Dynamic Surface Tension Research Articles

Effect of surfactants and interfacial rheology on equilibrium drop size in turbulent liquid-liquid dispersions

Surfactants are often required to stabilize liquid-liquid dispersions produced by high shear mixers. Due to the high power input, drops are deformed rapidly in the dispersion zone so the dynamic interfacial properties governed by the surfactant adsorption rate can have a significant impact on the resulting drop size. The objective of this work is to develop a fundamental link between surfactant adsorption dynamics, interfacial properties, and turbulent emulsification processes. To ensure constant bulk surfactant concentration during dispersion, equilibrium drop size for dilute dispersions produced by a batch rotor-stator mixer were studied. Silicone oils of various viscosity were dispersed in aqueous nonionic surfactant solutions. Drop size distributions (DSD) were measured via a video microscopy/automated image analysis technique. Equilibrium interfacial tension was measured via a pendant drop technique, as a function of surfactant concentration. The dynamic surface tension was similarly measured. The data were fit to the Langmuir adsorption isotherm and the long-times approximation to the Ward – Tordai equation and the adsorption parameters and surfactant diffusivities so obtained were employed, with an estimate of the drop deformation timescale, to estimate the surface dilational modulus (Esd) or Marangoni stress acting on the drop’ surface due to interfacial tension gradients. Trends observed in the measured equilibrium mean drop size and DSD are explained in terms of the interfacial and rheological properties. Below the CMC, Esd peaks and the drop size increases with bulk surfactant concentration, despite a decrease in equilibrium interfacial tension. Above the CMC, Marangoni stresses are small but the presence of the surfactant still modifies the rheology of the interface, increasing the effective viscosity of the drops. A comprehensive set of mechanistic models for drop size in turbulent flows, based on Kolmogorov-Hinze theory, was developed and modified to partially account for the effect of surfactants via an appropriately defined effective viscosity. The approach allows integration of surfactant phenomena into widely accepted correlations for drop size in surfactant free systems.

The characterization of Pluronic P123 micelles in the presence of sunscreen agents.

The triblock copolymer Pluronic® is widely used in the personal care industry, including sun protection, for its film-forming and solubilization capabilities. In this study, the effect of three commonly used organic UV filters (ethylhexyl methoxycinnamate [EMC], ethylhexyl triazone [EHT], and avobenzone [AVB]) on the structure of Pluronic P123 micelles was investigated. The Pluronic P123 micelle structure has been investigated using dynamic surface tension, nuclear magnetic resonance (NMR) and small-angle neutron scattering (SANS). Dynamic surface tension results show strong interactions between the UV filters and Pluronic® evident by sharp changes in the surface activity of the latter. The NMR results have revealed the creation of a hydrophobic microenvironment special to the Pluronic PPO core group in the presence of UV filters. Some interaction with the hydrophilic EO was also recorded, albeit weaker. This is further confirmed by SANS, where the Pluronic P123 micelles interacted with varying strengths with the UV filters, resulting in sharp changes in their size and shape. We have demonstrated the sensitivity of the Pluronic P123 micelles to the presence of various UVA/B filters. The micelles shape varied from spherical to cylindrical as the concentration and type of the UV filters were varied. These variations in the shape are expected to have a significant effect on the sun protection factor (SPF), as it affects the solubilization of the UV filters within a formulation in addition to the formulations' rheological profile and film-forming behaviour.

Dynamic surface stress field of the pure liquid-vapor interface subjected to the cyclic loads.

We demonstrate a methodology for computationally investigating the mechanical response of a pure molten lead surface system to the lateral mechanical cyclic loads and try to answer the following question: how does the dynamically driven liquid surface system follow the classical physics of the elastic-driven oscillation? The steady-state oscillation of the dynamic surface tension (or excess stress) under cyclic load, including the excitation of high-frequency vibration mode at different driving frequencies and amplitudes, was compared with the classical theory of a single-body driven damped oscillator. Under the highest studied frequency (50GHz) and amplitude (5%) of the load, the increase of in (mean value) dynamic surface tension could reach ∼5%. The peak and trough values of the instantaneous dynamic surface tension could reach (up to) 40% increase and (up to) 20% decrease compared to the equilibrium surface tension, respectively. The extracted generalized natural frequencies seem to be intimately related to the intrinsic timescales of the atomic temporal-spatial correlation functions of the liquids both in the bulk region and in the outermost surface layers. These insights uncovered could be helpful for quantitative manipulation of the liquid surface using ultrafast shockwaves or laser pulses.

