Decrease In Relative Viscosity Research Articles

Extensional rheology of a dilute particle-laden viscoelastic solution

Numerical simulations of viscoelastic flow around an isolated particle find that, while the particle contribution to bulk elongational viscosity of a suspension increases at small strains, at larger strains the particle is shielded by stretched polymers, leading to a decrease in relative viscosity.

Optimization and development of stable w/o/w cosmetic multiple emulsions by means of the Quality by Design approach.

The aim of our present work was to develop stable water-in-oil-in-water (w/o/w) cosmetic multiple emulsions that are proper for cosmetic use and can also be applied on the skin as pharmaceutical vehicles by means of Quality by Design (QbD) concept. This product design concept consists of a risk assessment step and also the 'predetermination' of the critical material attributes and process parameters of a stable multiple emulsion system. We have set up the hypothesis that the stability of multiple emulsions can be improved by the development based on such systematic planning - making a map of critical product parameters - so their industrial usage can be increased. The risk assessment and the determination of critical physical-chemical stability parameters of w/o/w multiple emulsions to define critical control points were performed by means of quality tools and the leanqbd(™) (QbD Works LLC, Fremont, CA, U.S.A.) software. Critical materials and process parameters: Based on the results of preformulation experiments, three factors, namely entrapped active agent, preparation methodology and shear rate, were found to be highly critical factors for critical quality attributes (CQAs) and for stability, whereas the nature of oil was found a medium level risk factor. The results of the risk assessment are the following: (i) droplet structure and size distribution should be evaluated together to be able to predict the stability issues, (ii) the presence of entrapped active agents had a great impact on droplet structure, (iii) the viscosity curves represent the structural changes during storage, if the decrease in relative viscosity is >15% the emulsion disintegrates, and (iv) it is enough to use the shear rate between 34g and 116g relative centrifugal force (RCF). CQAs: By risk assessment, we discovered that four factors should be considered to be high-risk variables as compared to others: droplet size, droplet structure, viscosity and multiple character were found to be highly critical attributes. The preformulation experiment is the part of a development plan. On the basis of these results, the control strategy can be defined and a stable multiple emulsion can be ensured that meets the relevant stakeholders' quality expectations.

Biodeterioration of cinematographic cellulose triacetate by Sphingomonas paucimobilis using indirect impedance and chemiluminescence techniques

The bacterium Sphingomonas paucimobilis, isolated from cinematographic films in an earlier project, was able to biodeteriorate the cellulose triacetate material (acetylation degree of 2.7). Film colonization was monitored by the indirect impedance technique and the production of carbon dioxide. The presence of ruggedness and irregularities on the surface of the film, produced when the plasticizer was extracted, accelerated the biodeterioration of the material. In contrast, cinematographic films with their layered structure made of photographic gelatine emulsion were protected and no colonization was observed. The cinematographic film without photographic emulsion reached a 5% level of biodeterioration after six weeks of incubation, confirming the possibility of biodeterioration of archival cinematographic materials if conservation conditions are not adequate. Through viscosity measurements, a decrease in relative viscosity was observed on the biodeteriorated sample, with respect to the original material, confirming a lower molecular weight as a result of enzymatic activity of S. paucimobilis. Also, using chemiluminescence, the film surface oxidation on the biodeteriorated sample was observed. This technique was very sensitive in detecting material oxidation by reactive oxygen species generated by bacteria, and could be useful to study microbiological biodeterioration in polymeric materials.

Copper(II) complexes of tridentate pyridylmethylethylenediamines: Role of ligand steric hindrance on DNA binding and cleavage

