Influence of physical properties and operating parameters on hydrodynamics in Centrifugal Partition Chromatography

Besides the selection of a suitable biphasic solvent system the separation efficiency in Centrifugal Partition Chromatography (CPC) is mainly influenced by the hydrodynamics in the chambers. The flow pattern, the stationary phase retention and the interfacial area for mass transfer strongly depend on physical properties of the solvent system and operating parameters. In order to measure these parameters we visualized the hydrodynamics in a FCPC-chamber for five different solvent systems with an optical measurement system and calculated the stationary phase retention, interfacial area and the distribution of mobile phase thickness in the chamber. Although inclined chambers were used we found that the Coriolis force always deflected the mobile phase towards the chamber wall reducing the interfacial area. This effect increased for systems with low density difference. We also have shown that the stability of phase systems (stationary phase retention) and its tendency to disperse increased for smaller values of the ratio of interfacial tension and density difference. But also the viscosity ratio and the flow pattern itself had a significant effect on retention and dispersion of the mobile phase. As a result operating parameters should be chosen carefully with respect to physical properties for a CPC system. In order to reduce the effect of the Coriolis force CPC devices with greater rotor radius are desirable.     

Studies on the properties and characteristics of starch-LDPE blend films using cross-linked, glycerol modified, cross-linked and glycerol modified starch

Corn starch was modified by cross-linking with epichlorohydrin and plasticizer glycerol. X-ray diffraction studies showed that relative crystallinity of the native and cross-linked starch were similar and were not affected by cross-linking. Different films were prepared by blending corn starch, cross-linked starch or glycerol modified starch in LDPE. The mechanical properties of the films were studied for tensile strength, elongation, melt flow index, and burst strength. The properties of the blend films were compared with LDPE films. It was observed that with the blending of 7.5% native starch, there was a decrease in tensile strength, elongation and melt flow index but burst strength increased. The tensile strength, elongation and melt flow index of the films containing cross-linked starch was considerably higher than those containing native starch but the burst strength showed a reverse trend. For native starch and cross-linked starch modified with glycerol, the elongation and melt flow index of the films increased but burst strength decreased. Surface scanning of the blend films were done by scanning electron microscope. Film containing cross-linked starch/glycerol modified starch in the blend was observed to be smoother than the native starch blend films.     

Influence of conformational parameters on physical properties of copolyimides containing pendant diphenylphosphine oxide units

Modification or designing new molecular architectures are the key strategies to obtain materials with improved/tunable properties able to address environmental restrictions and public needs. Herein, a series of copolyimides containing bulky diphenylphosphine oxide pendant units was synthesized and the physical properties were studied and correlated with the conformational parameters, such as Kuhn segments, Van der Waals and free volumes. It is shown that conformational rigidity determines the packing of macromolecules in glass state, and therefore the free volume, glass transition and dielectric permittivity. The Kuhn segment of the synthesized random copolyimides calculated by Monte Carlo method exhibited a nonlinear dependence on chemical composition. The use of correlations between the chemical structure and conformational parameters is the key to achieve polymers with tailored physicochemical characteristics by varying the comonomers’ ratio.     

Thermal properties and stability of cassava starch films cross-linked with tetraethylene glycol diacrylate

The thermal stability of starch cross-linked with tetraethylene glycol diacrylate was studied under nitrogen atmosphere by thermogravimetry (TG) and infrared spectroscopy (FTIR). The cross-linking reaction was confirmed by the increase in intensity of the absorption band at ca. 3330 cm⁻¹ indicating the reinforcement of hydrogen bonds and the appearance of a new band at 1726 cm⁻¹ associated with the carbonyl group of the cross-linking agent. After cross-linking the solubility of starch in water decreased to the range 9%-16%. The thermogravimetric curves of pure and cross-linked starches showed an initial stage of degradation (up to ca. 150 °C) associated with the loss of water. The main stage of degradation occurred in the range 250-400 °C corresponding to ca. 60%-70% mass loss. The activation energy (E) for the degradation process increased from 145 kJ mol⁻¹ (pure starch) to 195 kJ mol⁻¹ and 198 kJ mol⁻¹ for starch treated for 60 min by UV (30 °C) and at 90 °C, suggesting high stability after cross-linking. A higher value (240 kJ mol⁻¹) was obtained for starch treated by UV for 120 min. The main volatile products determined by FTIR which correspond to hydrocarbons and carbonyl groups are apparently associated with the scission of weak bonds in the chain (probably branched groups) and the scission of stronger bonds (glycosidic linkages), respectively.     