Adsorption dynamics of quaternary-ammonium-salt–based gemini and trimeric surfactants with different spacer structures at air/water interface

The dynamic surface tensions of gemini surfactants with spacers containing cyclic structures such as diethylene and triethylene chains, and atoms such as oxygen and nitrogen, and of linear- and star-type trimeric surfactants with spacers having propylene or hexylene chains between the quaternary ammonium groups (for the linear-type) and propylene or hexylene chains between the quaternary ammonium group and the central amino group (for the star-type) were measured using the maximum bubble pressure method. The effects of the molecular structures and surfactant concentration on the maximum rate of reduction in the surface tension as well as the diffusion coefficient were elucidated. The gemini surfactants containing cyclic structures in the spacer exhibited slower interfacial adsorption, which was ascribed to their rigid spacer structure. The longer the spacer chain length of the gemini surfactants, the greater the molecular flexibility and hence the faster the adsorption at the interface. Thus, the diffusion and adsorption of gemini surfactants are affected by the rigidity and hydrophobicity of the spacer, respectively. However, the adsorption of the trimeric surfactants at the air/water interface (which resulted in a maximum rate of reduction in the surface tension of 0.0007–0.004 mN m–1 s–1) was lower than that of the gemini surfactants (which resulted in a maximum rate of reduction in the surface tension of 0.0009–0.9 mN m–1 s–1). This was ascribed to the greater bulkiness of trimeric structures compared with those of the gemini surfactants. The star-type trimeric surfactants adsorbed faster at the air/water interface than the linear-type trimeric surfactants because the former were flexible despite their bulky spacer structure. For the linear- and star-type trimeric structures, the diffusion rate increased with the spacer chain length because of the resulting increase in the molecular flexibility. The linear-type surfactants were adsorbed faster at the air/water interface as their spacer chain length was increased, whereas the star-type surfactants were adsorbed more slowly because of their molecular bulkiness.

SOME FEATURES OF CAPILLARY WAVE ENERGY CONVERSION ON LIQUID SURFACE IN THE PRESENCE OF DYNAMIC SURFACE TENSION

The effect of dynamic surface tension on capillary oscillations of a droplet is studied in the theoretical asymptotic calculations of the first order of smallness with respect to the dimensionless amplitude of oscillations of charged droplets of a polar liquid. The calculations are carried out within the framework of a model of an ideal incompressible electrically conducting liquid. It has been shown that allowance for the effect of dynamic surface tension increases the order of the dispersion equation, which acquires one more damping root relevant to the destruction of the near-surface electrical double layer (disordering of molecules in the near-surface layer). What is interesting about the revealed damping is that it takes place in an ideal liquid, while the characteristic damping time coincides with that measured experimentally. Free energy transformations occur between mechanical, thermal, electromagnetic, and mechanical again forms of energy, with all of the transformations being caused by the effect of the dynamic surface tension. It has been shown that the dynamic surface tension has a weak effect on the low-frequency oscillations of the droplets, while it essentially affects the high-frequency oscillations causing their rapid damping.

DYNAMIC SURFACE PROPERTIES OF FIBRIN

Fibrin is formed via polymerization of one of the main blood proteins, fibrinogen, under the action of an enzyme, thrombin. Dynamic surface elasticity and dynamic surface tension of mixed solutions of fibrinogen and thrombin are measured as functions of surface age and enzyme concentration (50–800 U/L). The nonmonotonic pattern of the dependences for the dynamic surface elasticity indicates the multistage character of fibrin film formation and makes it possible to monitor the transition from unfolded protein to individual filamentous aggregates; a network of branched fibrils; and, finally, a continuous film. The dynamic surface elasticity of fibrin films is twofold higher than the corresponding values for fibrinogen (115 and 55 mN/m, respectively). The use of different types of microscopy makes it possible to assess the morphology of the obtained films.

Fabrication, characterization and emulsifying properties of agarose microgel

Agarose microgels were prepared with bottom-up approach, and emulsifying properties of agarose microgels were investigated. Physical properties of microgels are varied with agarose concentration, and further affect the emulsifying performance of microgels. Enhanced surface hydrophobicity index and decreased particle size of microgels were recorded with the increasing of agarose concentration, which were conducive to emulsifying properties of microgels. Improved interfacial adsorption of microgels was evidenced by Dynamic surface tension and SEM. However, microscopic morphology of microgel at O/W interface indicated that increasing agarose concentration could weaken the deformability of microgels. The influence of external conditions (pH and NaCl) on the physical properties of microgels were investigated, and their effects on emulsion stability were evaluated. Compared with acidification, NaCl was appeared to be more destructive to emulsion stability. Results indicated acidification and NaCl could decrease surface hydrophobicity index of microgels, but there was differentiation in the variation of particle size. It was inferred that deformability of microgels could make contribution to the stability of emulsion. This study verified that microgelation was a feasible scheme to improve the interfacial properties of agarose, and the influence of agarose concentration, pH, and NaCl on the emulsifying performance of microgels was investigated.

