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Mandal S.,Defence Materials and Stores Research and Development Establishment DMSRDE | Alam S.,Defence Materials and Stores Research and Development Establishment DMSRDE
Materials Research Innovations | Year: 2013

In the present study, the mechanical and thermal properties of the nanocomposites of optimised poly(ether ether ketone) (PEEK) and poly(ether ketone) (PEK) blend incorporated with nano-barium titanate (nano-BT) were investigated. The optimised blend was based on the mechanical and thermal properties of PEEK and PEK in the ratio of 80:20. Nanoparticles were incorporated into the optimised blend with the help of a twin screw extruder. The concentration of nano-BT was varied from 2 to 6 wt-%. The crystallinity of the nanocomposites was calculated using differential scanning calorimetry method. With the increase in the nanosized BT concentrations, the tensile strength, tensile modulus and impact strength increased while the elongation at break and crystallinity decreased. The crystallinity of the nanocomposites influenced the elongation at break. Morphological studies were carried out using SEM. The nanocomposites were evaluated using the theoretical predictive model known as 'Pukanszky model' applicable to the tensile strength of the nanocomposites. © 2013 W. S. Maney & Son Ltd.


Dhanalakshmi J.P.,k-Technology | Alam S.,Defence Materials and Stores Research and Development Establishment DMSRDE | Vijayakumar C.T.,k-Technology
High Performance Polymers | Year: 2013

The compound bispropargyl ether of bisphenol-A (BPEBPA) is prepared using phase transfer catalyst. Different copper salts like cuprous chloride (CuCl), cupric chloride dihydrate (CuCl2.2H2O), copper sulphate pentahydrate (CuSO4.5H2O), basic copper carbonate (CuCO3.Cu(OH) 2), cupric acetate monohydrate ((CH3COO)2Cu.H2O), and cupric oxide (CuO) are blended separately with BPEBPA (1%, w/w) and the curing characteristics of these materials are investigated using differential scanning calorimetry (DSC). The presence of copper salt in BPEBPA shifts the curing temperature to a lower temperature region. The materials are thermally cured and the structural characterisation and the thermal properties of these cross-linked materials are investigated using Fourier-transform infrared (FTIR) spectrophotometer and thermogravimetric analyzer (TGA). Of the different copper salts investigated, the presence of copper sulphate pentahydrate in BPEBPA increases the thermal stability of the cured BPEBPA. The thermal degradation products of thermally cured pure BPEBPA and copper salts containing BPEBPA are studied using TG-FTIR. The phenols, substituted phenols, carbon monoxide (CO), carbon dioxide (CO2), and alkenes are major volatiles evolved during the thermal degradation of these materials. © The Author(s) 2012.


Vijayakumar C.T.,k-Technology | Surender R.,k-Technology | Rajakumar K.,k-Technology | Alam S.,Defence Materials and Stores Research and Development Establishment DMSRDE
Journal of Thermal Analysis and Calorimetry | Year: 2011

The compound 2,2-bis[4-(4-maleimidophenoxy phenyl)]propane was prepared by the imidization of bisamic acid of 2,2-bis(4-aminophenoxy phenyl)propane. Various nanoclays were blended with this bismaleimide and thermally cured. The structural characterization of the synthesized materials and the thermal properties of the bismaleimide and their blends were investigated through FTIR, 1H and 13C NMR, differential scanning calorimetry and thermo gravimetric analysis. Among the various clays investigated, Cloisite 15A shows strong influence on the cure exotherm of bismaleimide. Introduction of clay mineral into bismaleimide shifts the onset of curing exotherm to higher temperature and is nearly 40 °C. The thermal stability of the clay loaded cured bismaleimide increases and the presence of clay particles in the cured bismaleimide matrix enhances the char formation. © 2010 Akadémiai Kiadó, Budapest, Hungary.


