Shivaputrappa B. Harogoppad

Pervaporation Separation of Organic-Aqueous and Organic-Organic Binary Mixtures

Abstract In recent years membranes and membrane-related processes have gained much importance in several areas of science and technology. Intensive research activity has been pursued in this area all over the world in the past three decades. Among several membrane-related processes, the pervaporation (PV) technique is well known and has been used to separate mixtures of low molecular weight close-boiling organic liquids, aqueous-alcohol mixtures, and so on. Contrary to other membrane processes such as hyperfiltration and ultrafiltration, a phase transition occurs during the PV process. Consequently, the energy input of the process is at least equal to the heat of vaporization of the permeating liquids. This technique was first developed in the Research Center of the American Oil Company in Texas in the 1950s [1, 2], although the term was coined in 1917 by Kober of the New York State Department of Health at Albany. The technique has regained much attention since the early 1980s owing to membrane and proces...

Interactions of substituted benzenes with elastomers

Abstract The effects of polymer structure and penetrant molecular size on sorption and diffusion of substituted benzenes (aromatics) with commercial elastomers such as neoprene, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, nitrile-butadiene rubber and natural rubber have been investigated in the temperature interval of 25–60°C. The rate-of-sorption behaviour deviates from the Fickian mechanism. The equilibrium sorption of the sorbents decreases linearly with increasing penetrant molecular size. At about 55–60 mol% uptake, the sorbed concentration levels off. Diffusion coefficients decrease with increasing molecular weight of the penetrants. It is suggested that the hindered chain segmental motion contributes to the overall sorption in addition to strictly thermodynamic considerations. Free-volume concepts can be used to explain the diffusion mechanism through rubbery polymers. Effective values of the molar mass between crosslinks computed from the Flory-Rehner theory appear to vary widely with different liquids and elastomers.

RUBBER-SOLVENT INTERACTIONS

Abstract A thorough understanding of the structure physical/mechanical properties of the polymers has made possible the molecular design of macromolecules for specific application needs. Several methods exist for polymer synthesis and processing. When it concerns homopolymers, each polymer structure is identified with a particular method for its realization. Depending upon the situation, one or more of the methods (polycondensation, cationic, anionic, or free radical technique) is sometimes resorted to. Each process has its own merits and demerits. The condensation method is applicable to only a few cases of condensation monomers. A variety of vinyl and cyclic monomers are polymerized by anionic and cationic processes. These processes have obvious disadvantages in the sense that they warrant rigorous polymerization conditions like the need for ultrapure monomers, absolute moisture/oxygen free atmosphere, and cryogenic temperatures which are often difficult to realize on an industrial scale. A recent trend...

Sorption and transport of aqueous salt solutions of acetates, acetic and monochloroacetic acids in polyurethane

Abstract Sorption, diffusion and permeation of aqueous salt solutions of acetates of sodium, calcium and nickel in addition to acetic and monochloroacetic acid solutions have been investigated in the temperature interval of 25–60°C in a commercial polyurethane. An immersion/weight-gain experiment was used to study sorption and diffusion of 0.15, 0.5 and 1.0 M solutions of acids and salts. Permeability coefficients were estimated from sorption and diffusivity coefficients. From the temperature dependence of transport coefficients, the Arrhenius activation parameters have been estimated and the results were used in the discussion of transport mechanisms. The diffusivity of monochloroacetic acid solution was smaller but its solubility was higher than all the solutions used in this research. For comparative purposes, the transport of water was also studied.

Diffusion and Sorption of Organic Liquids Through Polymer Membranes. III. Polyurethane, Neoprene, SBR, EPDM, NBR, and Natural Rubber Versus Cyclic Compounds, Esters, and Hydrocarbons

Abstract Diffusion and sorption of a variety of organic liquids into six engineering polymers have been investigated over the interval of 25°–60°C by the use of a conventional weight-gain experiment. While the method is laborious and time consuming, it yields reliable diffusion data. The transport mechanism depends, to a great extent, on the type of the solvent molecule and the barrier material. In all the polymer-solvent systems, the activated diffusion mechanism is operative and that the Arrhenius parameters of diffusion prove the conventional wisdom that smaller diffusion coefficients and higher activation energies are observed for the bigger solvent molecules. The diffusion mechanism has been classified to be anomalous. Sorption equilibrium data have been used to estimate the polymer-solvent interaction parameter in addition to molar mass between crosslinks and other thermodynamic quantities such as enthalpy and entropy of sorption. A first-order kinetic model appears to explain satisfactorily the tra...

Polarizability and molecular radius of bromoform and hydrocarbon liquids

Abstract Aminabhavi, T.M., Aralaguppi, M.I., Harogoppad, S.B. and Balundgi, R.H., 1992. Polarizability and molecular radius of bromoform and hydrocarbon liquids. Fluid Phase Equilibria, 72: 211-225. Densities and refractive indices of bromoform, n -heptane, n -octane, 2,2,4-trimethylpen- tane, n -nonane, n -decane, n -tetradecane, n -hexadecane and 1,2,3,4-tetrahydronaphthalene have been measured over the temperature interval of 298.15-323.15 K. Polarizabilities and molecular radii were calculated on the basis of Bottchers theory of electric polarization and compared with the molecular radii evaluated from the molar volumes of the liquids and from free volume considerations. Bottchers theory is found to be satisfactory in estimating the molecular radii and polarizability of long-chain molecules. Lorenz-Lorentz and Eykman relations have been used to calculate the thermal expansion coefficients and the polarizabil- ities of liquids.