Virendra Kumar Gupta

The Preparation of Polymer/Silver Nanocomposites and Application as an Antibacterial Material

An elegant and facile route for the preparation of polymer/silver nanocomposites for polymers having solubility in organic solvents has been developed. Aqueous colloidal solution of nano-silver has been used as the source of nano-silver particles. Nano-silver particles were transferred to the poly(methyl acrylate) (PMA) solution in chloroform using phase transfer methodology. Separation of the aqueous phase gave solution of nano-silver/PMA in chloroform. The solution was coated onto glass substrate providing uniform film of antibacterial PMA/silver nanocomposite, thus exhibiting its potential application as a coating material. The same methodology has been successfully extended to prepare polyether sulphone/silver nanocomposites.

Effect of Donors on the Activation Mechanism in Ziegler–Natta Catalysis: A Computational Study

Full quantum chemical calculations, using density functional theory (DFT), have been conducted to explain the effect of donors on the “activation mechanism” in the Ziegler–Natta (Z–N) catalyst system. In the activation mechanism, the inactive TiIVCl4 catalyst converts into the active TiIIICl2Et catalyst with the help of the AlEt3 present in the system. The donors that have been considered in this study are: ethyl benzoate (eb), two representative diether cases, a phthalate donor, and a silyl ester donor. The results indicate that eb and the diether donor cases donor have a negative effect on the barriers for the activation mechanism. However, the eb donor can be displaced from the MgCl2 surface by AlEt3, which matches experimental observations. For the phthalate, silyl ester and TiCl3–OC4H8Cl cases, the results indicate that a significant induction period would be present in Z–N systems employing such donors or having such a catalytic center, before catalysis could commence.

Morphology Controlled Magnesium Ethoxide: Influence of Reaction Parameters and Magnesium Characteristics

Controlled reaction of magnesium with ethanol was found to produce morphological magnesium ethoxide. The scanning electron microscopy studies indicate that particles of magnesium ethoxide grow on the surface of magnesium granules and are detached from the surface as a result of shearing and collisions during the reaction. Particle characteristics of magnesium show influence on the kinetics of the reaction as well as morphological characteristics of magnesium ethoxide. Impact of other process parameter variations on the magnesium ethoxide particle characteristics is also studied. The reaction rate, agitation speed, and type of agitator show influence on the product characteristics, whereas no influence of change in reaction pressure is observed.

Polypropylene Resin Flowability Improvement Through Catalyst Morphology

The phenomenon of replication of morphology from Zeigler-Natta catalyst to polypropylene resin has been established leading to enhanced resin flowability with the use of spherical morphology catalyst. PP resin obtained using catalyst with varying morphological characteristics in terms of particle shape and size distribution was subjected to flowability analysis. Flowability aspects of PP resin have been quantified and correlated with the catalyst circularity. Morphology controlled spherical catalyst yields better polypropylene resin in terms of uniformity in shape and size distribution. The same gets reflected in the form of low angle of repose and better flowability of the resin.

Morphological silica-supported acid catalyst for esterification of aliphatic fatty acid

Abstract Silica-supported acid catalysts were synthesized and characterized for composition, morphology, particle size distribution, and crystallinity. The catalysts are used for the esterification of long-chain aliphatic acids with alcohol to produce the corresponding ester. Process parameters such as time, temperature, and solvent ratio influence the conversion of fatty acid to ester. A supported catalyst was found to show higher catalytic activity as compared to the conventional sulfuric acid catalyst.

Stabilized polypropylene synthesis using supported titanium catalyst system in presence of phenolic compounds

Stabilized polypropylene synthesis is carried out using supported titanium catalyst system in presence of phenols. The effect of phenolic compounds such as 2,2′-methylenebis(4-tert-butyl-6-methylphenol) (PH1) and 4,4′-methylenebis(2,6-di-tert-butylphenol) (PH2) is studied on the productivity and stereospecificity of catalyst system as well as on molecular weight characteristics. The extent of stabilization of PP resin by phenolic compounds for oxidative degradation is determined by measurement of oxygen induction time. Molecular weight and b color change are also investigated before and after thermal aging. The catalyst productivity was found to be unaffected by the concentration of phenolic compounds in the studied range. The thermal stability of the polymer resin is, however, found to be dependent on the nature of phenolic compound. The masked PH1 phenolic compound showed better antioxidant characteristic as compared to PH2.

Titanium Complexes of Tartarate for Ethylene Polymerization

Titanium complexes of tartarate were synthesized by complexation of titanium tetrachloride with tartarate. The isolated products were characterized by compositional, infrared and thermogravimetric analysis. Synthesized complexes in combination with methylaluminoxane as cocatalyst polymerize ethylene to produce high‐density polyethylene. The efficiency of catalysts is found to be dependent on polymerization parameters and nature of cocatalyst. The polyethylene was characterized for melting temperature and molecular weight characteristics by DSC and GPC, respectively.

Synthesis of long chain aliphatic ester and its titanium complexes for ethylene polymerization

Abstract Long chain aliphatic ester, isopropyl myristate, was synthesized using energy efficient microwave irradiation technique. The iso propyl myristate forms complexes with titanium tetrachloride in different mole ratios. The nature of chemical bonding between the titanium and the ester functionality was investigated by FTIR and NMR spectroscopy. The performance of synthesized complexes with methylalumoxane as co-catalyst for ethylene polymerization was found to depend on the nature of complex and polymerization parameters. Molecular weight and thermal characteristics of polyethylene was also investigated.