Influence of carbon black on thermal properties and flammability of cross-linked elastomers

The paper presents the results of testing thermal properties and combustibility of butadiene-acrylonitrile rubber vulcanizates with different contents of bounded acrylonitrile: Perbunan NT 1845 and Perbunan NT 3945 from Bayer. The rubbers were cross-linked by means of dicumyl peroxide. Four types of carbon black with different specific surfaces were used as fillers. The test results were obtained with the use the derivatograph, DSC-204 of Netzsch, measurements of flammability by the method of oxygen index and in air. The results of measurements have shown that the thermal stability and flammability of the vulcanizates under investigation are affected by the activity of solid phase and the degree of surface development as well as the flexibility of polymeric chain and the degree of its unsaturation. A clear relationship has been found between the thermal properties and flammability of the cross-linked butadiene-acrylonitrile rubbers.     

Influence of cryogenic modification of silica on thermal properties and flammability of cross-linked nitrile rubber

The article presents the results of testing thermal properties and combustibility of butadieneacrylonitrile rubber with 18% contents of bounded acrylonitrile, NBR 18. Two types of silica, Zeosil 175C and Ultrasil VN-3, with different specific surfaces were used as filler. Zeosil 175C and Ultrasil VN-3 were modified via cryogenic dezaggregation method. The activity of unmodified and cryogenic modified silica toward butadiene-acrylonitrile rubber were investigated. The sulphur and peroxide vulcanizates contained 20, 30, 40, and 50 phr. of the filler were studied. The article discusses also the test results of thermal stability and flammability of NBR 18 containing silica prepared "in situ" from alkoxysilane precursor. The test results were obtained with the use of derivatograph, measurements of flammability by the method of oxygen index, and in air. The effect of the silica modification on the SEM and AFM was also examined. The method of cryogenic modification enables to achieve increase of mineral fillers activity towards elastomer and reduction in the flammability of NBR 18 vulcanizates. It has been found that the modification of the vulcanizates of NBR 18 with tetraethoxysilane that makes it possible to form silica "in situ" reduces the flammability of cross-linked rubbers.     

Rapid analysis of starch, amylose and amylopectin by high-performance size-exclusion chromatography

Starch components, amylose and amylopectin, were analyzed by high-performance size-exclusion chromatography. These two-components were separated using a two-column system (E-Linear and E-1000) and dimethyl sulphoxide as the mobile phase. The void volume (V0 = 2.22 ml) was measured using tobacco mosaic virus. Column calibration was accomplished with dextrans of known average molecular weight (Mw range = 10,100-2,000,000). The elution volume of amylopectin (Ve = 2.5 ml) indicated that this starch component was fractionated on the column system despite its very large molecular size. Standard curves were prepared from various mixtures of purified corn and wheat amylose and amylopectin. From the linear relationships obtained, the percentages of both components in corn and wheat starches were determined. The method developed proved useful to monitor the purity of amylose and amylopectin preparations, and to estimate rapidly the amylose:amylopectin ratio of starch samples.     

Fast separation of macrophages by retention on cross-linked amylose and release by enzymatic amylolysis of the chromatographic material.