Katiyar R.,H+ Technology | Bag D.S.,Defence Materials and Stores Research and Development Establishment DMSRDE | Nigam I.,H+ Technology
International Journal of Chemical Kinetics | Year: 2011

Radical copolymerization of fullerene (C60) and n-butyl methacrylate (BMA) has been carried out using triphenylbismuthonium ylide as an initiator at 70°C for 4 h in a dilatometer under nitrogen atmosphere. The kinetic expression of the polymerization is Rpα [Ylide] 0.5[C60]-1.0[BMA]1.2, which is similar to that expected for ideal kinetics. The rate of polymerization increases with an increase in the concentration of initiator and BMA. However, it decreases with an increase in the concentration of fullerene. Fullerene acts as radical scavengers causing retardation in polymerization. The activation energy of copolymerization was estimated to be 72.2 K J mol-1. The fullerene-containing BMA copolymers were characterized by FTIR, 1H NMR, 13C NMR, UV-vis, and GPC analyses. © 2011 Wiley Periodicals, Inc.


Ramani R.,Defence Materials and Stores Research and Development Establishment DMSRDE | Alam S.,Defence Materials and Stores Research and Development Establishment DMSRDE
High Performance Polymers | Year: 2014

In the present study, the effect of P-EPQ, an organophosphonite antioxidant, on the glass transition and the viscoelastic behavior of optimized poly(ether ether ketone) (PEEK)/poly(ether imide) (PEI; PEEK/PEI: 50/50) blend has been reported. For this, P-EPQ was added in various proportions to the PEEK/PEI blend and was studied by quasi-isothermal modulated differential scanning calorimetry (Qi-MDSC) and dynamic mechanical thermal analysis (DMTA) methods. The Qi-MDSC results clearly indicate a significant decrease in the glass transition temperature of the blend up to 1 wt% P-EPQ addition. The DMTA measurements revealed a decrease in tan δ peak temperature upon antioxidant addition in agreement with calorimetric results. The shift factors obtained using the time-temperature superposition of DMTA data exhibit Williams-Landel-Ferry behavior, and the fractional free volume of the blend increases with increase in antioxidant addition (up to 1 wt%). The "master curve" of storage modulus predicts high modulus for the blend with 1 wt% antioxidant, revealing its suitability for high-impact applications. © The Author(s) 2013.


Ramani R.,Defence Materials and Stores Research and Development Establishment DMSRDE | Alam S.,Defence Materials and Stores Research and Development Establishment DMSRDE
Journal of Applied Polymer Science | Year: 2012

Blends of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) were examined for their miscibility at the nanoscopic level using positron annihilation lifetime spectroscopy (PALS) and modulated differential scanning calorimetry (MDSC). The free volume results obtained from PALS reveal that PEEK and PEI exhibit high degree of miscibility showing interlamellar segregation when the PEI content in the blend is ≥50%. Although the average free volume sizes of PEEK and PEI are nearly same, a clear distinction could be made from their size distribution. The free volume of PEI is found to be narrow as compared with PEEK. Also, herein, we provide the first evidence of the influence of interlamellar segregation on the free volume distribution in a polymer blend. The crystalline structure of the blend was studied by X-ray scattering and the surface morphology was examined by scanning electron microscopy (SEM). The MDSC results indicate the presence of a possible rigid amorphous fraction (RAF) and corroborate the positron lifetime and X-ray scattering results. © 2012 Wiley Periodicals, Inc.


Katiyar R.,H+ Technology | Bag D.S.,Defence Materials and Stores Research and Development Establishment DMSRDE | Nigam I.,H+ Technology
Thermochimica Acta | Year: 2013

In this investigation, thermal properties of fullerene (C60) containing poly(alkyl methacrylate)s have been studied. The glass transition temperatures (Tg) and thermal stability of C60 containing poly(methyl methacrylate) (FMMA) and poly(n-butyl methacrylate) (FBMA) were more than that of the corresponding virgin polymers and the values increased with the increasing fullerene content in such polymers. Chemically linked bulky fullerene imparts chain rigidity and hence restricts segmental motion causing higher Tg values for C60 containing polymers than that of the polymers without fullerene. Thermal degradation of C60 containing poly(alkyl methacrylate)s is hindered prominently due to the presence of fullerene which scavenges the macroradicals formed during polymer degradation. The mechanism of thermal degradation of C60 containing poly(alkyl methacrylate)s is, therefore, associated mainly with three types of reactions: (a) end chain scission, (b) random chain scission and (c) reaction of fullerene (C60) with macroradicals obtained in thermal degradation process. © 2013 Elsevier B.V.