Copper(II) complexes of three linear unsymmetrical tridentate ligands viz. N-methyl- N′-(pyrid-2-ylmethyl)ethylenediamine (L1), N, N-dimethyl- N′-(pyrid-2-ylmethyl)ethylenediamine (L2) and N, N-dimethyl- N′-((6-methyl)pyrid-2-ylmethyl)ethylenediamine (L3) have been isolated and characterized by elemental analysis, electronic absorption and EPR spectroscopy and cyclic and differential pulse voltammetry. Of these complexes [Cu(L2)Cl 2] and [Cu(L3)Cl 2] have been structurally characterized by X-ray crystallography. The [Cu(L2)Cl 2] complex crystallizes in the monoclinic space group P2 1/ n with a = 11.566(2) Å, b = 7.369(1) Å, c = 15.703(3) Å, α = 90°, β = 109.68(8)°, γ = 90° and Z = 4 while [Cu(L3)Cl 2] crystallizes in the triclinic space group P 1 ¯ with a = 9.191(2) Å, b = 12.359(3) Å, c = 14.880(3) Å, α = 79.61(13)°, β = 86.64(13)°, γ = 87.28(8)° and Z = 2. The coordination geometries around copper (II) in these two complexes are best described as trigonal bipyramidal distorted square based pyramidal (TBDSBP). The distorted CuN 3Cl basal plane in them is comprised of three nitrogen atoms of the meridionally coordinated ligand and a chloride ion and the axial position is occupied by the other chloride ion. The interaction of these complexes with Calf Thymus DNA (CT DNA) has been studied by using absorption, emission and circular dichroic spectral methods, thermal denaturation studies, viscometry and cyclic and differential pulse voltammetry. A strong blueshift in the ligand field band and a redshift in the ligand based bands of the copper(II) complexes on binding to DNA imply a covalent mode of DNA binding of the complexes, which involves coordination of most possibly guanine N7 nitrogen of DNA to form a CuN 4 chromophore. This is supported by studying the interaction of the complexes with N-methylimidazole ( N-meim), guanosine monophosphate (GMP), adenosine monophosphate (AMP) and cytidine (cytd) by ligand field and EPR spectral methods, which indicate the formation of a CuN 4 chromophore only in the case of the more basic N-meim and GMP. The DNA melting curves obtained in the presence of copper(II) complexes reveal a monophasic and irreversible melting of the DNA strands and the high positive Δ T m values (12–21 °C) also support the formation of strong Cu–N bonds by the complexes with DNA, leading to intra- and/or interstrand crosslinking of DNA. Competitive ethidium bromide (EthBr) binding studies show that the L2 and L3 complexes are less efficient than the L1 complex in quenching EthBr emission, which is consistent with their forming DNA crosslinking preventing the displacement of the DNA-bound EthBr. A very slight decrease in relative viscosity of DNA is observed on treating the L1 and L2 complexes with CT DNA; however, a relatively significant decrease is observed for the L3 complex suggesting that the length of the DNA fiber is shortened. DNA cleavage experiments show that all the complexes induce the cleavage of pBR322 plasmid DNA, the complex of L1 being more efficient than those of sterically hindered L2 and L3 ligands.

Study of albedo and carpelar membrane degradation for further application in enzymatic peeling of citrus fruits

AbstractThe enzymatic activity of four commercial enzymatic preparations (Peelzym I, II, III and IV) on citrus pectin, polygalacturonic acid and carboxymethylcellulose was determined (measured as the decrease in relative viscosity). In addition, the effectiveness of these preparations in the enzymatic degradation of the albedo and the segment membrane from Cimboa fruits was assessed. The highest activity on citrus pectin was shown by Peelzym II, although Peelzym I and IV activities were also elevated, 94.5 ± 6.2% and 88.7 ± 8.3% respectively of Peelzym II activity, and no relevant differences were found between them. Peelzym II also showed the highest activity for polygalacturonic acid, which was approximately 25% more than that of Peelzym I and IV, and more than double that of Peelzym III. Peelzym IV showed 40% more EM‐cellulase activity than Peelzym I, II and III. Segment membrane solution was degraded mainly by the enzymatic preparations Peelzym I and II. Thus, the most effective activities for the degradation of the carpelar membrane from Cimboa were those activities which act mainly on pectin and especially on polygalacturonic acid. However, the albedo was degraded to the greatest extent by Peelzym II and, in turn, the most important activities for albedo degradation were those which act on polygalacturonic acid. In addition, the concentration of the enzymatic preparation for the degradation of the carpelar membrane was lower than that required for albedo degradation. Copyright © 2004 Society of Chemical Industry

Effect of Hydrophilically Modified Graft Polystyrene on AOT Oil-Continuous Microemulsions: Viscosifying Effects of P(S-g-PEO) as a Function of Graft Chain Length and Graft Density

