Maleic acid grafted low density polyethylene for thermally sprayable anticorrosive coatings

Low density polyethylene (LDPE) coatings are being used in an ever growing range of applications. However, non-polar characteristics of LDPE make its adhesion poor to metal substrate and so become less suitable for anticorrosive coating application. An anticorrosive coating can therefore be developed if LDPE is modified with requisite polar groups. In the present work, a polar group has been introduced in polyethylene matrix by grafting maleic acid. Grafted LDPE was characterized by chemical method, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), melt flow index (MFI), particle size analysis and hot stage optical microscopy. The presence of carbonyl peak of high intensity, high acid value and low melt flow index value confirmed grafting of maleic acid on LDPE. Change in crystallization behaviour of LDPE has been noticed after grafting. Grafted LDPE was applied on grit blasted mild steel surface by flame spray technique and adhesion study showed improved adhesion of grafted LDPE than LDPE. The coated panels were evaluated for resistance to corrosion in salt spray, humidity cabinet and seawater. The corrosion resistance of modified LDPE was also studied by AC Impedance technique. Grafted LDPE showed satisfactory corrosion resistance. Grafted LDPE was pigmented with red iron oxide and pigmented composition has shown improved resistance to corrosion in laboratory tests.© Elsevie

Effect of regioregularity on specific capacitance of poly(3-hexylthiophene)

In this communication, we investigate the effect regioregularity of poly(3-hexylthiophene) (P3HT) on the specific capacitance. P3HTs with regioregularities 96, 70 and 58% have been synthesized by Grignard metathesis (GRIM) and FeCl3 methods. The regioregularity of P3HT5 are characterized by nuclear magnetic resonance (NMR), UV-Vis spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. Electrochemical characterizations of the P3HTs reveal significant increase in the specific capacitance with increase in regioregularity. Electrochemical impedance spectroscopy analysis indicates that the charging process is facilitated by increase in regioregularity in P3HT. Stability of P3HTs during repeated charge-discharge cycles, also found to increase with increase in regioregularity. (C) 2012 Elsevier Ltd. All rights reserved

Asymmetric supercapacitor containing poly(3-methyl thiophene)-multiwalled carbon nanotubes nanocomposites and activated carbon

Poly(3-methyl thiophene) (PMT) and multiwalled carbon nanotubes (MWCNT) based nanocomposites have been prepared chemically at various wt. ratios. Nanocomposites are characterized by TEM, TGA, XRD and Raman spectroscopy. The morphology of nanocomposites shows fine wrapping of PMT over MWCNT. Electrodes containing PMT nanocomposites have been prepared and p-doping of nanocomposites studied in electrolyte containing 1 M tetraethylene ammonium tetra fluroborate in propylene carbonate. Specific capacitance of the nanocomposites increases with increase in PMT loading and a maximum specific capacitance of 296 F g(-1) has been obtained for the nanocomposite with PMT/MWCNT wt. ratio of 87.5/12.5. Non aqueous based asymmetric supercapacitors containing PMT nanocomposites as the positive electrode and activated carbon (AC) as the negative electrode have been fabricated. Supercapacitor unit cells have been constructed at the optimized mass ratio of the electrodes so as to obtain maximum total specific capacitance and specific energy. Highest specific capacitance obtained for PMT nanocomposite-AC system is 38.5 F g(-1) of the total active material in the supercapacitor. The complex capacitance of the supercapacitors derived from electrochemical impedance spectroscopy reveals that supercapacitor containing nanocomposites with higher concentration of MWCNT has shorter relaxation time constant (to) leading to higher rate capability. Continuous charge-discharge cycling studies indicate that PMT nanocomposite-AC supercapacitor have better stability than bulk PMT-AC supercapacitor. (C) 2013 Elsevier Ltd. All rights reserved

A supercapacitor based on longitudinal unzipping of multi-walled carbon nanotubes for high temperature application

Multi-walled carbon nanotubes (MWCNTs) were partially unzipped longitudinally by a chemical method. Unzipped multi-walled carbon nanotubes (UZ-MWCNTs) were characterized by transmission electron microscopic analysis, X-ray diffraction and Raman spectroscopic analyses. UZ-MWCNTs were utilized for electrode preparation and the electrodes were used in the fabrication of a supercapacitor. At room temperature, the UZ-MWCNTs based supercapacitor showed a specific capacitance of similar to 41 F g(-1), while pristine MWCNTs based supercapacitor exhibited 22 F g(-1) at the scan rate of 25 mV s(-1). The increase in specific capacitance was attributed to an increase in effective specific surface area of UZ-MWCNTs due to partial unzipping. UZ-MWCNTs based supercapacitor exhibited an increase in specific capacitance with increase in temperature. It showed a specific capacitance of similar to 74 F g(-1) at 100 degrees C at the scan rate of 25 mV s(-1), while the pristine MWCNTs based supercapacitor did not show any appreciable change in specific capacitance as a function of temperature. UZ-MWCNTs exhibited three-fold increase in specific capacitance as compared to pristine MWCNTs at 100 degrees C. Impedance spectroscopic analysis of the supercapacitors revealed that the UZ-MWCNTs based supercapacitor exhibited higher internal resistance and lower leakage resistance than pristine MWCNTs based supercapacitor. Continuous 'charge-discharge' cycling behaviour indicated that the UZ-MWCNTs based supercapacitor exhibited less stability during initial cycles even though it depicted higher specific capacitance as compared to the pristine MWCNTs based supercapacitor