Hemant T. S. Phayde

Molecular transport characteristics of Santoprene thermoplastic rubber in the presence of aliphatic alkanes over the temperature interval of 25 to 70°C

Abstract Solvent transport into Santoprene thermoplastic rubber samples exposed to –alkanes (C 5 to C 16 ), 2,2,4-trimethylpentane, cyclohexane and 1,2,3,4-tetrahydronaphthalene in the temperature interval 25–70°C has been studied. For all liquids, equilibrium penetrant uptake and degree of penetrant overshoot have been influenced by factors such as penetrant size, shape, polymer morphology and temperature. Sorptio–desorptio–resorptio–redesorption experiments have been performed for some typical solvents at 25°C to determine the true sorption equilibrium and transport parameters. The values of the polymer-solvent interaction parameters have been used to calculate the molar mass between crosslinks of the network polymer. Kinetic rate constants and the activation parameters for the process of diffusion, permeation and sorption/desorption have been calculated. The transport coefficients and the activation parameters showed a dependence on the size of the penetrant molecules. The transport phenomenon was found to follow the Fickia–type mechanism.

A study of sorption/desorption profiles and diffusion anomalies of organic haloalkanes into a polymeric blend of ethylene-propylene random copolymer and isotactic polypropylene

Experimental values for sorption, desorption, resorption and redesorption processes for a polymeric blend of ethylene-propylene random copolymer and isotactic polypropylene were obtained at 25, 40, 55 and 70°C with haloalkanes using a gravimetric method. Diffusion coefficients exhibited a dependence on the type and nature of solvent molecules. In view of an increase in diffusivity with temperature, Arrhenius relation was used to estimate the energy of activation for diffusion. These results showed a dependence on polymer-solvent interactions. A numerical method based on the finite difference method was used to calculate liquid concentration profiles into polymer membranes and these results were compared with those obtained from analytical solutions of Ficks equation.

Sorption/diffusion of aliphatic esters into tetrafluoroethylene/propylene copolymeric membranes in the temperature interval from 25 to 70°C

Abstract The sorption and diffusion of seven aliphatic esters into tetrafluoroethylene/propylene copolymeric membranes have been studied by the weight gain assay method at 25, 40, 55 and 70 °C. Kinetic curves have been generated for these systems to compute diffusion and sorption coefficients. Equilibrium concentrations have been described by the first-order kinetic rate equation. The temperature dependence of the transport parameters followed an Arrhenius relationship, from which the activation energy for diffusion and permeation were calculated. Calculated results are discussed in terms of size and shape of diffusing molecules into a polymer membrane. Profiles of liquid concentrations have been calculated by solving Ficks diffusion equation and also by using a numerical method based on a finite difference method.

Molecular migration of hazardous liquids into thermoplastic ethylene-propylene random copolymer and isotactic polypropylene membranes

The molecular migration of hazardous organic halocarbons into thermoplastic polymer blend membranes has been studied using a gravimetric technique. From the sorption results, the diffusion and permeation of liquids have been calculated. Molecular migration depends on the nature of the halocarbons, membrane-solvent interactions, temperature, and availability of free volume within the membrane matrix. The size and the polarity of liquids do not show any systematic effect on sorption and desorption phenomena. The liquid migration results have been analyzed using a Fickian mechanism of sorption and diffusion. A numerical method based on the finite difference approach has been used to compute the liquid concentration profiles in the membrane materials. The estimated Arrhenius activation energy for diffusion and the heat of sorption are indicative of the nature of the liquids and their interactions with the membrane. The rate of evaporation of liquids has been calculated for sorption and desorption runs, and these results depend on the volatility of the halocarbons.

Sorption and Diffusion Profiles of Monocyclic Aromatic Liquids into Polymeric Blends of Ethylene-Propylene Random Copolymer and Isotactic Polypropylene∗

Abstract Molecular transport of monocyclic aromatics into polymeric blends of ethylene-propylene random copolymer and isotactic polypropylene is investigated in the temperature interval 25°-70°C. For all liquids, the penetrant transport rate, equilibrium penetrant uptake, and degree of penetrant overshoot are influenced by the type of the penetrant and the experimental temperature. Sorption-desorption-resorption-redesorption (S-D-RS-RD) experiments have been performed to determine the true equilibrium sorption and diffusion coefficients. These S-D-RS-RD experiments are a convenient method of determining the continuous weight loss during long-term solvent exposure, a phenomenon associated with the release of residuals. The molar mass between crosslinks of the polymer, the kinetic rate constants, and the activation parameters for diffusion, permeation, and sorption are obtained. Transport coefficients and the activation parameters are affected by the type and size of the penetrant molecules. The sorption ki...

Resistivity and dimensional stability of high-performance engineering thermoplastic blend of ethylene-propylene random copolymer and isotactic polypropylene membrane in the presence of hazardous haloalkanes

This study addresses the solvent transport characteristics of eight haloalkanes which are considered to be hazardous liquids into the engineering copolymeric blend membrane consisting of ethylene-propylene random copolymer and isotactic polypropylene. The sorption/desorption kinetic curves obtained at different temperatures have been used to estimate the diffusion coefficients of the liquids into the matrix materials. These results have been discussed in terms of physical parameters such as size of the molecule, polarity, and the structure. The liquid concentration profiles have been obtained from the analytical solutions of the Ficks equation. These curves are compared with the model simulation results based on the finite difference method. The average values of diffusion coefficients have also been calculated to investigate their dependency on concentration. Overshoot effects, activation energies for diffusion, heats of sorption, and the values of the rates of evaporation were obtained to assess the solvent resistivity and dimensional stability of the barrier polymer in application areas involving exposure to hazardous solvents.

Transport kinetics and diffusion of monocyclic aromatic liquids in polymeric blends of ethylene-propylene random copolymer and isotactic polypropylene

Abstract Experimental results of molecular transport and diffusion parameters, determined by a gravimetric method, are presented for a thermoplastic Santoprene rubber in the presence of monocyclic aromatics between 25° and 70°C. The analysis of sorption, diffusion, and activation parameters led to the conclusion that transport depends on solvent size and the chemical nature of the molecules. Overshoot effect is attributed to the complex morphology of the Santoprene. However, other factors which might induce overshooting are the polymer segment relaxation and the leaching of the indigenous additives. Transport kinetics is studied using the first-order equation. Flory-Rehner theory is used to estimate the molar mass between physical chain entanglements.

Sorption, Desorption, and Diffusion of Haloalkanes into Miscible Polymeric Blends of Ethylene-Propylene Random Copolymer and Isotactic Polypropylene

Abstract Molecular transport of haloalkanes into polymeric blend sheets of ethylene-propylene random copolymer and isotactic polypropylene, Santoprene, has been investigated gravimetrically in the temperature interval 25°-70°C. Equilibrium sorption, desorption, resorption, redesorption, and degree of penetrant overshoot were influenced by the type of haloalkane used and the experimental temperature. Diffusion coefficients have been computed for the sorption (S), desorption (D), resorption (RS), and redesorption (RD) runs. Temperature-dependent sorption and diffusion coefficients were analyzed using the Arrhenius relation. Santo-prene-haloalkane interactions have been discussed in terms of sorption, desorption, and diffusion coefficients.