Bag D.S.,Defence Materials and Stores Research and Development Establishment DMSRDE | Rao K.B.,Defence Materials and Stores Research and Development Establishment DMSRDE
Polymer International | Year: 2010

The aim of this investigation was the copolymerization of a chiral monomer, (R)-N-(1-phenylethyl) methacrylamide, with an achiral monomer, 2-hydroxyethyl methacrylate (HEMA). The copolymerization characteristics as well as the chiroptical properties (optical rotation and circular dichroism) and their variation with copolymer composition and temperature are discussed. The copolymers are statistical and enriched in HEMA. The monomer reactivity ratio of the chiral monomer (r1) is 0.133 whereas that of HEMA (r2) is 1.042 based on the Kelen-Tudosmethod. The sequence of consecutive chiral monomer units predominates for a feed composition between 0.5 and 0.9 (mole fraction). On the other hand, the sequence of HEMA is uniform and it predominates for a feed composition of around 0.5 (mole fraction). The chiroptical properties of the copolymers do not vary linearly with the content of chiral units in the copolymers. Theoptical rotation andcircular dichroism attainoptimumvalues above 30-40 mol%of chiralmonomerunits in the copolymers.However, the circulardichroism of the copolymers varies linearly with the temperature. The chiral monomer being a more bulky structure is less reactive than HEMA. The nonlinear variation of chiroptical properties of the copolymers with the content of chiral units may be due to the secondary interaction in the copolymers associated with the hydrogen bonding involving the amide linkage (CONH) present in the pendant chromophore of the chiralmonomer as well as the hydroxyl pendant group of HEMA and also the aromatic π-π interaction. © 2009 Society of Chemical Industry.


Mukhopadhyay K.,Defence Materials and Stores Research and Development Establishment DMSRDE | Bhasker Rao K.U.,Defence Materials and Stores Research and Development Establishment DMSRDE
Advanced Science Letters | Year: 2010

Carbon fiber based carbon micro-flowers were produced using catalytic chemical vapour deposition technique on reproducible basis using specially designed nickel sulphide catalyst powder. The purity of the product is ~95% as revealed by thermal analysis. Scanning electron microscopy analysis also confirms the absence of any impurities (e.g., amorphous carbon). Surface area analysis reveals a large surface area in the range 300-400 m 2/gm with adsorption average pore diameter ~5 nm. Possible uses are proposed. © 2010 American Scientific Publishers.


Khanam A.,Defence Materials and Stores Research and Development Establishment DMSRDE | Tripathi S.K.,Defence Materials and Stores Research and Development Establishment DMSRDE | Roy D.,Defence Materials and Stores Research and Development Establishment DMSRDE | Nasim M.,Defence Materials and Stores Research and Development Establishment DMSRDE
Colloids and Surfaces B: Biointerfaces | Year: 2013

A new type of fluorescent carbon based nanomaterial has drawn considerable attention due to their unique physicochemical properties. Carboxyl functionalized carbon nanoparticles are well documented in the literature. However, the carbonyl moiety in the carboxyl group considerably reduces the photoluminescence quantum yield. In this study, we present a direct, simple and novel synthetic route to produce hydroxyl functionalized fluorescent carbon nanoparticles derived from candle soot using organic base and surfactant which could be readily scaled up. The functionalization of carbon nanoparticle was confirmed by various spectroscopic techniques. 1H NMR and FTIR measurements have been used to confirm the presence of sp2 carbon in the form of aryl and hydroxyl moieties. MALDI-TOF Mass and TGA measurements further confirmed the functionalization. Structural characterization of these particles by Raman spectroscopy showed characteristic peaks located at 1333 and 1583cm-1 corresponding to diamond-like (D) and graphite-like (G) bands of the carbon allotropes respectively. The minimum grain size of 7.3nm was calculated using Raman spectra of the functionalized carbon nanoparticles which corroborate well with the results of dynamic light scattering (DLS) and TEM studies. UV-vis spectroscopic measurements displayed an absorption band at ca. 245nm, which was consistent with the optical characteristics of functionalized carbon nanoparticles. PL measurements confirmed that the functionalized carbon nanoparticles have characteristic emission peak and shows fluorescence under blue light excitation. With a combination of free dispersion in water and attractive PL properties, these functionalized carbon nanoparticles hold promise for application in nanotechnology. © 2012 Elsevier B.V.

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