The influence of polyoxypropylenetriamine on the properties of epoxy–thiokol mixtures

The influence of Jeffamine T-403 polyoxypropylenetriamine on the physico-mechanical, adhesion, and relaxation properties of polymeric compositions based on the products of preliminary thioesterification reaction of epoxy resin with liquid thiokol was studied. It was shown that the introduction of polyoxypropylenetriamine leads to a significant increase of the adhesive and cohesive strength, the elongation at break, and the work of destruction of the material.     

Effect of glycerol on the optical and physical properties of sol–gel glass matrices

Glass samples are prepared with different amount of glycerol as drying control chemical additive (DCCA) via acid catalysed sol–gel method. These samples are given solvent treatment namely rinse and dip with methanol while drying of the sample. In rinse treatment solid sample is rinsed with small amount of methanol while in dip treatment sample is dipped for 5 h in methanol. Comparative studies of these treated samples containing varied DCCA concentration are carried out by measuring optical transmission, mechanical strength and bulk density. Various instrumental techniques used for analysis are FTIR, DTA-TGA, XRD, SEM and TEM. The untreated samples take long time to dry up and to come out of the cuvette and show very less transmission in UV region which is much enhanced by solvent treatment. On the basis of this study, the solvent treated glass samples with DCCA amount 8 ml in the composition used are found to have the maximum UV transmission, good mechanical strength and may be useful as silica gel host matrices for solid state dye lasers and other applications. The UV transmission reported in the present studies is 90% in 337 nm region, which is the wavelength of N₂ laser pumping.     

The effect of coal particle aggregation on the sedimentation and rheology of coal—oil mixtures

The degree of coal particle aggregation in model oil suspension was assessed by particle size distribution using a sedimentation balance. Various statistical parameters were calculated for three suspensions each prepared with Sewell coal, model oil, and (1) calcium petroleum sulfonate (2) no additive and (3) an ethoxylated quartenary ammonium salt. These formulations represented suspensions which were (1) aggregatively stable (2) slightly aggregated and (3) highly aggregated, respectively.Batch settling tests were also conducted with the three formulations at coal concentrations of 10, 35 and 50%. These results indicated that the clarity of the supernatant, the initial settling velocity and the terminal sediment volume increased as the degree of aggregation increased. Rheological data indicated that the aggregatively stable suspensions were Newtonian but that pseudoplasticity and yield stresses were observed in the other formulations to an extent which increased as the degree of aggregation increased.     

Effect of chemical structure of hydroxyethyl imidazolines inhibitors on the CO2 corrosion in water–oil mixtures

The corrosion inhibition of oleic, coconut, and stearic acid modified hydroxyethyl imidazolines on 1018 carbon steel was evaluated by using potenthiodynamic polarization curves, linear polarization resistance, and electrochemical impedance spectroscopy techniques. Solutions included deaerated CO₂ saturated 3% NaCl with and without Diesel at 50 °C. Regardless of the presence of diesel, the corrosion rate was decreased with the addition of the inhibitors, but the time to reach a steady state was longer than when the oily part, i.e., diesel, was present. This was because the inhibitors are oil soluble, and with diesel, they are more easily transported towards the metal surface. With diesel, the formed film seems to be more stable and protective, not allowing the electrolyte to corrode the sample increasing the efficiency values up to 87 and 94%. The most efficient inhibitors were the coconut type fatty acid hidroxyethyl imidazoline because the formed film was much more stable from the beginning of the test, whereas the least efficient was the stearic acid modified hydroxyethyl imidazoline.     

Effect of alkanolamines on properties of epoxy–anhydride compounds

Hot-cured epoxy compound based on ED-20 resin and isomethyltetrahydrophthalic anhydride was modified with alkanolamines of different structures. The influence exerted by the structure of alkanolamines on the structure and operation characteristics of modified epoxy–anhydride compounds was examined. Introduction of alkanolamines decreases the gel and cure times and enhances the operation properties of cured epoxy–anhydride compounds. The best products were obtained with alkanolamines derived from ethylenediamine. Their introduction into epoxy–anhydride compounds enhances by a factor of 1.5–2 the elasticity, tensile strength at uniform extension, and impact resilience of the cured formulations.     

Influence of temperature on thermodynamic properties of acid–base liquid mixtures

Ultrasonic velocity, u density, ?? and viscosity, ?? of mixtures of N,N-dimethyl acetamide with equimolar mixture of ethanol?+?isopropyl alcohol/isobutyl alcohol/isoamyl alcohol, including those of pure liquids over the entire composition have been measured at T?=?308.15, 313.15, and 318.15?K. Using this data, various thermo-acoustic parameters such as deviations in ultrasonic velocity, ?u, isentropic compressibility, ?k _s , viscosity, ????, excess molar volume, $ V_{\text{m}}^{\text{E}} $ and excess Gibb??s free energy of activation for viscous flow, ??G ^*E have been calculated at different temperatures. The calculated deviation and excess functions have been fitted to the Redlich?CKister type polynomial equation. The influence of temperature on the observed negative and positive values of deviation and excess thermodynamic properties has been explained in terms of molecular interactions present in the investigated acid?Cbase liquid mixtures. The experimental data of ultrasonic velocity have been used to check the applicability of velocity models of Nomoto, Van Dael and Vangeel and Junjie and viscosity data have also been availed to test the applicability of standard viscosity models of Grunberg-Nissan, Hind-Mc Laughlin, and Katti-Chaudhary for all the systems investigated at various temperatures.     

