Interfacial Tension of Some Newtonian and non-Newtonian Fluids by the Drop-Weight Method

Experimental data on interfacial tension of 42 binary liquid-liquid systems using water, aqueous glycerol, aqueous polymeric solutions of polyvinylpyrrolidone (PVP), poly(ethylene oxide) (PEO), carboxymethyl cellulose (CMC) and polyacrylamide (PAM) as continuous phase, and carbon tetrachloride, chlorobenzene, bromobenzene, nitrobenzene, nitrotoluene and ethyl chloroacetate as dispersed phase at 20 °C are reported. The interfacial tension has been measured using the drop-weight method at different compositions of continuous phases

Structural Parameters and Swelling Behavior of pH Sensitive Poly(acrylamide-co-acrylic acid) Hydrogels

In the present work, hydrogels based on acrylamide (AAm) and acrylic acid (AAc), crosslinked with N,N’-methylenebisacrylamide (MBAAm) were prepared by free radical polymerization in solution. The effect of initial AAm/AAc mole ratio and nominal crosslinking ratio (moles of crosslinking agent/moles of polymer repeat unit) on the dynamic and equilibrium swelling behaviour of hydrogels was investigated. Hydrogels were characterized by the polymer volume fraction in the swollen state (ν2,s ), the number average molecular mass between crosslinks (Mc ) and the mesh size (ξ). The swelling capacity of hydrogels was found to decrease with increasing nominal crosslinking ratio. The results show a significant influence of AAc monomer concentration on swelling behavior of poly(acrylamide-co-acrylic acid) hydrogels. Hydrogels containing higher acrylic acid content had a higher equilibrium mass swelling at pH 7.4 and in distilled water than at pH 3.0 where the acrylic acid is present in nonionized state. Further, swelling data was fitted to various models and model parameters were evaluated using regression technique. Model analysis indicated that the swelling transport followed non-Fickian mechanism. Scanning electron microscopy (SEM) revealed the macroporous surface morphology of the matrix with pore size varying between 2–64 microns depending on the amounts of AAc in the hydrogel

Sorption and Drug Release Studies from Semi-interpenetrating Polymer Networks of Chitosan and Xanthan Gum

Hydrogel films of Chitosan (CS) and Xanthan gum (XA) of compositions 100/0, 90/10, 80/20, 70/30, 60/40 and 50/50 (w/w) % were prepared and swollen in simulated gastric fluid (SGF) of pH 1.2 and simulated intestinal fluid (SIF) of pH 7.4. To impart stability in acidic environment, semi-interpenetrating polymer network (semi-IPNs) films were formed using glutaraldehyde (GA) as the crosslinking agent. With increase in XA concentration, equilibrium degree of swelling reduced in SGF as well as SIF indicating maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The swelling data was observed to follow second order kinetics. Spectroscopic and thermal analyses of these semi-IPN films also suggest maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The potential of using 50/50 semi-IPN in drug delivery was studied using amoxicillin. In-vitro drug release studies indicated higher drug release in SGF than in SIF suggesting dependence of amoxicillin release kinetics and diffusion coefficient on pH of the environment and drug loading. The results suggest that CS-based semi-IPNs with different crosslinker and XA concentration could be promising candidates for formulation in oral gastrointestinal delivery systems

Magneto Binary Nanofluid Convection in Porous Medium

The effect of an externally impressed magnetic field on the stability of a binary nanofluid layer in porous medium is considered in this work. The conservation equations related to the system are solved using normal mode technique and Galerkin method to analyze the problem. The complex expressions are approximated to get useful results. Mode of heat transfer is stationary for top heavy distribution of nanoparticles in the fluid layer and top heavy nanofluids are very less stable than regular fluids. Oscillatory motions are possible for bottom heavy distribution of nanoparticles and they are not much influenced by properties of different nanoparticles. A comparative analysis of the instability of water based nanofluids with metallic (Cu, Ag) and semiconducting (TiO2, SiO2) nanoparticles under the influence of magnetic field is examined. Semiconducting nanofluids are found to be more stable than metallic nanofluids. Porosity destabilizes the layer while solute difference (at the boundaries of the layer) stabilizes it. Magnetic field stabilizes the fluid layer system significantly

Kinetics of the Esterification Reaction between Pentanoic Acid and Methanol Catalyzed by Noncorrosive Cation Exchange Resin

Methyl pentanoate, commonly known as methyl valerate, is the methyl ester of pentanoic acid (valeric acid) with a fruity odour. Methyl pentanoate is commonly used in fragrances, beauty care, soap, laundry detergents at levels of 0.1 – 1 %. In its very pure form (purity 99.5 %) it is used as a plasticizer in the manufacture of plastics. In the present investigation, kinetics of esterification of pentanoic acid with methanol catalyzed by heterogeneous catalyst in a batch-type reactor is reported. The effect of reaction conditions such as temperature, molar ratio, catalyst loading, and initial concentration of pentanoic acid and methanol, and the inhibiting effect of water on the kinetics has been studied. The pentanoic acid conversion reached 93 % at 333.15 K at a methanol to pentanoic acid molar ratio of 10:1 with 7 % (g L–1) Amberlyst 15 as catalyst. Mass transfer effects were found to be negligible. Observed reaction rate data was fitted to the regression technique. Estimated Eley-Rideal kinetic model reaction rate constants were fitted to the Arrhenius type equation with activation energy EA 39.5 kJ mol–1 and pre exponential factor ko 1.8 · 103 L2 g–1 mol–1 h–1

