Animesh Kumar Rakshit

Castor oil based polyurethane adhesives for wood-to-wood bonding

Most adhesives are polymeric adhesives and if made from renewable sources they will have low cost and biodegradability which are of importance. In view of these properties we synthesized polyurethane (PU) adhesives from three different polyester polyols, obtained by reacting a castor oil derivative and diols (glycols) with diisocyanate adducts, where different NCO/OH ratios were used to give various compositions. The polyols and PUs were characterized by FTIR spectroscopy. The effect of NCO/OH ratios, types of isocyanate adducts and chain length of glycols were studied, by determining wood-to-wood adhesion strength, i.e. by lap shear strength measurement. The change in lap shear strength after being placed in cold water, hot water, acid or alkali solutions was tested. Thermal stability of these PU adhesives was determined by thermogravimetric analysis.

The effects of various foreign substances on the cloud point of Triton X 100 and Triton X 114

The nonionic surfactants Triton X 100 and Triton X 114 form isotropic micellar solutions around 25°C. One of the characteristic features of these solutions is the fact that at higher temperatures they undergo clouding and liquid-liquid phase separation. Addition of various additives to the surfactant solutions does change the temperature at which the clouding phenomenon occurs. In this paper such effect of additives on the clouding phenomenon of Triton X 100 and Triton X 114 are discussed.

Study of the cloud point of C12En nonionic surfactants: effect of additives

Abstract Nonionic surfactants are useful in the formation of emulsions. The aqueous solutions of these surfactants show complex phase behaviour including liquid–liquid phase separation at higher temperature. Addition of foreign substance to surfactant solutions does change the temperature at which the clouding phenomena occurs. In this article, we report the effect of electrolytes as well as nonelectrolytes on the cloud point (CP) of a series of nonionic surfactants of the poly(oxyethylene)ether type C12En (n=6, 9, 10). It was observed that NaI and KI have different effect on the CP from that of NaCl, NaBr, KCl and KBr. Tetra butyl ammonium iodide (TBAI) acts differently on the CP from the Tetra methyl ammonium bromide (TMAB). Overall the electrolytes and nonelectrolytes have a large amount of effect on CP of nonionic surfactants, because of their effect on water structure and their hydrophilicity.

Thermodynamics of micellization of a nonionic surfactant: Brij 35 in aquo-sucrose solution

Abstract The critical micelle concentration (CMC) of the nonionic surfactant, Brij 35, was determined by the iodine solubilization method at four different temperatures, 35, 40, 45, and 50°C, in a series of aquo-sucrose solutions, to study the effect of sucrose on the micellization process. The free energy, enthalpy, and entropy of micellization have been computed and are related with the possible structure of the solvent system. An enthalpy—entropy compensation effect is observed in all solvent systems and the computed slope of the line is related with the micellization process. The thermodynamic quantities for the transfer of the micelle from water to different solvents have also been computed and discussed.

Thermodynamics of micellization of a non-ionic surfactant Myrj 45 : effect of additives

Abstract Critical micelle concentrations of the non-ionic surfactant Myrj 45 in aqueous solution at various temperatures (35, 40, 45 and 50°C) were determined by the iodine solubilization method. A few systems were also studied by direct surface tension measurement. The effect of additives, e.g. PEG 400, sucrose, acetamide and urea, on the CMC was studied. The free, energy enthalpy and entropy of micellization were determined. A negative free energy and a positive entropy of micellization were observed for all the systems. The micellization process was exothermic in all cases except in aqueous solution without additives, where the process was endothermic. An enthalpy-entropy compensation effect was observed for all the systems. Transfer enthalpies and heat capacities were evaluated from enthalpy of micellization data. The transfer enthalpy Δ Hm,tr was negative throughout, indicating the transfer of hydrophilic groups from water to the aqueous additive solutions. A maximum observed in the plot of ΔCp,m,tr-concentration of additives was ascribed to a micellar structural transition.

Enthalpy-Entropy Compensation (EEC) Effect: A Revisit.

A short account of the developments and perspectives of IKR (iso-kinetic relation) and EEC (enthalpy (H) - entropy (S) compensation) has been presented. The IKR and EEC are known to be extra thermodynamic or empirical correlations though linear H-S correlation can be thermodynamically deduced. Attempt has also been made to explain the phenomena in terms of statistical thermodynamics. In this study, we have briefly revisited the fundamentals of both IKR and EEC from kinetic and thermodynamic grounds. A detailed revisit of the EEC phenomenon on varied kinetic and equilibrium processes has been also presented. Possible correlations among the free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) changes of different similar and nonsimilar chemical processes under varied conditions have been discussed with possible future projections.