Effect of a magnetic field on the rheological properties of the systems hydroxypropyl cellulose–ethanol and hydroxypropyl cellulose–dimethyl sulfoxide

With the use of viscometry, the cloud-point method, polarization microscopy, the turbidity-spectrum method, and a polarization photoelectric apparatus, the relaxation pattern of the rheological behaviors, phase transitions, and structures of the systems hydroxypropyl cellulose–ethanol and hydroxypropyl cellulose–dimethyl sulfoxide are studied. The regions of existence of isotropic and anisotropic phases and the concentration dependence of the sizes of supramolecular particles are determined. It is found that a magnetic field increases the viscosities of solutions. The concentration dependences of viscosity and particle size are described by curves with maxima.     

Effect of POSS on thermomechanical properties of epoxy–POSS nanocomposites

The epoxy–POSS hybrid networks with POSS bound as pendant cages or with untethered POSS dispersed in the matrix were prepared and their structure was controlled. Formation of the hybrid network was followed by chemorheology. In situ development of physical crosslinks in the pregel stage of the network build-up was observed in case of the hybrids with tethered POSS. The complex effect of POSS on mechanical properties is manifested by either increase or decrease in rubbery modulus of different hybrids. This behavior reflects (a) reinforcement due to POSS hard aggregates, (b) diminishing of crosslinking density of the epoxy network by tethered monofunctional POSS and (c) physical crosslinking via POSS domains. Theories of network formation and rubbery elasticity as well as the model of mechanical behavior of particulate composites were applied to interpret the mechanical properties of the hybrids.     

Effect of pressure on the structure and dynamics of hydrogen bonds in ethylene glycol–water mixtures: Numerical simulation data

Water?ethylene glycol mixtures containing from 0.002 to 0.998 mole fractions of ethylene glycol at T = 298.15 K and P = 0.1 and 100 MPa are simulated by means of classical molecular dynamics. Such structural and dynamic characteristics of hydrogen bonds as the average number and lifetime, along with the distribution of molecules over the number of hydrogen bonds, are calculated; their changes are analyzed, depending on the mixture’s composition and pressure. It is shown that the components are characterized by a high degree of interpenetration and form a uniform infinite hydrogen-bonded cluster over the range of concentrations. It is found that the higher the concentration of ethylene glycol, the greater the stability of all hydrogen bonds. It is concluded that an increase in pressure lowers the number of hydrogen bonds, while the average lifetime of the remaining hydrogen bonds grows.     

Surface tension isotherms of the dioxane–acetone–water and glycerol–ethanol–water ternary systems

The results of the experimental and theoretical studies of the concentration dependence of surface tension of aqueous solutions of the 1,4-dioxane–acetone–water and glycerol–ethanol–water ternary systems were given. The studies were performed by the hanging-drop method on a DSA100 tensiometer. The maximum error of surface tension was 1%. The theoretical models for calculating the surface tension of the ternary systems of organic solutions were analyzed.     

The rheological properties of gelatin gels containing κ-carrageenan. The role of polysaccharide

The influence of an anionic polysaccharide, κ-carrageenan, on the rheological properties of low-concentration (1.0 wt %) gelatin gels has been studied in a wide range of low polysaccharide concentrations (1 × 10^?3–5 × 10^?1 wt %) at a temperature of 14.0°C and pH values slightly higher than the isoelectric point of gelatin. The parameters characterizing the rheological properties of the gels are governed by the mass ratio between the polysaccharide and gelatin, which are able to form (bio)polyelectrolyte complexes in aqueous systems. There is a critical κ-carrageenan-to-gelatin mass ratio Z ? 0.1, above which the yield stress of the gels and their effective viscosit at stresses exceeding the yield point drastically rise. The increase in these rheological parameters correlates with a growth in the particle size of κ-carrageenan-gelatin polyelectrolyte complexes, which are formed in the aqueous bulk phase at an elevated temperature and precede gelation.     

Effect of reaction conditions on surface properties of TEOS–TBOT–PDMS hybrid materials