Surface tension behavior of superspreading and non-superspreading trisiloxane surfactants

One parameter frequently considered to be relevant for superspreading of trisiloxane surfactants is surface tension kinetics. In the scientific literature, some experimental results reported for trisiloxane surfactants are in contradiction with fundamental concepts of surfactant monomer diffusion. Therefore, maximum bubble pressure tensiometry has been used to determine dynamic surface tension (DST) of two types of trisiloxane surfactants: superspreader and non-superspreader. Results show that both surfactants behave similarly at concentrations below critical micelle concentration (CMC), as expected. The CMC curves, as determined by drop shape analysis, confirmed that the more hydrophilic non-superspreader has a higher CMC as compared to the more hydrophobic superspreader. Accordingly, the lower surfactant monomer concentration of the superspreader results in a higher DST than the non-superspreader at the same surface age. So, in contrary to claims in the literature, there is nothing mysterious or unexpected concerning the surface tension behavior of trisiloxane surfactants.Graphical

The effect of buffer concentration on the dynamic/equilibrium surface tension of bovine serum albumin solution

The effect of phosphate buffer (Na2HPO4 and NaH2PO4) concentration on the dynamic and equilibrium surface tension (ST) of bovine serum albumin (BSA) solutions was examined in this study. A pendant bubble tensiometer was utilized for measuring the ST relaxation of BSA solutions in varying buffer concentration (0, 0.01–300 mM). The data showed: (i) an initial increase in buffer concentration (Cbuff < 0.3 mM) resulted in a slower ST relaxation and a notable rise in the equilibrium ST; (ii) a further rise in buffer concentration (Cbuff > 0.3 mM) resulted in a faster ST relaxation and a progressive decrease in the equilibrium ST; and (iii) despite an increase in BSA concentration from 2 to 15 (10−10 mol/cm3), the dynamic ST of BSA solutions always relaxed the slowest at Cbuff = 0.3 mM. The equilibrium ST of BSA solutions in 10 and 44 mM buffer [C = 0.1–15 (10−10 mol/cm3)] was also obtained and the data confirmed the near-constant equilibrium ST of purely aqueous BSA solutions [Le et al., J.Mol.Liq (2022) 118305] to not be an anomalous behavior but, observable irrespective of the solvent formulation.

Interaction enhancement of Lyocell cellulose chains for controlled fibrillation behavior with greener application in eco-textiles

Lyocell is treated as a biodegradable, sustainable, and low-carbon emission cellulose fiber, but it possesses a high fibrillation tendency in the dyeing process which is generally conducted at alkaline, wet and high-temperature conditions. The fibrillation phenomenon seriously reduces the product quality and affects its application in eco-textiles. In response to the problem, a greener and simple fibrillation prevention treatment was innovatively conducted before the coloration process to enhance the interaction of Lyocell cellulose macromolecular chains. A nonionic crosslinker with isocyanate reactive groups was applied for the fibrillation control. The mechanism of the reaction between the nonionic crosslinker and Lyocell cellulose chains was determined through the measurements of fiber swelling, dynamic surface tension, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). It was found that the fibril interaction was significantly enhanced with reduced lateral swelling of Lyocell fibers. The fibrillation tendency was greatly reduced at the treatment condition of 20 g/L, 175 °C, and 80 s. Moreover, the interaction between cellulose chains was further improved after dyed with bifunctional reactive dyes. In comparison to commercial cationic and anionic crosslinkers, the nonionic sample not only showed little effect on the dye fixation, but also added good wrinkle resistance to Lyocell fabrics. The method showed the advantages of a shorter process and low chemical consumption compared to the conventional Lyocell dyeing process. Therefore, this work may promote the development of Lyocell fabric in high-quality and eco-friendly textiles.

Influence of acetylene bond on surface activity of acetylenic diols in aqueous solutions

Acetylenic diol surfactants, named after the carbon–carbon triple bond known as the acetylene bond, exhibit good dynamic surface tension and foam-free properties. They are widely used as wetting agents and molecular defoamers in industry and research. Although the role of the hydrophilic and hydrophobic moieties of these surfactants are well characterized, the effect of the acetylene bond on their surface activity has not yet been elucidated. To this end, herein, the chemical structure, equilibrium surface tension, dynamic surface tension, and foam properties of an alkyne free diol, SC14 diol, were analyzed and compared with those of an acetylenic diol, Surfynol 104. An increase in the rate of diffusion of the surfactant from water–air surfaces was observed when the acetylene bond existed. The performance of both diols as surfactants was discussed. The unique performance of SC14 diol surfactant enhances its potential applicability value in the field of ink and paint manufacturing.