The effect of hydrophilically modified polystyrene, poly(styrene-g-poly(ethylene oxide)), P(S-g-PEO), on the viscosity of AOT oil-continuous microemulsions has been investigated as a function of PS and PEO chain lengths and PEO chain density. A series of polymers, P (S-g-PEO) with PEO chain lengths of 23 or 9, and different graft densities were synthesized by living radical polymerization. Thus, a range of polymers with different PS and PEO chain lengths were prepared. Five different microemulsion compositions were studied in an attempt to determine the effect of the microemulsion droplet concentration and droplet size on the viscosity enhancement by the different copolymers. Viscosities were determined at temperatures in the range 25−40 °C. The presence of polymer in the microemulsions always led to increased viscosity relative to the polymer-free microemulsion, the extent of which depended mainly on the polymer composition. Comparisons between the polymers were made in terms of the molar concentration of PEO to take into account differences in the polymer molecular weights and graft densities. A clear correlation was found between the length of the PS chain between grafts and the relative viscosity, with longer PS chains leading to higher viscosities. Increasing the microemulsion droplet concentration resulted in increasing relative viscosity with each of the graft copolymers, because of the shorter interdroplet distances facilitating the formation of active chains. Increasing temperature resulted in a decrease in relative viscosity. Finally, direct comparisons are made between the viscosifying behavior of the graft copolymers and the compositionally similar PEO−PS−PEO triblock copolymers studied previously.

End group modification of polyamide-6 in supercritical and subcritical fluids: Part 2: Amine and carboxylic acid end group modification with 1,2-epoxybutane

The amine and carboxylic acid end groups of polyamide 6 (PA-6) granules were blocked with 1,2-epoxybutane in supercritical or subcritical fluids. The fluids were mixtures of either propane or CO 2 with 10 mol% 1,4-dioxane. Temperatures of 50–140 °C and pressures of 70–80 bars were applied. The reactions were followed in time. The modified polyamide samples were analysed by carboxylic acid end group titrations, by FTIR spectroscopy, by solution and melt viscosity measurements, by DSC and SEC/DV. End group concentrations, relative viscosities and molecular weight distributions (MWD) of modified samples were compared with corresponding values of unmodified PA-6. It was found that better blocking of the end groups was obtained with increasing reaction temperature. However, after modification, at higher temperatures, a decrease in relative viscosity was found. SEC measurements showed that this decrease in relative viscosity not necessarily implies that chain scission had occurred, but that it must be the result of a different interaction of the modified polymer end groups with the solvent. Best results were obtained for PA-6 modified at 100 °C in propane/1,4-dioxane: an improved melt stability was obtained without discolouration of the PA-6 granules or a change in molecular weight, due to the blocking of the amine end groups but leaving the majority of the carboxylic acid end groups unblocked.

Rheology of concentrated suspensions of deformable elastic particles such as human erythrocytes

New models for the viscosity of concentrated suspensions of deformable elastic particles are developed using the differential effective medium approach (DEMA). The models are capable of describing the rheological behavior of un-aggregated suspensions of human red blood cells (RBCs). With the increase in shear rate, a shear-thinning behavior is predicted similar to that observed in the case of un-aggregated suspensions of RBCs. A decrease in relative viscosity and an enhancement of shear-thinning behavior is predicted when either the particle rigidity (elastic modulus) is decreased or the continuous medium viscosity is increased. These predictions are similar to those observed in suspensions of human RBCs. The proposed models are evaluated using experimental data on normal and hardened human RBC suspensions in protein-free saline.

Effect of acetylation on the functional properties of lentil (Lens culinaris) globulin

AbstractThe functional properties of native and acetylated (62.5, 84.1, 90.1 and 93.0%) globulins were evaluated. Acetylation caused a shift in isoelectric pH from 4.5 to 3.5. The solubility of acetylated globulins improved considerably above pH 4.0 but deteriorated below this pH. Increasing acetylation enhanced water absorption (from 1.08 to 1.67, 1.96, 2.29 and 2.33 ml g−1) but reduced oil absorption capacity (from 2.61 to 2.17, 2.15, 2.05 and 1.76 ml g−1). In comparison with native globulin the relative viscosity of acetylated globulins also increased, but with an increase in acetylation level there was a decrease in relative viscosity (2.13, 1.81, 1.65 and 1.62). The emulsifying activity of 62.5% acetylated globulin increased from 54.2% for native globulin to 56.0%, but above this level of acetylation the activity decreased. Emulsion stability followed a similar behaviour. The foaming capacity of native globulin was improved by 62.5% acetylation but reduced at higher acetylation levels. Maximum foam stability was observed for 90.1% acetylated globulin.© 2002 Society of Chemical Industry

