Drop Weight Method Research Articles

Medidas de tensão superficial pelo método de contagem de gotas: descrição do método e experimentos com tensoativos não-iônicos etoxilados

Surface tension knowledge of surfactants aqueous solutions is important during amphiphilic molecule manufacturing and new product development, as feedback information to handle synthesis parameters to target performance. Drop counting method is an interesting simplification of drop weight method for surface tension measurements. A simple laboratory measurement device, with capability for temperature control, was assembled to allow investigation of ethoxylated surfactants. The implementation of the method was preceded by a detailed investigation of two factors that may affect the measured surface tension: drop formation velocity and surfactant ethoxylation degree. The limitations of the method are discussed on this basis.

A CRITICAL REVIEW: SURFACE AND INTERFACIAL TENSION MEASUREMENT BY THE DROP WEIGHT METHOD

The drop weight method has been used as a standard method for surface and interfacial tension measurement. However, lack of appropriate guidelines in using this method has resulted in errors. The specific objective of this critical review is to present the experimental setup, the limitations on the correction factors, and the principle of the drop weight method. Mathematical models of correction factors were evaluated by using a proposed error analysis. The use of the proposed Lee-Chan-Pogaku model and HG-Equation 2 for correction factor determination is suggested. However, further investigations would be required to justify the validity of the correction factors at low r/V 1/3 range and their use for viscous fluids. The physics of drop detachment is complicated; more investigations would be required to form a rigid theory of this method.

Variations of Interfacial Tension of the n-Butyl Acetate + Water System with Sodium Dodecyl Sulfate from (15 to 22) °C and pH between 6 and 9

Interfacial tension of n-butyl acetate + water + sodium dodecyl sulfate is reported over the aqueous surfactant concentration range of (0 to 34.68·10−5) mol·L−1, the temperature range of (15 to 22) °C, and the pH of 6 to 9. The measurements were performed by the drop-weight method, using a narrow capillary with very thin thickness. The interfacial tension values ranged from (15.8 to 4.5) mN·m−1, and the data show a good agreement with Szyszkowski’s equation as the surfactant concentration varies. The variation of interface concentration and the area occupied by each molecule of surfactant shows that surface coverage decreases as the pH increases. The interfacial pressure, entropy, and enthalpy values are derived, and their variations are investigated versus appropriate parameters.

Highly filled natural CaCO3 composites, III. Filler surface treatment and its structure

Particulate polymer composites have become attractive owing to their widespread applications. For some, it is desired to obtain properties of interest through the use of high loadings without limiting the processability or degrading the mechanical properties of the material. Improved properties and higher solid loading can be achieved using surface active agents. The current work deals with the structure and properties of interfaces in highly filled particulate composites based on natural CaCO3 particles and polydimethylsiloxane (PDMS) as a binder. A series of fatty acids was used to modify the surface properties of the filler, changing the interfacial properties and better understand the relationship between the interface structure and the rheological and mechanical behavior of the studied systems. This part of the work describes the surface properties and surface energy characterization of the raw and fatty acids treated filler, studied by inverse gas chromatography and the wicking method. The neat and treated prepolymer was studied using an improved drop weight method and the polymer films surface properties were studied using the contact angle method. It is shown that the fatty acids' hydrocarbon chains dissolve in the prepolymer, and segregate to the surface of the polymerized film. The interface structure was analyzed as follows: the adsorbed layers composition through gas chromatography and thermogravimetric analysis; the adsorbed layers structure through differential scanning calorimetric analysis and the surface chemistry by XPS. It is shown that the adsorbed fatty acids arrange in an ordered structure characterized by an apparent melting peak.

