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How to measure Antifoaming Agents’ Effectiveness with FOAMSCAN™
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Although liquid foams are thermodynamically unstable, under practical conditions they can remain stable for long periods, often creating significant challenges across various industries. To achieve low foamability or low foam stability, specific additives are used to either prevent or destroy foam formation.
FOAMSCAN™ can accurately quantify the effectiveness of antifoaming agents through controlled foam generation and decay analysis. A Defoamer X was tested at four concentrations (25–500 ppm) in two surfactant systems. Foams were produced by gas sparging, and the time to reach a target foam volume measured foamability, while foam half-life indicated stability... in this study, FOAMSCAN™ provided a reliable, quantitative, and automated method to evaluate both foamability and foam stability, making it an ideal tool for screening and optimizing antifoaming additives in surfactant-based formulations.
How to measure the interfacial properties of solid oils with TRACKER™
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The solidifying properties of oils are harnessed in a wide range of industrial, food, cosmetic, and pharmaceutical applications. These properties stem from the ability of certain oils to crystallize, harden, or form solid structures under specific conditions, such as temperature changes or interactions with other substances.
However, measuring the surface tension of such oils can be challenging due to their solidifying nature, specially when their melting point is high. To address this, the TRACKER™ drop tensiometer is equipped with a specialized syringe holder that allows the sample to be heated both in the syringe and at the needle tip, ensuring accurate measurements.
To demonstrate the capabilities of the TRACKER™, the surface tension of three solid oils (coconut oil, butter, and paraffin wax) was measured at both the air-oil and water-oil interfaces...
Characterizing foams produced by an external device
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Hands disinfection particularly arose over the covid19 sanitary crisis. Because they are convenient in use and cost-effective, foam dispensers are commonly used to deliver hands- disinfectant in the form of foam.
For hands- disinfectant manufacturers, it is of the utmost importance to control the volume of foam delivered by the dispenser and the properties of the foam, such as stability or texture, when it is mashed in the hands.
The foam analyzer FOAMSCAN™ enables to characterize the foam properties of foams, generated by dispensers, by measuring 2 key parameters: liquid fraction and foam structure (size and distribution of the bubbles)...
The influence of experiment settings on foaming capacity
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This note illustrates how experimental settings directly impact the foaming properties of liquids analyzed with the FOAMSCAN™.
Foams were produced either by gas sparging or by mechanical stirring.
For gas sparging, the gas flow rate and glass frit porosity were found to strongly affect foaming time and foam wetness, while the initial liquid volume had little influence. Smaller frit pores produced slower but wetter foams.
For mechanically stirred foams, both stirring speed and liquid volume were critical: low speed led to slow foaming, while too high speed consumed all liquid.
The study demonstrates that foam generation settings must be carefully selected to ensure reproducible and meaningful results.
Standard error, five reasons you should check the drop profile
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The TRACKER™ drop tensiometer relies on analyzing the shape of a Laplacian drop; any deviation introduces calculation errors. Therefore, the TRACKER™ evaluates the residuals between the theoretical Laplace profile and the actual drop contour to detect such deviations.
Five typical non-Laplacian cases are described: mechanical vibrations, profile interruptions by bubbles or dust, air bubbles trapped in drops, solid interfacial films, and moving profiles. Each case produces a characteristic residual pattern that helps diagnose the measurement problem.
Residual analysis is a quick, reliable quality control step for accurate interfacial measurements using the pendant or rising drop methods.
Interfacial Rheology , A Tool to Probe Interfaces
While surface tension quantifies adsorption and interfacial activity, it cannot fully describe interfacial behavior. Two systems with the same surface tension can exhibit very different macroscopic properties.
By applying sinusoidal oscillations to the interfacial area, the interfacial viscoelastic modulus (E)* is determined, with its elastic (E′) and viscous (E″) components revealing molecular mobility and relaxation. For example, SDS and water/IPA mixtures have similar surface tensions but distinct interfacial responses: SDS shows strong viscoelastic behavior, while IPA does not.
This technique thus distinguishes between interfaces that are merely surface-active and those with significant elastic or viscous response, key for foam and emulsion stability. Interfacial rheology is therefore essential to link molecular-scale interactions to macroscopic properties like stability and texture in foams, emulsions, and dispersions...
Impact of frequency, amplitude and concentration on interfacial viscoelastic modulus
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The interfacial viscoelastic modulus depends on three key experimental parameters: oscillation frequency, amplitude, and solution concentration. Using the TRACKER™, measurements were performed on interfaces stabilized by proteins, polysaccharides, and bitumen emulsions.