Hybrid materials based on tetraethoxysilane (TEOS), tetrabutyl orthotitanate (TBOT), and hydroxyl terminated polydimethyl siloxane (PDMS) have been prepared and characterized. The effects of HCl concentration and PDMS molecular weight (M_W) have been analysed. The physical and chemical characteristics have been discussed based on the results obtained from the characterization by Raman spectroscopy, nitrogen adsorption, mercury intrusion porosimetry and inverse gas chromatography (IGC). Specific surface areas (SSA) and pore volumes increase with HCl concentration and are independent on the PDMS Mw. SSA values as high as 300 m² g⁻¹ have been obtained for hybrid materials prepared with HCl:(TEOS + TBOT) concentration of 0.3 and PDMS Mw of 550 g mol⁻¹. These materials present the higher pore volumes and lower pore sizes. However, for HCl:(TEOS + TBOT) concentration of 0.5, only macroporous materials are obtained with SSA values as low as 2–4 m² g⁻¹, and pore sizes close to 10 μm. In general the presence of Ti on the SSA and porosities give a little decrease in such values. Surface energies are consistent with those of organic–inorganic materials. Dispersive surface energies are higher for the Si–Ti hybrid materials and, for all of them, they decrease with both HCl concentration and PDMS Mw. This result can be assigned to the presence of a higher concentration of PDMS (or CH₃ groups) on the surface of the hybrid material as well as the presence of disordered anatase-like structures. On the other hand, the acid and base properties are dependent on both HCl concentration and PDMS Mw. It has been observed that the acid and base parameters of the Si–Ti hybrid materials are influenced by the disorder degree of the amorphous titanium oxide present in them. As the disorder decrease both acid and base parameters increase.     

Effect of epoxidation of natural rubber on the pervaporation separation of acetone–chlorinated hydrocarbon mixtures

The pervaporation separation and the swelling behavior of chlorinated hydrocarbon/acetone mixtures were investigated using natural rubber (NR) and epoxidized natural rubber (ENR) membrane with 25 and 50 mol% epoxidation, respectively. The swelling degree increases with increase in the epoxidation level. The flux and separation factor of the membranes were determined both as a function of mole percent epoxidation and of the feed mixture composition. The membranes were found to be permselective to chlorinated hydrocarbons from acetone–chlorinated hydrocarbon mixtures. The flux decreases with increase in epoxidation level, whereas the separation factor increases. The permeation decreases and separation factor increases with increase in the acetone feed concentration. The availability of raw materials, low cost of implementation and easy processability of the system makes this method of separation highly applicable and recommendable.     

Effect of molybdenum addition on the thermal properties of silicate–phosphate glasses

Aim of the study was analysis of two groups of glasses: silicate?Cphosphate (41?mol.% SiO₂?C6?mol.% P₂O₅) and with inverse phosphate?Csilicate matrix (41?mol.% P₂O₅?C6?mol.% SiO₂) modified by the addition of molybdenum ions. Their effect on glass forming ability, glass transition effect, crystallization process, and kind of crystallizing phases was examined using such methods as DSC, XRD, and SEM. It was found that the solubility limit of MoO₃ in silicate?Cphosphate glasses is 4.4?<?[MoO₃]?<?5.7?mol.%, whereas in phosphate?Csilicate glasses MoO₃ is fully dissolved. It was found that in the case of both matrixes addition of molybdenum ions decreases the glass transition temperature (T _g), as well as the value of specific heat change (?c _p ) accompanying the glass transformation. The presence of molybdenum caused reduced the thermal stability of the studied glasses and a multi-step crystallization of silicate?Cphosphate glasses. It was found that the crystallizing phases were silicates and phosphates in both groups of glasses. Only in the case of silicate?Cphosphate glasses containing MoO₃ in an amount ??3.3?mol.% one of the crystallization product was powellite (CaMoO₄). The nature of transitions taking place during heating of the analyzed glasses was in accordance with crystallochemical factors (strengths of bonds) and chemical affinity of the glass components (?G formation).     

Effect of tri-n-butyl phosphate on physical properties of dodecane–nitric acid system

Extraction power of solvent depends upon the physical properties of the system. Tri-n-butyl phosphate (TBP) in dodecane is a versatile solvent used in the nuclear fuel reprocessing like PUREX process. The study of physical properties like density, viscosity, interfacial tension and solubility for TBP–nitric acid–dodecane system will be helpful in carrying out different extraction studies during PUREX process. Thus, physical properties like density, viscosity, interfacial tension and solubility have been measured for TBP–nitric acid–dodecane system using pycnometer, viscometer, pendant drop method and high performance liquid chromatography respectively. It has been observed that density and viscosity increases but interfacial tension and solubility decreases with the concentration of TBP in dodecane–nitric acid system. Physical properties of 30 % TBP–nitric acid–dodecane system have also been studied in detail. All these studies will also be useful in stripping out dissolved TBP from the nuclear waste.     

Sol–gel transition and rheological properties of silica nanoparticle dispersions

Possible variants of the rheological behavior of silica model dispersions have been analyzed. Different types of interaction between the particles and a dispersion medium make it possible to obtain different systems from low-viscosity sols to gels. Proton-donor (water) and aprotic (dimethyl sulfoxide) media have been used for comparison. Dispersions in the aprotic medium behave as non-Newtonian viscous fluids exhibiting shear thinning or shear thickening depending on deformation rate. Aqueous dispersions are viscoelastic and viscoplastic objects that exhibit the shear thickening at stresses higher than the yield stress. The introduction of small amounts of poly(ethylene oxide) into the organic dispersion medium initiates gelation. An increase in the polymer content in the dispersion medium above the concentration corresponding to the formation of a macromolecular network promotes an increase in stiffness and strength of the gels. The rheological behavior of gels is influenced by the polymer molecular mass and its affinity for a solvent.