The effect of viscosity on surface tension measurements by the drop weight method

AbstractViscosity is one of the parameters affecting the measured surface tension, as fluid mechanics affects the measurement process using conventional methods. Several methods including the selected planes (SPM) and WDSM which combines the weight drop method (WDM) and SPM, are applied to surface tension measurement of high viscous liquids. Yet, none of them treats the viscosity effect separately. The current publication presents a simple, easy to apply empirical approach of satisfactory accuracy, for evaluation of surface tension of liquids having wide range of viscosities up to 10 Pa s. The proposed method is based on Tate's law and the “drop weight” method using calibration curves of known liquids having similar surface tensions but different viscosities. Drop weight of liquids having viscosity ≥0.05 Pa s, was found to be significantly affected by the liquid viscosity. The shape factor, f, of high viscosity liquids was found to correlate linearly with the logarithm of viscosity, pointing the importance of viscosity correction. The experimental correlation presented in the current work can be used as a tool for the evaluation of surface tension for high viscosity liquids such as prepolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

ナノ粒子濃厚スラリーの曳糸性と粒子凝集構造

Aggregate structure of fine particles and thread forming property of thick slurry was investigated. Slurries could be classified into three states of aggregate structure depending on the dispersant concentration. The rheological behavior of slurries was determined by the aggregate structure of fine particles. The relationship between the dispersion state of particles and the surface tension were measured by a drop weight method. As a result, the thread forming property of thick slurry is reflected on the surface tension and apparent viscosity, and therefore measurement of surface tension and apparent viscosity may give the information on particle dispersion state.

Experimental analysis of the effect of some compaction methods on mechanical properties and durability of cement stabilized soil

Cement stabilized soil is usually compacted by different mechanical methods to increase its strength and durability. This paper summarizes the results of an experimental study on the effect of different compaction methods on the performance of stabilized soil. The compaction methods investigated were either static compaction by applying a static pressure using an universal compression testing machine, dynamic compaction by a drop weight method, or static compaction coupled with vibration. All methods were applied on unstabilized soil or cement stabilized soil. The effect of each method of stabilization on compressive strength, shrinkage and water resistance are reported. Dynamic compaction with about 8% of cement content seems to give the best performance for the soil investigated.

Adsorption at liquid interfaces: The generalized Frumkin isotherm and interfacial structure

The thermodynamics of adsorption of amphiphilic surface-active compounds at the interface between two immiscible liquids is considered. At the interface, these molecules are supposed to replace a few of the adsorbed molecules of both solvents. Classical isotherms of adsorption (Frumkin, Frumkin-Damaskin, Langmuir, Henry) were based on the model of non-penetrable interface, where an adsorbate can substitute only molecules of one solvent. At the interface between two immiscible electrolytes, nonpolar oil/water interfaces, and liquid membranes amphiphilic molecules can substitute molecules of both solvent and classic isotherms cannot be used. The generalization of Frumkin isotherm for permeable and non-permeable interfaces, known as the Markin-Volkov isotherm, gives the possibility to analyze adsorption in a general case. The adsorption isotherms of pentafluorobenzoic acid at the octane/water interface at different pHs were measured by the drop-weight method. The thermodynamic parameters of pentafluorobenzoic acid (PFBA) adsorption at octane/water interface were determined. From the measurements of PFBA adsorption, the structure of the octane/water interface was determined. Substitution of one adsorbed octane molecule requires approximately three adsorbed PFBA molecules. This result shows that the orientation of solvent molecules at the interface is different from the bulk. Adsorbed octane molecules have a lateral orientation with respect to the interface. Gibbs free energy of adsorption equilibrium and thermodynamic parameters of PFBA adsorption show that the adsorption of PFBA at the octane/water interface is accompanied by a reduction in the attraction between adsorbed PFBA molecules as the pH decreases to the acidic region.

Structural Health Monitoring of Fiber-reinforced Composite Plates for Low-velocity Impact Damage using Ultrasonic Lamb Wave Tomography

The feasibility of imaging low-velocity impact damage in thin multi-layered composite plates using Lamb wave tomography is explored. Low-velocity impact damages (6-20 J) are induced by the drop-weight method on graphite fiber epoxy matrix composite laminates of cross-ply and quasi-isotropic lay-up and the damage assessment is carried out by conventional C-scans and ultrasonic Lamb wave tomography. Lamb wave based tomography based on modified cross-hole sensor configuration is used to image the damage as a function of impact energy for graphite composite plates. The reconstructed tomograms are able to capture the lateral extent of the damage even for impact energies as low as 11 J in a 2 mm graphite epoxy quasi-isotropic lay-up sample that can be classified as barely visible impact damage.