Terpolymerization of acrylamide, acrylic acid, and acrylonitrile : Synthesis and properties

Free-radical solution terpolymerization of acrylamide, acrylic acid, and acrylonitrile was carried out in a mixture of dimethylformamide and water (60 : 40,v/v) at 85°C using benzoyl peroxide as the initiator. The polymers were characterized by elemental analysis, IR, 1H-NMR, TGA, and viscosity measurements. Elemental analysis data were used to evaluate the terpolymer composition. The reactivity ratios were determined by Fineman–Ross and Kelen–Tudos methods. The reactivity ratios (r) for the copolymerization of (1) acrylic acid + acrylonitrile with (2) acrylamide was found to be r1 = 0.86 ± 0.09 and r2 = 1.93 ± 0.03, respectively, by the Kelen–Tudos method. The Fineman–Ross method yielded a value of r1 = 0.86 ± 0.05 and r2 = 1.94 ± 0.09, respectively. The activation energy values for various stages of decomposition were calculated from TGA analysis. Voluminosity (VE) and the shape factor (ν) were also computed from the viscosity measurements in different ratios of the solvent mixture.

Synthesis and characterization of some water soluble polymers

Homopolymers and copolymers of acrylamide (AA) and acrylic acid (AAc) were synthesized by the free radical solution polymerization technique. Feed ratios of the monomers were 85 : 15 (w/w), 65 : 35 (w/w), and 50 : 50 (w/w) of acrylamide and acrylic acid, respectively, for synthesis of copolymers. All reactions were carried out in aqueous media, except for the synthesis of polyacrylic acid, where the medium was n-butanol. Hydrogen peroxide, potassium persulfate, and benzoyl peroxide were used as initiators. The copolymers were purified by removing homopolymers. The homopolymers and copolymers were characterized by infrared (IR), 13C-nuclear magnetic resonance (NMR), 1H-NMR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and viscosity measurements. The fusion temperature and the energy change for various phase transitions were obtained from DSC measurements. The activation energy values for various stages of decomposition were calculated from TGA. The activation parameters for the viscous flow (i.e., free energy, enthalpy, and entropy of activation) were evaluated from the viscosity measurements. Voluminosity and Simha shape factor were also calculated for different systems. Effects of various concentrations of electrolytes, NaNO3, and Al(NO3)3 on viscosity behavior were studied.

Effects of mixed alkanols as cosurfactants on single phase microemulsion properties

Abstract The phase behaviour and properties of a microemulsion system cyclohexane-SDS+alkanolwater, where alkanol indicates various mixtures of two short chain alcohols, were studied. The alcohols used as cosurfactants were propanol and hexanol. The surfactant to cosurfactant weight ratio was kept at 1:2. The phase behaviour study includes determination of the phase diagram and Winsor transitions while the properties studied were conductance, viscosity and adiabatic compressibility. The area of the single phase microemulsion region in the ternary phase diagram increased considerably in systems containing mixed alkanols as cosurfactants, compared with pure alkanol containing systems. The nature of Winsor transitions also changed drastically when an alkanol mixture was used. Temperature increase induces a Winsor transition in the order II→III→I in the mixed systems which was opposite to the trend observed in the pure propanol containing system. The conductivity studies in the mixed alkanol systems revealed that the mixtures of two alkanols behave somewhat like alcohols of carbon chain lengths (C 4 or C 5 ) intermediate between those of the two components. The viscosity and adiabatic compressibility studies highlighted the nonideal behaviour of mixing.

Interfacial, Thermodynamic, and Performance Properties of α‐Sulfonato Myristic Acid Methyl Ester—Hexaoxyethylene Monododecyl Ether Mixed Surfactants

Abstract The interfacial, thermodynamic, and performance properties of the aqueous α‐sulfonato myristic acid methyl ester (MES)—hexaoxyethylene monododecyl ether (C12E6) mixed surfactant system have been investigated. The critical micelle concentrations (cmcs) were obtained by surface tension and conductivity measurements. The maximum surface excess (Γmax) and minimum area per molecule (A min) were determined from surface tension (γ)–log concentration (log C) plots. The thermodynamic parameters of micellization and adsorption were computed. Micellar aggregation numbers (N agg) of pure and mixed surfactant systems were evaluated by fluorescence measurements. Interaction parameters between surfactant molecules in mixed micelles were evaluated using Rubinghs approach. The performance properties of pure and mixed surfactant systems viz. foaming, detergency, and viscosity were studied. Cloud point (CP) determinations of the nonionic C12E6 in the presence of electrolytes (NaCl, NaBr, and NaI) and nonelectrolytes like polyethylene glycols (MW 200, 300, and 400) were also carried out.