Interfacial Tension of Some Newtonian and non-Newtonian Fluids by the Drop-Weight Method

Experimental data on interfacial tension of 42 binary liquid-liquid systems using water, aqueous glycerol, aqueous polymeric solutions of polyvinylpyrrolidone (PVP), poly(ethylene oxide) (PEO), carboxymethyl cellulose (CMC) and polyacrylamide (PAM) as continuous phase, and carbon tetrachloride, chlorobenzene, bromobenzene, nitrobenzene, nitrotoluene and ethyl chloroacetate as dispersed phase at 20 °C are reported. The interfacial tension has been measured using the drop-weight method at different compositions of continuous phases

Structural Parameters and Swelling Behavior of pH Sensitive Poly(acrylamide-co-acrylic acid) Hydrogels

In the present work, hydrogels based on acrylamide (AAm) and acrylic acid (AAc), crosslinked with N,N’-methylenebisacrylamide (MBAAm) were prepared by free radical polymerization in solution. The effect of initial AAm/AAc mole ratio and nominal crosslinking ratio (moles of crosslinking agent/moles of polymer repeat unit) on the dynamic and equilibrium swelling behaviour of hydrogels was investigated. Hydrogels were characterized by the polymer volume fraction in the swollen state (ν2,s ), the number average molecular mass between crosslinks (Mc ) and the mesh size (ξ). The swelling capacity of hydrogels was found to decrease with increasing nominal crosslinking ratio. The results show a significant influence of AAc monomer concentration on swelling behavior of poly(acrylamide-co-acrylic acid) hydrogels. Hydrogels containing higher acrylic acid content had a higher equilibrium mass swelling at pH 7.4 and in distilled water than at pH 3.0 where the acrylic acid is present in nonionized state. Further, swelling data was fitted to various models and model parameters were evaluated using regression technique. Model analysis indicated that the swelling transport followed non-Fickian mechanism. Scanning electron microscopy (SEM) revealed the macroporous surface morphology of the matrix with pore size varying between 2–64 microns depending on the amounts of AAc in the hydrogel

Hydrogels of Poly(acrylamide-co-acrylic acid): In-vitro Study on Release of Gentamicin Sulfate

Poly(acrylamide-co-acrylic acid) hydrogels, poly(AAm-co-AAc), were synthesized by free radical polymerization in solution using N,N’-methylenebisacrylamide (MBAAm) as the crosslinker. The structural parameters and the swelling behavior of the synthesized hydrogels were investigated for varying nominal crosslinking ratio and composition of the hydrogels. The use of hydrogels for drug release was investigated with gentamicin sulfate (GS) as the model drug. The drug release from hydrogels was investigated as a function of hydrogel composition, nominal crosslinking ratio (X) and drug loading. The observed drug release data was fitted to a power law model and the power law exponent (n) suggested that the drug release mechanism from these hydrogels was sensitive to hydrogel composition and was swelling-controlled for low concentrations of AAc and showed Fickian diffusion for high concentrations of AAc in the hydrogels. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies were performed on control hydrogel samples and drug loaded hydrogels to understand the chemical interactions between the drug and the polymer. Specific drug interactions were observed in these hydrogels

Sorption and Drug Release Studies from Semi-interpenetrating Polymer Networks of Chitosan and Xanthan Gum

Hydrogel films of Chitosan (CS) and Xanthan gum (XA) of compositions 100/0, 90/10, 80/20, 70/30, 60/40 and 50/50 (w/w) % were prepared and swollen in simulated gastric fluid (SGF) of pH 1.2 and simulated intestinal fluid (SIF) of pH 7.4. To impart stability in acidic environment, semi-interpenetrating polymer network (semi-IPNs) films were formed using glutaraldehyde (GA) as the crosslinking agent. With increase in XA concentration, equilibrium degree of swelling reduced in SGF as well as SIF indicating maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The swelling data was observed to follow second order kinetics. Spectroscopic and thermal analyses of these semi-IPN films also suggest maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The potential of using 50/50 semi-IPN in drug delivery was studied using amoxicillin. In-vitro drug release studies indicated higher drug release in SGF than in SIF suggesting dependence of amoxicillin release kinetics and diffusion coefficient on pH of the environment and drug loading. The results suggest that CS-based semi-IPNs with different crosslinker and XA concentration could be promising candidates for formulation in oral gastrointestinal delivery systems