K.A. Dubey

Electron Beam Grafted Polymer Adsorbent for Removal of Heavy Metal Ion from Aqueous Solution

Abstract An electron beam grafted adsorbent was synthesized by post irradiation grafting of acrylonitrile (AN) on to a non‐woven thermally bonded polypropylene (PP) sheet using 2 MeV electron beam accelerator. The grafted poly(acrylonitrile) chains were chemically modified to convert a nitrile group to an amidoxime (AMO) group, a chelating group responsible for metal ion uptake from an aqueous solution. The effect of various experimental variables viz. dose, dose rate, temperature, and solvent composition on the grafting extent was investigated. PP grafted with the amidoxime group (AMO‐g‐PP) was tested for its suitability as an adsorbent for removal of heavy metal ions such as Co2+, Ni2+, Mn2+, and Cd2+ from aqueous solution. Langmuir and Freundlich adsorption models were used to investigate the type of adsorption of these ions. The adsorption capacities of the adsorbent for the metal ions were found to follow the order Cd2+>Co2+>Ni2+>Mn2+. The kinetics of adsorption of these ions indicated that the rate of adsorption of Cd2+ was faster than that of other ions studied.

Polychloroprene rubber/ethylene-propylene diene monomer/multiple walled carbon nanotube nanocomposites: synergistic effects of radiation crosslinking and MWNT addition

Synergistic effect of MWNT induced reinforcement and high energy radiation induced crosslinking on the physico-mechanical and thermal characteristics of polychloroprene rubber (PCR)/ethylene-propylene diene rubber (EPDM)/MWNT elastomeric nanocomposites was investigated. The extent of reinforcement, as assessed using the Kraus equation suggested high reinforcement of the blend on MWNT addition; though, the thermal stability and glass transition of the PCR and EPDM components were not significantly affected by MWNTs. The elastic modulus increased with the radiation dose as well as with the increase in MWNT content. The reinforcing mechanism of the nano-composites was studied by various micromechanics models all of which predicted higher moduli than the experimentally observed results, indicating agglomeration in the nano-composites. Nevertheless, in all the composites synergistic effect of radiation crosslinking and MWNT induced reinforcement were seen, suggesting radiation induced crosslinking between polymer and MWNT interface.

Correlation between surface energy and uptake behavior of radiation-grafted methacrylic acid-g-LDPE

An efficient and low-cost effluent adsorbent has been developed by grafting an ionizable monomer onto polyolefin surface and its efficacy was tested for dyes and metal ion uptake from aqueous medium. The grafted matrix was synthesized by optimizing various experimental parameters such as irradiation dose, dose rate, monomer concentration, inhibitor concentration, surfactant concentration, and backbone thickness. Grafting yield decreased with dose rate and thickness and increased with the concentration of methacrylic acid and inhibitor. Grafting kinetics studies indicated that grafting rate is comparatively much affected by dose rate that monomer concentration. Surface energy of the grafted surface was accessed from dynamic contact angle measurements. Uptake study of Basic Red 29, Methylene Blue showed high correlation with grafting yield and polar component of the surface energy; however, metal ion uptake was exceptionally high at ~25 grafting (%), highlighting anomalous behavior of MAA-g-LDPE with respect to surface energy and total ion uptake capacity.

Radiation Processed Styrene-Butadiene Rubber/Ethylene-Propylene Diene Rubber/Multiple-Walled Carbon Nanotubes Nanocomposites: Effect of MWNT Addition on Solvent Permeability Behavior

Different compositions of SBR/EPDM 50:50 blends containing multiple-walled carbon nanotubes (MWNT) as nanoparticulate fillers (0.5%–10%) were evaluated for radiation sensitivity and solvent permeability. The efficiency of radiation ***cross-linking was analyzed by gel-content and Charlesby–Pinner parameter measurements. ***Gamma-radiation-induced cross-linking extent was found to increase with radiation dose and MWNT concentration, which was reflected in different extents of swelling. Rigorous analysis of swelling and diffusion data, on the basis of the transport exponent (n) values and diffusion/relaxation rate indicated anomalous diffusion behavior for most of the nanocomposites. The swelling extent in different solvents was found to be a function of polymer-solvent interaction as well as stearic hindrance due to the structure/size of the solvent molecules. Polymer-filler interaction investigated by a Kraus plot indicated high reinforcement of the SBR/EPDM matrix on MWNT addition. There was no significant change in surface energy or hydrophilicity of the SBR/EPDM matrix on introduction of MWNT into it.

Swelling response of radiation synthesized 2-hydroxyethylmethacrylate-co-[2-(methacryloyloxy)ethyl] trimethylammonium chloride hydrogels under various in vitro conditions.

High-energy 60Co gamma radiation has been used to synthesize 2-hydroxyethylmethacrylate-co-[2-(methacryloyloxy)ethyl]trimethylammonium chloride (HEMA-co-MAETC) polyelectrolyte hydrogels. HEMA-co-MAETC co-polymer gels were characterized and investigated for swelling behaviour in different swelling conditions. Fourier transformed infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) techniques were used to characterize the co-polymer gels. Swelling extent of the gels was found to be a linear function of MAETC content in the gels. The effect of ionic strength, temperature, pH, some solutes of biological importance like glucose, urea, and surfactants such as Triton-X and deoxycholic acid on swelling behavior have been reported. The swelling of gels at higher temperature enhanced the swelling rates but not the swelling extent. HEMA-co-MAETC hydrogel exhibited an excellent responsive characteristic to the ionic strength of the swelling medium. It was found that the swelling of the co-polymer gel at 60°C reduced the swelling–deswelling cycle time by approx. 30% without altering the swelling extent. The gels were also investigated for their swelling in aqueous solutions of anionic dyes, acid blue 25 (AB25), acid blue (AB74) and acid yellow 99 (AY99), and were found to be suitable for dye uptake applications.