Adsorption at Liquid Interfaces: The Generalized Langmuir Isotherm and Interfacial Structure

The thermodynamics of adsorption of amphiphilic surface-active compounds at the interface between two immiscible liquids is considered. At the interface, these molecules are supposed to replace a few of the adsorbed molecules of both solvents. Classical isotherms of adsorption (Frumkin, Langmuir, Henry) were based on the model of nonpenetrable interface, where an adsorbate can substitute only molecules of one solvent. However, at the interface between two immiscible electrolytes, like nonpolar oil-water interfaces, or liquid membrane amphiphilic molecules can substitute molecules of both solvents; therefore, classical isotherms are not applicable in these cases. The generalization of Langmuir and Frumkin isotherms for permeable and nonpermeable interfaces, known as the Markin-Volkov (MV) isotherm, gives the possibility to analyze adsorption and the interfacial structure in a general case. In the present paper, the adsorption isotherms of pentafluorobenzoic acid at the octane-water interface at various pH were measured by the drop-weight method. The thermodynamic parameters of pentafluorobenzoic acid (PFBA) adsorption at the octane-water interface were found. From the measurements of PFBA adsorption, the structure of the octane-water interface was determined. Substitution of one adsorbed octane molecule requires approximately three adsorbed PFBA molecules. This result shows that the orientation of solvent molecules at the interface is different from the bulk solution. Adsorbed octane molecules have a lateral orientation with respect to the interface. Gibbs free energy of adsorption equilibrium and thermodynamic parameters of PFBA adsorption show that the adsorption of PFBA at the octane-water interface is accompanied by a reduction in the attraction between adsorbed PFBA molecules as the pH decreases to the acidic region.

Do Polysaccharides Such as Dextran and Their Monomers Really Increase the Surface Tension of Water?

It has been reported in the literature that sugars such as dextrose and sucrose increase the surface tension of water. The effect was interpreted as a depletion of the solute molecules from the water-air interface. This paper presents accurate measurements of the surface tension of different concentrations of dextrose solution as well as its polymer (i.e., dextran). An automated drop shape technique called axisymmetric drop shape analysis (ADSA) was used for the surface tension determination. The surface tension measurement is presented as a function of a shape parameter, P(s), which has been used to quantify the range of the applicability of ADSA. The results of the above study show that dextrose solutions decrease the surface tension of water in contradiction to the results obtained from the weight drop method in the literature. The surface tension decreases continuously with increasing concentration. A similar effect was observed for the dextran solutions. To verify that the setup and the methodology are capable of accurately measuring increases in surface tension, a similar experiment was conducted with a sodium chloride solution with a concentration of 1 M. It is well-known that electrolyte solutions, e.g., sodium chloride, increase the surface tension of water. The results obtained from ADSA verify that the sodium chloride increases the surface tension of water by 1.6 mJ/m(2). It is concluded that dextrose and dextran decrease the surface tension of water. Thus, there is no evidence of depletion. To identify the sources of discrepancy between the results of ADSA and those reported in the literature, the experiments were repeated for different concentrations and the rate of drop formation using the drop weight method. It was found that the rate of drop formation is most likely the source of error in the results reported in the literature.

