Various Rates Of Shear Research Articles

Effect of enzymatic treatment of starch gelatinized with urea

The present work is undertaken with a view to discover the effect of enzymatic hydrolysis using α-amylase enzyme on different kinds of starches. This was done while starch was in the gelatinized form under the action of urea at room temperature. To achieve this goal, maize starch was subjected to gelatinization using urea at room temperature under different conditions. The latter comprise, starch concentration, urea concentration, pH value, time and temperature as well as the concentration of α-amylase enzyme. The modified starches were evaluated via measuring the solubility and the apparent viscosity at various rates of shear. The modified starches were evaluated as thickeners in printing wool fabrics with acid dye and polyester using disperse dye. The results of these investigations demonstrated that the concentration of starch increases from 30 to 40 to 50g%, the apparent viscosity increases regularly irrespective of the rate of shear. The apparent viscosity increases by increasing the amount of urea. Increasing of α-amylase enzyme concentration is accompanied by a decrease in the apparent viscosity at any specific rate of shear. The most suitable pH for starch modification by enzyme was found at pH 7.The temperature highly influences the apparent viscosity of maize starch at any specific rate of shear. However 80◦C can be considered as the optimum temperature in enzymatic modification of maize starch to obtain soluble starch which acquire a suitable viscosity. Generally speaking enzymatic treated starches give better results in direct printing when compared with Daico-thic or mypro gum.

Effect of enzymatic treatment of starch gelatinized with sodium hydroxide

Different Kinds of starches were subjected to gelatinization under the action of sodium hydroxide solution at room temperature and treated with alpha-amylase enzyme in the gelatinized form. To achieve this goal, maize starch was subjected to gelatinization using sodium hydroxide at room temperature under different conditions. The latter comprise, starch concentration, sodium hydroxide concentration, pH value, time and temperature as well as the concentration of α-amylase enzyme. The modified starches were evaluated via measuring the solubility and the apparent viscosity at various rates of shear. The modified starches were evaluated as thickeners in printing wool fabrics with acid dye and polyester using disperse dye. The results of these investigations demonstrated that increasing the apparent viscosity by increasing starch concentration is expected. The apparent viscosity increases by increasing the amount of sodium hydroxide.Increasing of α-amylase enzyme concentration is accompanied by a decrease in the apparent viscosity.The most suitable pH for starch modification by enzyme was found at pH 7.The temperature highly influences the apparent viscosity of maize starch at any specific rate of shear. However 50◦C is the most suitable degree for modification of maize starch to obtain a suitable viscosity and cold water solubility and also avoid the higher decrease in the viscosity. The treated starches were evaluated via measuring the solubility and rheological properties.

Technological Evaluation of Acrylic Acid /Cassia Saligna Gum Grafted products as Thickener in Textile Printing

Galactomannan gum extracted from Cassia Saligna seeds was subjected to graft copolymerization using acrylic acid. Thegraft copolymerization has been performed using potassium persulphate as initiator.The rheological property of the grafted product and it is utilization as a thickening agent in printing cotton fabrics with reactive dyes was thoroughly investigated. The rheological properties and theviscosity at various rates of shear were investigated. Furthermore, the results obtained indicate that grafted product gum could be used safely as a thickener in printing of cotton fabric, using silk screen printing instead of the commercial thickener of sodium alginate.

Preparation and Characterization of Methylcellulose Derivatives from Cellulosic Wastes

Cellulosic wastes from El-Nasr Co. for Intermediate Chemicals are used as a starting material for the preparation of methylcellulose with tailored properties. The wastes are first purified, followed by alkali ageing for different intervals of time. This is done to control the molecular weight of the cellulose molecules, thereby obtaining cellulosics with different degrees of polymerization (DP). These samples along with the original purified cellulose are methylated under similar conditions and the obtained methylcellulose samples are examined for solubility, degree of substitution (DS) and rheological properties. The results obtained from these investigations are summarized as follows. It is found that the DP of the starting cellulose progressively decreases by prolonging the duration of alkali ageing, while the carboxyl content increases. The DS of the methyl groups increases as the DP of the starting substrate decreases. The rheological properties as well as the apparent viscosity at various rates of shear for the prepared derivatives are thoroughly investigated.

