductivity reveals that, the strontium arsenate concentration in polypyrrole is accountable for the variant of conductivity of the composites. The results of the study signify the increment of D.C. conductivity for 40 wt % of strontium arsenate in polypyrrole. The temperature reliant conductivity dimension shows the thermally activated exponential behavior of PPy/Sr3(AsO4)2 composites. The reduction in electrical resistance was experienced, when the polymer composites were bare to the wide range of relative humidity (Rh) (from 30 to 95%). This reduce is due to enhance in surface electrical conductivity ensuing from humidity fascination and also due to capillary abridgment of water causing change in conductivity within the sensing materials. The composite shows sensitivity in the range 30 to 95% Rh, we also studied response and recovery time.

Characterization and Evaluation of Activation Energy for Dc Conductivity of Polypyrrole/Nickel Zinc Iron Oxide Nanocomposites

Polymer nanocomposites of Polypyrrole and Nickel zinc iron oxide (NiZnFe2O4) are prepared by insitu polymerisation using Ammonium persulphate as oxidising agent. Various nanocomposites have been prepared by varying the level of additive material NiZnFe2O4. The formation of nanocomposites and changes in the structural and microstructural properties were investigated by using XRD, FTIR, and SEM analysis. The size of the particle was analysed by XRD using Scherrer equation and found to be in the range of 15nm 20nm. The lattice parameters were evaluated by W-H plots. DC conductivity has been measured in which activation energy (Ea) of the composites has been evaluated. Activation energies were evaluated from Arrhenius plots for all compositions. Results show that the incorporation of additive material increases the activation energy ‘Ea’ for the DC conductivity of the composites, compared to the base polymer. The increase in the activation energy ‘Ea’ is found to depend on the level of the additive in the composites. Significant increase (196%) in DC conductivity was observed for nanocomposite of 50 wt.%. Therefore such polymer nanocomposites find applications in microwave absorbers, sensors, electromagnetishielding etc.,

Ac Conductivity and Dielectric Studies of Polypyrrole Copper Zinc Iron Oxide Nanocomposites

Polypyrrole and polypyrrole/copper zinc iron oxide (CuZnFe2O4) nanocomposites are synthesized by in-situ polymerisation in different weight percentages using oxidation method. Dielectric and conductivity behaviours of Polymer nanocomposites of various composition were investigated using impedance spectroscopy at different temperatures and frequencies (100 Hz-5 MHz). The dielectric properties of host polymer matrix have been improved by the addition of nanoparticles and are found to be highly temperature dependent. Both Dielectric constant and Dielectric loss decreased with increase in frequency for all composites, indicating a normal behaviour of dielectrics. Increase in dielectric constant and dielectric loss was observed with respect to temperature, which is attributed to increase in number of dipoles due to thermal energy. Dielectric relaxation is observed at low frequency range, relaxation time is calculated from the dielectric loss peaks. The highest conductivity was observed at 373K for all nanocomposites. The significant increase in dielectric constant makes them a potential candidate for dielectrics in capacitors used for decoupling, timing, filtering, and many other functions.