Analysis of the drop weight method

The drop weight method is an accurate yet simple technique for determining surface tension σ. It relies on dripping a liquid of density ρ at a low flow rate Q̃ from a capillary of radius R into air and measuring the combined volumes of the primary and satellite drops that are formed. The method’s origin can be traced to Tate, who postulated that the volume Ṽideal of the drop that falls from the capillary should be given by ρgṼideal=2πRσ, where g is the gravitational acceleration. Since Tate’s law is only an approximation and the actual drop volume Ṽf<Ṽideal, in practice the surface tension of the liquid-air interface is determined from the experimental master curve due to Harkins and Brown (HB). The master curve is a plot of the fraction of the ideal drop volume, Ψ≡Ṽf∕Ṽideal, as a function of the dimensionless tube radius, Φ≡R∕Ṽf1∕3. Thus, once the actual drop volume Ṽf, and hence Φ, is known, σ is readily calculated upon determining the value of Ψ from the master curve and that Ψ=ρgṼf∕2πRσ. Although HB proposed their master curve more than 80 years ago, a sound theoretical foundation for the drop weight method has heretofore been lacking. This weakness is remedied here by determining the dynamics of formation of many drops and their satellites in sequence by solving numerically the recently popularized one-dimensional (1–d) slender-jet equations. Computed solutions of the 1-d equations are shown to be in excellent agreement with HB’s master curve when Q̃ is low. Moreover, a new theory of the drop weight method is developed using the computations and dimensional analysis. The latter reveals that there must exist a functional relationship between the parameter Φ, where Φ−3 is the dimensionless drop volume, and the gravitational Bond number G≡ρgR2∕σ, the Ohnesorge number Oh≡μ∕(ρRσ)1∕2, where μ is the viscosity, and the Weber number We≡ρQ̃2∕π2R3σ. When We→0, the computed results show that Φ depends solely on G. In this limit, a new correlation is deduced which has a simple functional form, G=3.60Φ2.81, and is more convenient to use than that of HB. The computed results are also used to show how the original drop weight method can be extended to situations where We is finite and resulting drop volumes are not independent of Oh.

Preparation and physical properties of novel nonionic surfactants and their grafting copolymers with linear low density polyethylene (LLDPE)

AbstractThree nonionic surfactants, S1, S2, and S3 and their acrylates, AS1, AS2, and AS3, were synthesized with poly(ethylene oxide) and diols such as glycol, 1,6‐hexanediol, and 1,10‐decanediol as the main starting materials. Their chemical structures were characterized by means of Fourier transform infrared (FTIR) spectroscopy and 1H NMR. The surface activity and surface tension (γ) of S1, S2, and S3 were evaluated by a drop weight method. The surface tension was found to decrease with the length of the lipophilic spacer in the molecular chains (γS1 < γS2 < γS3). AS1, AS2, and AS3 were adopted as functionalizing monomers and grafted onto linear low density polyethylene (LLDPE) with a melt reactive extrusion procedure. The graft degrees of LLDPE were determined by FTIR. Three grafted LLDPE samples with grafting degrees of 1.16% (AS1), 0.82% (AS2), and 0.71% (AS3) were prepared. Thermal and rheological properties of grafted LLDPE samples were studied with differential scanning calorimetry and a rotational rheometer. Crystallization rates of grafted LLDPE were faster than that of plain LLDPE at a given crystallization temperature because graft chains could act as nucleating agents. The isothermal crystallization behavior of grafted LLDPE was in accordance with the Avrami model only in the first stage, and deviated from the model with an increase in the crystallization time. Shear thinning at high shear rates and shear thickening at low shear rates were observed for the grafted LLDPE. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 314–322, 2005

Evaluation of the effects of some additives and pH on surface tension of aqueous solutions using a drop-weight method

In the present study a simple drop-weight method was used as a technique to measure the surface tension of various aqueous solutions. A newly modified version of the Harkins–Brown correction factor was proposed in order to improve the accuracy of the drop-weight method. The applicability of this newly proposed correction factor was tested with various aqueous solutions, i.e., sucrose, NaCl as well as acetic acid solutions, and it was found that the deviation between the calculated and standard values of surface tension of these solutions was less than 2.5%. The technique was then used to study the effects of selected additives and pH on the surface tension of aqueous solutions. The results showed that addition of hydrocolloids decreased the surface tension of the solutions to various extents while addition of tapioca starch did not affect the surface tension of the suspension. It was also found that the type of acid used to adjust the pH affected the surface tension of aqueous solutions differently although the pH of the solutions was equal.