Synthesis and characterization of hypochlorite oxidized poly (methacrylic acid)-starch composites

Maize starches were independently polymerized with methacrylic acid (MAA) to different levels and their behaviour towards hypochlorite oxidation was examined and compared with native and initiator-treated starches. Synthesis of poly (MAA) starch composites was performed using a potassium permanganate/citric acid initiation system. Hypochlorite treatment was carried out using sodium hypochlorite at a concentration of 3 and 10 g/l active chlorine, for 15–60 min at 50 °C and pH 9. The oxidation reaction was studied with respect to chlorine consumption and carboxyl content as well as apparent viscosity at various rates of shear. Application of these composites before and after hypochlorite treatment to cotton fabric was also carried out to evaluate their suitability as sizing agents. The results are discussed with respect to the structure of the original starch and the poly (MAA)-starch composite.

Shear and normal stresses of a poly( vinyl alcohol)/sodium borate aqueous solution at the start of shear flow

The shear stress, σ, and the first normal stress difference. N 1, at the start of shear flow with various rates of shear, γ, were measured for a 2% aqueous poly( vinyl alcohol) solution containing 1% sodium borate (PVA/B). Reduced stresses, σ/γ and N 1/γ 2, increased slightly with γ and leveled off to steady values when γ was less than a certain critical value, γ c. At very high rates of shear, the reduced stresses increased significantly with γ and kept on increasing with time until the flow became unstable. At moderate γ just above γ c, the reduced stresses exhibited a tendency to level off over quite a long period and then started to increase again. At any rate of shear, the stress relaxed rapidly on cessation of the flow. This observation may be interpreted by the assumption of enhanced rate of Borax-ol complex formation in highly oriented PVA chains in flow, and the slowing down of the relaxation of chain orientation trapped in the temporarily crosslinked network formed by the complex of finite lifetime.

Oxidation of maize and rice starches using potassium permanganate with various reductants

Maize and rice starches were independently treated with potassium permanganate in presence of the reductants citric acid, oxalic acid and sodium sulphite under various conditions of pH, temperature, time, liquor ratio and permanganate concentration. The treated starch samples were monitored for carboxyl and carbonyl contents as well as apparent viscosity at various rates of shear. This treatment yields mixed type oxidized starch because it contains both carboxyl and carbonyl groups, the amounts depending upon the conditions. The apparent viscosity of the starch decreases on oxidation, the rate increasing with increase in rate of shear. Maize starch is more susceptible to oxidation than rice starch. When applied as sizing agents for cotton textiles, oxidized starches display a better performance than the unoxidized starch.

Cyanoethylation of Hydroxyethyl Cellulose: Preparation and Characterization

Abstract Commercial hydroxyethyl cellulose (HEC) was cyanoethylated with acrylonitrile in nonaqueous medium in the presence of sodium hydroxide under a variety of conditions. Variables studied included the amount of acrylonitrile and the reaction temperature. The reaction was proved by NMR and its extent was measured by determining the nitrogen content. The physical properties of the obtained derivatives—i.e., the electric properties and the apparent viscosity at various rates of shear—were investigated. It was found that the extent of reaction was increased by increasing the amount of acrylonitrile as well as the reaction temperature. The products were water soluble and their apparent viscosity increased with increasing nitrogen content. The same holds true for the dielectric constant and dielectric loss.

Oxidation of Hydroxyethyl Cellulose with Sodium Hypochlorite

Abstract Oxidation of water-soluble hydroxyethyl cellulose with sodium hypochlorite has been studied under a variety of conditions. Variables studied included the concentration of sodium hypochlorite, pH, temperature, and catalyst. It was found that the rate of oxidation was increased by increasing the hypochlorite concentration and/or reaction temperatures. The rate is very slow in an alkaline medium and very rapid in neutral medium. The effect of catalyst on the rate of oxidation was also investigated. The apparent viscosities of the oxidized samples at various rates of shear were also investigated.