Macrophages from mice peritoneal exudate were isolated on basis of specific adherence on epichlorohydrin cross-linked amylose (CLA), a chromatographic gel presenting a high susceptibility to advanced amylolysis with alpha-amylase. The cell suspension, containing predominantly macrophages and lymphocytes, was applied onto the column and incubated for 30 min at 37 degrees C for the adherence of macrophages. After this interval the non-adherent cells were eluted with buffered medium and the CLA support was incubated in the column with an alpha-amylase-buffered solution liquefying the matrix and releasing, in situ, the adherent cell population containing 90% macrophages with a viability higher than 90%.     

Synthesis and properties of thermoplastic propyl-etherified amylose

Amylose was etherified with 1-bromopropane in DMSO. The degree of substitution (DS) was varied by altering the feed ratio of 1-bromopropane. The structures of the products were characterized by IR and 1H-NMR spectroscopy. When the molar feed ratio of 1-bromopropane to hydroxyl groups of amylose was beyond 7.5, the hydroxyl groups were completely substituted with propyl ether groups. The etherified amylose with DS 1.9 showed a glass transition temperature (T_g), and that with DS 2.3 or 3.0 showed both T_g and melting temperature (T_m) (DS 3.0 means complete substitution). The etherification imparted melt processability and solubility in nonpolar organic solvent to amylose.     

Role of micro-crystalline parameters in the physical properties of cotton fibers

Karnataka state in India is very well known for its cotton cultivation and there are innumerable varieties of these cotton fibers. Although, the yield and other types of characterization have been carried out on these fibers, the structure-property relation is not well studied till today. We have examined four different raw cotton fibers using Wide Angle X-ray Scattering (WAXS) technique and also we have computed micro-crystalline parameters. This study brings out the structure-property relation in cotton fibers.     

Electrochemical properties of fibrous and granulated carbon materials

The influence exerted by the porous structure of fibrous and granulated carbon materials on the nature of the charging process and depth of penetration of the electrochemical process was studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1811–1814.Original Russian Text Copyright © 2004 by Artemyanov, Sheveleva.     

Influence of metal-containing lubricants on characteristics of polyvinyl chloride

The influence of metal-containing lubricants based on monoesters of glycerol and higher isomeric saturated monocarboxylic acids on characteristics of polyvinyl chloride was studied.     

Effects of starch types on the properties of baked starch foams

In order to determine how the physicochemical properties of starch foams depend on the type of the starch used in baking process, starch foams were prepared using native starch and selected starch derivatives. The morphology, the density, the water adsorption capacity, the impact strength, and the thermal properties were determined for foams made from native starch, pregelatinized starch, hydroxypropylated starch with different degrees of substitution (DS = 0.015–0.025 and DS = 0.1), low distarch phosphate, medium distarch phosphate, and two cationic starch types (DS = 0.027–0.029 and DS = 0.029–0.033). The modified starch foams exhibited a more expanded structure with thinner cell walls than the foam made from native starch. The density of the native starch was 0.21 g cm^?3 , while the density of the modified starch foams was lower, in the range of 0.14–0.17 g cm^?3 except for the starch foam made from medium distarch phosphate. The thermal and physicochemical properties of the foams made from the other starch derivatives were dependent on the functional groups and the degree of cross-linking. The foam made from medium distarch phosphate had a significantly higher density and impact strength that was accompanied by a somewhat lower water adsorptivity.     

Influence of additives on some physical properties of high density polyethylene-II. commercial u.v. stabilizers

The changes in mechanical properties of processed high density polyethylene, when “u.v. stabilizers” are added, are examined using tensile and melt flow measurements. The results show that, at low additive concentrations, antioxidant effects predominate; at high concentrations, a reinforcement effect is observed. Degradation measurements show that the u.v. stabilizers behave as excellent oxidation inhibitors in the dark; this finding has implications regarding their mechanistic action.     