Process-Property-Performance Relationship for Fused Deposition of Ceramics (FDC) Feedstock Materials

AbstractFused deposition of ceramics (FDC) is an extrusion based layered manufacturing process. It uses a high solids loaded (>50 vol. % ceramic or metal powder) thermoplastic binder in filament form as the feedstock material. The filament acts as both the piston driving the extrusion process and the feedstock material being deposited in the X-Y direction onto a Z-stage platform. The primary mode of failure of the filament during the FDC process is via buckling. Earlier work has shown that the filament compressive modulus and the feedstock viscosity control the buckling behavior of the filament material in FDC. A study was conducted to investigate the effect of particle/polymer interface on the viscosity and compressive modulus of the PZT filled ECG9 system. The relative viscosity of the untreated and the surface treated particle filled systems increases with solids loading. It is found that both of the surface treated materials (stearic acid and titanate coupling agent) exhibit a lower relative viscosity than the untreated material. A rheological model (Krieger-Dougherty model) was used to investigate the possible reasons for the decrease in relative viscosity due to the surface treatment of particles. The investigaton showed that the coupling agent acted as a dispersant (increasing value of ϕm) and thereby decreased the viscosity. The stearic acid may act as a dispersant (increasing value of ϕm) and as a lubricant (decreasing value of KE). The compressive modulus of all the different systems studied showed an increase with solids loading. A generalized Nielsen model was used to describe the relative modulus vs. solids loading behavior for all the different systems studied. Also, the measured compressive modulus of the filled system was found to be insensitive to the modifications in the particle surface treatment.

Reduction in Viscosity of an SBR Compound Caused by Mastication and Disagglomeration during Mixing

Abstract It would be advantageous to determine the causes of changes in rheological behavior of a compound during mixing, so that mixing times and conditions could be optimized to give the desired processing behavior and properties of the final product. The causes of changes in viscosity during mixing of a compound containing only elastomer and carbon black were investigated by examining concurrent changes in viscosity of the gum, density of the compound and degree of carbon-black disagglomeration. The reduction in viscosity occurring during mixing could be attributed to mastication of the elastomer and disagglomeration of the carbon black. The effect of mastication could be removed by calculating values of relative viscosity, using the viscosity of the gum treated in a similar way to the compound and with an allowance being made for strain-rate amplification. The decrease in relative viscosity of the compound with increased mixing was attributed to a reduction in effective volume fraction of filler caused by immobilized rubber being released as carbon black agglomerates were broken down. The dibutyl phthalate absorption (DBPA) value of the carbon black gave a good indication of the amount of immobilized rubber present in an agglomerate.

Properties of xanthan solutions after long-term heat treatment at 90°C

The thermal stability of two xanthan samples has been studied using light-scattering and viscometry. The experiments were performed in NaCl solutions at concentrations of 1 g/litre, 5 g/litre and 50 g/litre and in a solution containing 5 g/litre NaCl + 1 g/litre CaCl 2. The samples were all O 2-free and the storage temperature was 90°C. Information has been obtained on the time-dependence of relative viscosity, intrinsic viscosity and average molecular weight for storage times up to 6 months. In the solvent containing 1 g/litre NaCl, a rapid decrease in relative viscosity was observed. At this salinity, the xanthan molecule is in its disordered form and the degradation is probably accelerated by chain splitting. In the solvent containing 5 g/litre NaCl, decreases in both the relative and intrinsic viscosities were observed during heat treatment although the degradation is less pronounced than at the lower NaCl concentration. At 5 g/litre NaCl/90°C, the order-disorder transition of xanthan is expected to occur, and degradation is induced when molecules are in the disordered form, which is less stable than the ordered one. The experimental [η] - M w correlation found for heated samples is consistent with the theoretical one for double helix molecules with persistence lengths of 120–150 nm. In the solvent containing 50 g/litre NaCl the transition temperature is notably higher than 90°C and thus the xanthan molecule is in its fully ordered conformation during the whole thermal treatment. Under this condition, no polymer degradation was observed. Both the relative and intrinsic viscosities were found to be unchanged or slightly higher after heat-treatment of several months. In the solvent containing 5 g/litre NaCl + 1 g/litre CaCl 2 the intrinsic viscosity characteristics were the same as for the 50 g/litre NaCl-solvent. The slight rise in intrinsic viscosity observed after 2–3 months of heat treatment might be attributed to an extension of the backbone of the xanthan molecule.