Equilibrium Curve and Constant Structure Curve for Thixotropy of Polyvinylchloride Solutions in Dibutylphthalate

According to the phenomenological theory for thixotropy presented by Cheng and Evans, an equilibrium curve and constant-structure curves can be determined as characteristic shearing stress vs. rate of shear relations for a thixotropic liquid. These curves were obtained by measuring the shearing stress at various rates of shear with a Weissenberg rheogoniometer using two solutions of polyvinylchloride in dibutylphthalate. Solutions of constant structure are non-Newtonian; shearing stress goes to zero as rate of shear approaches zero. Solutions in equilibrium state of structure are suggested to have yield stress. Relaxation spectra of these solutions at various rates of shear were determined from stress relaxation after cessation of steady flow. These results were discussed in relation to the hypothetical formation and destruction of structure in the solution. An empirical equation for the shear-rate dependence of shearing stress of these solutions was derived by analysing the data. This equation is consistent with the Cheng-Evans' constitutive relation for thixotropic liquids.

Shear Stress Overshoot during Constant-Rate Shearing of Polyvinylchloride Solutions in Dibutylphthalate

Development of shearing stress after the onset of simple shearing flow of two thixotropic solutions of polyvinylchloride in dibutylphthalate was measured at various rates of shear with a Weissenberg rheogoniometer. The sample solution was sheared at a rate of shear γ0 until steady-state stress was reached, and subsequently left to stand still for a length of time t0. Then rate of shear was changed to a new value γ and transient shearing stress was measured. This procedure was repeated for different combinations of γ0, γ and t0. When γ0<γ, stress overshoot appeared even for vanishingly small t0, and the maximum stress increased with increasing t0 over the range of t0 greater than one month. When γ0>γ. stress overshoot appeared only for t0 greater than a few days. In this case, increase of stress overshoot with t0 was small as compared with the case γ0<γ. These results were discussed from the view point of formation of structure in the solution during to and destruction under shear. Finally, effect of t0 on stress overshoot was compared with the theoretical calculations based on the Bogue model for non-linear viscoelasticity

On the Viscosity of Liquid Selenium

Abstract The viscosities of liquid selenium and partially-chlorinated liquid selenium were measured in the temperature range from 235°C to 305°C using an Ubbelohde-type tilting viscometer. The “intrinsic” viscosities, η0, were estimated by extrapolating the values of the viscosities, ηθ, of various rates of shear to a zero rate of shear. The “intrinsic” viscosities of the liquid selenium were estimated to be 20.18, 13.46, 9.11, 6.32, 3.67 and 2.30 poise at 235, 245, 255, 265, 285, and 305°C respectively. The viscosities of the chlorinated liquid selenium decreased with an increase in the chlorine content, but they varied discontinuously at a chlorine content of 0.0125% and then decreased linearly. The apparent activation energy for the viscous flow of the liquid selenium was estimated to be 17.9 kcal/mol. The apparent activation energies for the viscous flow of the chlorinated selenium varied discontinuously at a chlorine content of about 0.0125%, as in the case of the viscosity. The average-chain length of the selenium molecules was considered not to be changed, but the radicals at both ends of the linear chain vanish in forming the bonds with chlorine atoms with an increase in the chlorination below a chlorine content of 0.0125%. Therefore, it is concluded that the presence of radicals at the molecular ends would have an influence upon the viscosity and the apparent activation energy for the viscous flow of selenium. The notable large value of the apparent activation energy of such a non-branched polymer as selenium was attributed to the large amount of energy needed to transport the segments into the holes.