Influence of crosslinking on physical properties of low density polyethylene

Influence of crosslinking on physical properties of low density polyethylene was studied.The results indicated that,at low degrees of crosslinking,the network hardly affects the crystallinity,elastic modulus(E) and yielding stress while it improves the tensile strength and strain at break simultaneously.Tensile strength reaches a maximum of about 24 MPa at 1.5 phr dicumyl peroxide(DCP) then decreases to a constant value of about 18 MPa due to decrease of crystallinity.E reaches its maximum at 0.5 phr DCP corresponding to gel fraction of about 75%without marked change in crystallinity.The crosslinked polyethylene exhibits two yielding processes,and both yielding stresses approximately linearly depend on crystallinity.     

Anisotropy in the physical properties of UNiGa under high pressure

The linear thermal expansion, compressibility and magnetostriction of UNiGa have been measured under high pressure. Huge anisotropic behaviors are observed in these physical quantities. The linear thermal expansion coefficients are α _a ∼ 16·10⁻⁶ K⁻¹ along thea-axis anda _c ∼5·10⁻⁶ K⁻¹ along thec-axis, and the linear compressibilities at room temperature are κ _a ∼ 3.6·10⁻³ GPa⁻¹ and κ _c ∼ 1.7·10⁻³ GPa⁻¹ alonga-axis andc-axes, respectively. UNiGa orders antiferromagnetically belowT _N=39 K and shows a metamagnetic transition at 4.2 K in magnetic fieldB _C=1 T. It is found thatT _N decreases andB _C increases with increasing pressure.     

Influence of synthesis and operating parameters on silicalite-1 membrane properties

The present study deals with the synthesis of nanostructured silicalite-1 membranes on porous α-Al₂O₃ supports by a hydrothermal method. Different parameters including the synthesis conditions (temperature and alkalinity) and operating conditions (temperature and pressure) were investigated. The membranes were characterized by X-ray diffraction and scanning electron microscopy techniques. The optimum synthesis temperature and alkalinity were determined to be 160 °C and pH = 11, respectively. The permeability of CO₂ and CH₄ through the optimized membrane was determined by the pressure drop method. The results revealed that the main effective separation mechanism was adsorption. The permeation of CO₂ and CH₄ declined with increasing temperature, whereas high feed pressures enhanced the single gas flux. The CO₂ and CH₄ permeability values at 30 °C and 2 bar were 1.62 × 10^?7 and 2.07 × 10^?7 mol m^?2 s^?1 Pa^?1, respectively. Furthermore, the response surface methodology analysis confirmed the significance of all the variables and the proposed model. Excellent correlation between the experimental and predicted data (R² = 0.99) was obtained, confirming that response surface methodology is a powerful tool for modeling nanostructured silicalite-1 membrane processes.     

Influence of flame retardant additives on the processing characteristics and physical properties of ABS

Antimony trioxide (Sb₂O₃) is a common additive in flame retardant formulations and a study has been made to determine the effects of adding different grades into ABS polymer either alone or with commercial brominated materials bis(Tribromophenoxy)ethane (BTBPE) or Tetrabromobisphenol A (TBBA). The results consider mechanical, microscopical and flame retardant properties, and the effects of different Sb₂O₃ grades with average particle sizes of 0.1μm, 0.52μm and 1.31μm. The Sb₂O₃ was added at 4wt% loadings and the bromines at 20wt% loadings. Additions of different grades of antimony trioxide showed that standard grades (0.52 and 1.31μm) had a detrimental effect on impact and flexural properties when added at a 4wt% loading. The use of a new sub‐micron particle size product (0.1μm) had little effect on impact properties and only a slight detrimental effect on the flexural modulus and flexural strength when added to the ABS. Additions of either of the two brominated materials also caused a large drop in impact properties when added at 20wt% loadings. The addition of TBBA BA‐59P into ABS caused an increase in both flexural modulus and flexural strength which was contrary to expectations. When formulated with 4wt% 1.31μm Sb₂O₃ these bromine containing compounds suffered a further reduction in impact energies. Using the 0.1μm material improved both impact and flexural properties but impact values were still below those of unfilled ABS. The addition of the 0.1μm grade resulted in improvements in fire resistance as measured by the UL‐94 properties.