Effect of High Doses of Gamma Rays on Corn Grains. Part II. Influence on Some Physical and Chemical Properties of Starch and Its Fractions

AbstractSolubility, swelling power, viscosity, alkali number and ferricyanide number were estimated in the starch isolated from both irradiated air‐dried and moist corn grains. An increase in solubility, alkali number and ferricyanide number and decrease in relative viscosity were found in starch isolated from irradiated air‐dried as well as moist corn grains as the dose level was raised. The swelling power increased up to 2 megarad, then decreased rapidly. Infrared analysis revealed an additional absorption band which arises from a new methylene group at 5 megarad. An increase in amylose percentage concomitant with a decrease in amylopectin percentage was found as the radiation dose was increased up to 2 megarad. Above 2 megarad, the opposite was found. The chain length of amylose and amylopectin showed a progressive decrease as the irradiation dosage was raised.

Specific cleavage of the native Type III collagen molecule with trypsin: Similarity of the cleavage products to collagenase-produced fragments and primary structure at the cleavage site

Solutions of native Type III collagen (chain composition, [ α1( III)] 3) exhibit a rapid and dramatic decrease in relative viscosity when incubated with trypsin. Cleavage products of the reaction were precipitated with ammonium sulfate and isolated in denatured form by molecular sieve chromatography. They were found to be comprised of: α1(III)-T1 (molecular weight, 71,000) derived from the NH 2-terminal portion of the Type III molecule; and α1(III)-T2 (molecular weight, 24,000) from the COOH-terminal portion of the molecule. Determination of the amino acid sequence at the NH 2-terminal portion of α1(III)-T2 as well as at the COOH-terminus of α(III)-T1 demonstrated that the products arose from specific cleavage of the type III molecule at an arginine-glycine bond corresponding to residues 780–781 in the repetitive triplet sequence of the α1(III) chain. The results suggest that the trypsin-susceptible bond in the native Type III collagen molecule resides in a region characterized by a relative lack of the normal collagen helicity.

Cartilage collagen: Inability to serve as a substrate for collagenases active against skin and bone collagen

Human gingival and rabbit polymorphonuclear leukocyte collagenases previously shown to be active against native monomeric skin and bone collagen, with the chain composition [α1(I)] 2α2, do not cleave native monomeric cartilage collagen, with the chain composition [α 1(II)] 3, as measured by a decrease in relative viscosity. Both types of collagen, however, are actively degraded by collagenase (EC 3.4.4.19) obtained from Clostridium histolyticum. The results strongly support the suggestion that collagen in cartilaginous structures is resorbed by a mechanism independent of that utilized in other tissues.

Photodegradation of cis‐1,4‐polyisoprene sensitized by the addition of chloronitroso compounds

AbstractIt was found that chloronitroso compounds with a free non‐conjugated nitroso group show a considerable sensitizing activity in respect to the process of photochemical degradation of dissolved cis‐1,4‐polyisoprene, which is induced by visible radiation (4000–7000 A.). The effect of 10 chloronitroso sensitizing compounds were investigated. The highest sensitizing activity was found with compounds 2,2‐chloronitrosopropane and 1,1‐chloronitrosocyclohexane. The maximum wavelength, of which the decrease of relative viscosity of solutions was the highest, was determined for 2,2‐chloronitrosopropane. The highest sensitizing activity of chloronitroso compounds was found for wavelengths corresponding to the absorption maximum of the sensitizer added. The theory of the sensitizing activity of chloronitroso compounds is proposed.