Experimental Studies on Fluidity of Grouting Paste for Prestressed Concrete

The qualities necessary for the grouting paste for prestressed concrete are faculty of smooth flow, little bleeding and change of volume, high strength (compressive and bond) and resisting power for freezing. But those qualties, excepting the faculty of flow, are improved by the minimum use of water.The current apparatus for measurement of fluidity of grouting paste are such as shown in Fig. 1∼Fig. 3, either of which is used, according to the enquête undertook by the Dutch Grouting Committee, in various foreign countries except in Holland.The“International Recommendation”arranged by the same Committee has recently stated that“The water-cement-ratio must be as low as possible for a good workability. The fluidity of the grout may be measured with every kind of apparatus that gives reproducible results. Every type of apparatus must be calibrated in poises.”But no apparatus has been calibrated in poise so far.It is partly due to the thixotropic property of cement paste but mainly to the assumption that cement paste is nothing but a Newtonian liquid. The experiments which the writers have made with his coworkers on an assumption that cement paste is Bingham body clearly show that the measurements done with those apparatus can be expressed in terms of absolute unit.The measurement has been done by means of BH type rotation viscometer (Photo. 1) at various rates of shear, that is, its number of rotation of rotor.Investigation has also been made as to the change which the charactaristic values of ηpl and ν undergo by taking into consideration various conditions necessary for the presstressed concrete grouting, that is, mix proportion, types and numbers of rotation of mixer, mixing time and the fineness of cement.Several results are shown in the following figures. From these experiments some conclusions have been obtained as follows:(1) Cement paste behaves as Bingham body, and the fluidity of grouting paste is represented both by ηpl and ν.(2) The values of these rheological properties are influenced by mixproportion, types and numbers of rotation of mixer, mixing time and the fineness of cement etc..(3) The current apparatus for measurement of fiuidity of paste which are shown in Fig. 1∼ Fig. 3 will not be sufficient for measurement of ηpl and ν.

Effects of Rate of Shear on Inherent and Intrinsic Viscosities of Polystyrene Fractions

Fractions of polystyrene, varying in molecular weight from 0.3×106 to 10×106 approximately, were prepared by careful tertiary fractionation. Inherent viscosities were determined at various rates of shear in the approximate range 100–20 000 sec−1, viscosity measurements being made at several different temperatures in benzene and toluene (good solvents for polystyrene), in butanone (an intermediate solvent), and in cyclohexane (a poor solvent). From these values intrinsic viscosities at various rates of shear were determined. These viscosity functions are sensitive to shear rate at high molecular weights; at a given temperature the shear effects are greater the higher the molecular weight and the better the solvent, and with increasing temperature they decrease in a good solvent and increase in a poor one This behavior is shown to be consistent with current ideas regarding the size and shape of polymer molecules in solution as affected by weight, temperature, and solvent power. It is concluded, among other things, that with flexible polymers (or polymer fractions) of very high molecular weight, measurements of intrinsic viscosity should be made in a poor solvent at a low temperature.

Mechanism of Reënforcement. III. Viscosity of Carbon Black Suspensions in GR-S Solutions

Abstract The viscosity of carbon black suspended in GR-S solutions has been investigated in a Stormer-type viscometer at various rates of shear. Relative viscosities thus determined have been extrapolated to zero rate of shear and, by applying Einstein's viscosity equation, the volume of the suspended particles has been calculated. It has been found that, under the conditions examined, the carbon black particles are surrounded by a rubber layer 150 to 200 Ångstroms thick.

Mechanism of reinforcement III: Viscosity of carbon black suspensions in GR‐S solutions

AbstractThe viscosity of carbon black suspended in GR‐S solutions has been investigated in a Stormer‐type viscosimeter at various rates of shear. Relative viscosities thus determined have been extrapolated to zero rate of shear and by applying Einstein's viscosity equation the volume of the suspended particles has been calculated. It has been found that under the conditions examined the carbon black particles are surrounded by a rubber layer 150 to 200 Ängstroms thick.

A RHEOLOGICAL STUDY OF SOLUTIONS OF NITROCELLULOSE

By using a MacMichael viscometer the change in viscosity at various rates of shear was determined for solutions of various types of nitrocellulose in the solvents; acetone, n-butyl acetate, Hercules' mixed solvent, and dibutyl phthalate. It was found that all solutions of low intrinsic viscosity nitrocellulose were dilatant in dilute solution, while those of high intrinsic viscosity were thixotropic. Thixotropy also changed with concentration, the solutions studied going from dilatant to thixotropic through Newtonian types on increasing the concentration. Thixotropy and dilatancy were both found to decrease as the temperature increased. At a given concentration, both the viscosity and the structural viscosity of solutions varied with solvent, dibutyl phthalate giving both the highest viscosity figures and the greatest effect on structural viscosity.