At low amplitude or frequency, molecules have time to diffuse and reorganize; at higher frequencies, interfaces behave more elastically. Increasing frequency raises the elastic modulus (E′) but decreases the viscous modulus (E″), consistent with diffusion-limited adsorption models. The amplitude effect shows that large deformations can weaken the interfacial network, particularly in plant–dairy protein blends. The concentration effect often follows a bell-shaped curve, with maximum elasticity at intermediate surface coverage.
The study concludes that E* is not an intrinsic material constant but depends on the mechanical solicitation regime, emphasizing the need for well-defined measurement protocols.
Interfacial rheology: micro and macro illustrations
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This note links molecular-scale interfacial properties to macroscopic foam and emulsion stability.
Surface-active molecules impart elastic and viscous behavior to interfaces, quantified by the interfacial viscoelastic modulus.
At the microscopic level, measuring E′ and E″ helps monitor molecular adsorption, reaction dynamics, or particle desorption (e.g., COâ‚‚-induced chitosan destabilization). At the macroscopic scale, systems with higher surface elasticity show greater stability against coalescence, drainage, and Ostwald ripening. In emulsions, rigid interfacial films correlate with enhanced long-term stability (≥30 days).
Overall, interfacial rheology bridges molecular interactions and bulk material properties, providing a a powerful parameter for the characterization of fluid/fluid interfaces.
Dispersity: an indicator to classify the foam dissipation
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Foam struture analysis can distinguish foam dissipation mechanisms.
FOAMSCAN™ was used to generate Two foams, A and B, under identical conditions and analyzed over 1800 seconds.
The dispersity (D), defined as the ratio of bubble-size standard deviation to mean radius, was tracked over time.
Foam A maintained a constant dispersity, indicating coarsening (Ostwald ripening) as the main aging mechanism.
Foam B showed an increasing dispersity, typical of coalescence-driven foam decay.
These results show that dispersity is a powerful indicator to classify foams according to their dissipation mechanisms.
The deposition of a monolayer of phospholipids at the oilwater interface
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In many areas, monolayers are at the crossroad of interfaces between immiscible phases forming emulsions. There are different types of monolayers which can be surfactants molecules, like lipids, polymers, proteins, asphaltenes, solid particles… Generally one of the 2 immiscible phases is water and the other can be natural oil, alkane of variable chains or volatile solvent like chloroform, toluene… Lipid droplets [1] are organelles consisted of a core of neutral lipids (triglycerides, sterol esters, liposoluble vitamins and a monolayer of phospholipids in which proteins are embedded (involved in regulation, structure, synthesis and lipid mobilization)...
How to control the surface pressure of an interface
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Using the TRACKER™ drop tensiometer, phospholipids were adsorbed at an oil/water interface, and surface pressure was adjusted by compressing or expanding the drop area. Increasing the surface area dilutes the monolayer, raising surface tension, while compression increases phospholipid packing and lowers it.
After adsorption equilibrium, sequential expansions and compressions allowed the creation of interfaces with different controlled pressures ranging from 5 to 28 mN/m.
This method enables the study of adsorption, desorption, and rheological properties of interfacial films under variable pressures. The approach is particularly relevant for modeling biological membranes and lipid droplets, where phospholipids govern interfacial stability.
How to determine the maximum surface pressure of a molecule
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The maximum surface pressure (ΠMAX) defines the limit beyond which an adsorbed molecule is ejected from an interface.
Using the TRACKER™ drop tensiometer, proteins were adsorbed at an oil/water interface and subjected to successive compression and expansion cycles. Changes in surface tension (Δγ) were recorded to assess whether molecules remained adsorbed or desorbed.
For protein A, ΠMAX = 14.6 mN/m, indicating desorption at moderate pressure, while protein B remained strongly bound. This parameter ranks molecules by interfacial affinity and mechanical stability.
The method enables detailed analysis of molecular adsorption–desorption dynamics, crucial in biology, cosmetics, and emulsified systems...
How to determine the surface exclusion pressure of a molecule
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The surface exclusion pressure (Πâ‚‘) represents the maximum pressure above which a molecule can no longer insert into a lipid monolayer.
Using the TRACKER™ tensiometer, an oil/water interface was coated with phospholipids, and proteins were injected at different surface pressures. The additional pressure caused by protein adsorption (ΔΠ) was measured; when ΔΠ = 0, adsorption ceased, identifying Πâ‚‘.
This parameter quantifies the affinity of biomolecules for lipid interfaces, influenced by lipid charge, phase state, and subphase conditions.
The method provides insight into molecular insertion mechanisms and protein–lipid interactions.