A fundamental study of dry and wet grinding in bending tests on glass—effect of repeated impact on fracture probability

The preparation of fine powders by grinding may be accomplished either by wet or dry processes, the differences between these have been discussed. It is well known that there are many mechanical properties which have direct effects upon the grindabilities of solids, breaking properties in particular. In addition, the difference of breaking strength in different atmospheres is also known. In this study, dynamic bending tests were carried out, using a drop weight method, on glass, to assess the quantitative effect of a water atmosphere on fracture probability. The influence of the crack length on the glass surface and repeated impact on the difference of fracture probability in water and in air was also studied. As a result, it was found that the fracture probability in water was larger than that in air when the crack length of the glass surface and the input energy to the specimen were constant. The above difference increased with decreasing crack length and input energy to the specimen. It was confirmed that a wet grinding process is useful from the point of view of fracture energy.

A Multipurpose Apparatus To Measure Viscosity and Surface Tension of Solutions. The Measurement of the Molecular Cross-Sectional Area of n-Propanol.

A multipurpose apparatus is described that can be used to measure the viscosity of a solution by the Ostwald method and the surface tension by either the capillary-rise or the drop-weight method. The apparatus allows for measurement of a set of solutions (obtained by dilution of initial concentration) without reloading each solution. The apparatus can also be used to measure the properties of a solution that exibits surface foaming. The deviation of measured values by the apparatus is less than 3.5%.

Adaptação no método do peso da gota para determinação da tensão superficial: um método simplificado para a quantificação da CMC de surfactantes no ensino da química

The discussion based on surfactant cleaning action is commonly used in chemistry classrooms for the comprehension of theoretical concepts related to surface tension and micelle formation. The experimental quantification of surface tension of aqueous solutions of surfactants provides the practical instruments for this discussion. The present paper describes a simplification on the common apparatus employed for the drop-weight method, making the determination of surface tension accessible to any chemistry lab. The surface tension of various liquids and the critical micelle concentration, CMC, of three commercial surfactants were measured with this modified method, and proved to be consistent with literature values.

Interfacial Tension of Saturated Butan-1-ol + Sodium Dodecyl Sulfate + Saturated Water from 20 to 50 °C and at a pH between 4 and 9

The liquid−liquid equilibrium interfacial tension of binary systems of saturated butan-1-ol and water has been studied over the aqueous surfactant (sodium dodecyl sulfate) concentration range of 0 to 3.48 × 10-4 mol·L-1 (0 to 100 ppm), the pH range of 4 to 9, and the temperature range of 20 to 50 °C. The measurements were made by the drop-weight method. No previous data were found in the literature for the effect of surfactant and pH. The experimental data show a linear decrease with increasing surfactant concentration and temperature; however, the pH reduces the interfacial tension nonlinearly. The interfacial pressure was also obtained from data. The experimental values were correlated by empirical equations.

Surface Tension Measurements on Industrial Alloys by the Drop-Weight Method

The drop-weight method has been successfully applied to a representative set of industrial alloys (W–Re26, Mo–Re50, Pt–Rh10, Pt–Rh30, Ti–Al6–V4, AISI 316 L stainless steel, INCONEL 182 and 600 alloys), with the result that very reproducible surface tension measurements (Δ σ/σ<0.5%) have been established for these materials at the liquidus temperature. This work supports the idea that the simplicity of the drop-weight method should attract much more attention for production control or to provide reference values at the liquidus temperature, although it cannot be used for temperature coefficient measurements of the surface tension.

Performance of compacted cement-stabilised soil

Earth construction is widespread in desert and rural areas because of its abundance and cheap labour and could be an alternative construction material for low cost housing in Algeria. However, earth construction suffers from shrinkage cracking, low strength and lack of durability. This paper reports on the Algerian experience on earth construction in housing and gives an extended review of an experimental study to investigate a stabilised soil by either mechanical means such as compaction and vibration and/or chemical stabilisation by cement. Soil used was characterised by its grading curve and chemical composition. Compaction was either applied statically or dynamically by a drop weight method. A mixture of sand and cement was also tried. The effect of each method of stabilisation on shrinkage, compressive strength, splitting tensile strength and water resistance are briefly reported. The experimental results showed that the best method of stabilisation of the soil investigated, which gives a good compressive strength and a better durability at a reasonable cost, could be a combination of a mechanical compaction and chemical stabilisation by cement or sand and cement up to a certain level.