Morphology, rheology and biodegradation of oxo-degradable polypropylene/polylactide blends

Abstract The blends of polypropylene (PP)/polylactide (PLA) with or without compatibilizer, and with pro-oxidant (cobalt stearate/calcium stearate) and pro-oxidant filled PP were prepared by using the melt blending technique. Films of these blends were prepared by compression molding. PP85PL15 and PP85PL15MA4 were the optimum blends from the tensile strength point of view. The improvement in the tensile strength of PP85PL15MA4 blend was achieved by addition of 4 phr compatibilizer. Cobalt stearate and calcium stearate were added separately to PP85PL15MA4 blend in 0.2% (w/w) ratio. The optimized blends were further characterized by differential scanning calorimetry, X-ray diffraction, rheological studies, scanning electron microscopy (SEM) and biodegradability test. Rheological studies confirmed the pseudo-plastic nature of all the blend samples. SEM studies have revealed that the addition of PLA in PP85PL15 enhances the void and roughness on the blend. All the prepared blends have biodegraded in the composting environment and the blend containing pro-oxidant biodegraded to the maximum extent.

Polymers, Blends and Nanocomposites for Implants, Scaffolds and Controlled Drug Release Applications

Polymer blends and nanocomposites are widely explored for different biomedical applications such as biodegradable scaffolds, biosensors, implants and controlled drug release. Both, synthetic and semi-synthetic polymers are used in medical applications and have their inherent advantages and disadvantages. Synthetic polymers offer flexibility of varying monomer unit, molecular weight, branching and thus offer a diverse set of physico-mechanical properties, whereas natural polymers offer superior biocompatibility and biodegradation profile. Availability of polymer blending techniques adds another dimension to the property set that polymers can offer, and therefore polymer blending is often used to tailor biodegradability and physico-mechanical properties. Polymers, in general, have poor mechanical properties when compared to metals and ceramics, putting a load bearing limit on polymer-based medical implants. The addition of reinforcing/functional filler is expected to overcome such disadvantages of polymers. Polymers composites are heterogeneous systems wherein polymers are compounded with micron or nano-size particles to render high strength, electrical conductivity or any other functional attribute. This chapter describes the technological aspects of polymer blends and nanocomposites with a specific reference to synthesis, characteristics and applications of multi-phasic polymer systems as implants, scaffolds, and controlled drug release matrices. A detailed account of synthetic and natural polymer nanocomposites along with a brief discussion on important nano-fillers used in medical applications and interface modification techniques is presented. Few examples of recently explored novel polymer blends and composites that displayed promising properties as implants, scaffolds, biosensors and control release matrices have also been discussed.

Melt-compounded composites of ethylene vinyl acetate with magnesium sulfate as flexible EPR dosimeters: Mechanical properties, manufacturing process feasibility and dosimetric characteristics

Novel polymeric composites for radiation dosimetry were developed. The composites were prepared by solvent-free melt compounding of ethylene vinyl acetate (EVA) (40% vinyl) and magnesium sulfate (MgSO4). Mechanical properties, melt flow characteristics and dosimetric properties were investigated. The composites with up to 50% (wt) of MgSO4 were flexible and capable of flow. The dose response of the EPR signal of the composites was studied in the dose range 3Gy-4kGy and found to be linear between 18Gy and 4kGy. The reproducibility of dose measurements was good. The signal fading rate and the energy dependence of the dose response were found to be acceptable.

Thermo-oxidative degradation kinetics of grafted polypropylene films

ABSTRACT The thermo-oxidative stability and degradation behavior of polypropylene (PP) and grafted PP have been investigated using thermogravimetric analysis. Three multiple heating rate methods, namely Kissinger, Kim–Park and Flynn–Wall have been used to calculate the activation energy as a function of the extent of degradation. The four different heating rates (5, 10, 15 and 20°C/min) were maintained in the temperature range of 30–550°C during the analysis. Fourier transform infrared spectroscopy has confirmed the presence of carboxylic group on the surface of grafted PP films. Differential scanning calorimetry has shown that the crystallinity decreased with the increase in grafting. In the air atmosphere, the thermo-oxidative degradation occurs via a pathway that involves decomposition of polymer peroxide. Thermo-oxidative stability of grafted PP films is found to increase with an increase in the degree of grafting (DG). The degradation kinetic parameters were used to predict the lifetime of PP and grafted PP films. The activation energy and lifetime of grafted PP films increased with an increase in the DG. The lifetime of PP and grafted PP decreased with an increase in degradation temperature.

Improvement in thermoelectric power factor of mechanically alloyed p-type SiGe by incorporation of TiB2

Nearly 60% of the world’s useful energy is wasted as heat and recovering a fraction of this waste heat by converting it as useful electrical power is an important area of research[1]. Thermoelectric power generators (TEG) are solid state devices which converts heat into electricity. TEG consists of n and p-type thermoelements connected electrically in series and thermally in parallel[2]. Silicon germanium (SiGe) alloy is one of the conventional high temperature thermoelectric materials and is being used in radio-isotopes based thermoelectric power generators for deep space exploration programs.Temperature (T) dependence of thermoelectric (TE) properties of p-type SiGe and p-type SiGe-x wt.%TiB2 (x=6,8,10%) nanocomposite materials has been studied with in the temperature range of 300 K to 1100 K. It is observed that there is an improvement in the power factor (α2/ρ) of SiGe alloy on addition of TiB2 upto 8 wt.% that is mainly due to increase in the Seebeck coefficient (α) and electrical conductivity (σ) of...