Analysis of mixed prostate specific antigen and Tween-20 sessile droplets for the reduction in interfacial PSA adsorption

The effect of non-ionic surfactants (Tween-20) in droplet-based systems where a prostate-specific antigen (PSA) laden droplet is placed on an anti-PSA immobilized PDMS substrate was investigated. The role of surfactants in such (antibody-antigen system with surface reaction) droplet-based systems has not been studied before and there are no studies involving surfactant-protein-colloids in droplet-based systems with surface reaction, and this is the motivation of the present work. In this article, we investigated the interactions between protein-surfactant-colloid systems in evaporating sessile droplets with antibody-antigen surface reactions using dynamic surface tension (DST), micro-PIV and confocal microscopy. The presence of Tween-20 showed dampening of the velocities in systems with surface reaction even though the Marangoni number was observed to increased. The dynamic surface tension curves of the pure Tween-20 samples were higher than those of the mixed samples (Tween-20+PS+PSA), indicating the influence of Tween-20 and its contribution to interfacial tension reduction. With an increase in the bulk concentration of Tween-20, the surface tension relaxations also increase implying that more surfactant molecules are transported to the interface and get adsorbed there leading to more homogeneous distribution of the surfactant, PS and PSA. The deposition patterns were homogeneous at all Tween-20 concentrations which is desired in biosensors. The results from this study can be useful for designing biosensors with reduced non-specific binding and lesser interfacial adsorption by incorporating the optimum concentration of Tween-20 in the droplets.

A microfluidic study of bubble formation and coalescence tuned by dynamic adsorption of SDS and proteins

During foaming, bubbles are formed at (sub)millisecond time scales, and emulsifier adsorption determines bubble formation and stabilisation against coalescence. Here we introduce a microfluidic device, in which bubbles are formed in two distinct pressure regimes at low versus high pressures, and emulsifier adsorption can be inferred from the easily-monitored dynamics of bubble formation and coalescence, as well as the bubble properties. We studied dynamic adsorption for various types and concentrations of emulsifiers, namely sodium dodecyl sulfate (SDS; 0.05–3% wt.) and various proteins (5% wt.) including whey protein isolate (WPI), β-lactoglobulin (β-lac), and bovine serum albumin (BSA). The results show that as SDS concentration increases up to 3% wt., the bubble formation time decreases in the low-pressure regime due to the enhanced adsorption of SDS, yet increases in the high-pressure regime due to the promoted ‘dripping-jetting’ transition; in both pressure regimes the neck thinning process slows down, leading to longer bubble growth time and thus larger bubble size. To suppress coalescence of bubbles formed at time scales down to 10 μs, SDS is the most efficient, followed by BSA, WPI, and finally, β-lac; this is ascribed to the dynamics of emulsifier adsorption, e.g., the resulting dynamic surface tension. To conclude, our microfluidic study highlights the dynamic effects in the presence of SDS and proteins during bubble formation, even at high concentrations. This means that to explain the properties of a freshly-formed foam product, it is crucial to understand (and thereafter manipulate) emulsifier adsorption at time scales relevant to bubble formation and coalescence.

Equilibrium and dynamic surface properties of cationic/anionic surfactant mixtures based on alcohol ether sulfate

The equilibrium and dynamic surface properties of anionic surfactant alcohol ether sulfate with different EO distribution(C-AE2S and N-AE2S) and cationic surfactant tetradecyltrimethylammonium bromide (TTAB) mixtures under different molar ratios were investigated. Their surface activities, adsorption, and spreading performances were investigated by static/dynamic surface tension measurements, molecular dynamics simulation, and dynamic contact angle techniques at 298 K. The static surface tension analysis reveals that the critical micellization concentration (cmc) values and the surface tension at cmc (γ cmc) of the binary systems are much lower than that of the individual component. Compared with C-AE2S/TTAB, N-AE2S/TTAB systems have higher cmc and lower γ cmc. It was found from the molecular dynamics simulation that negative charges of C-AE2S were drastically neutralized by the positively-charged TTAB at the interface in the system of C-AE2S/TTAB. The dynamic surface tension results indicate that the adsorption process of aqueous solutions for both C-AE2S/TTAB and N-AE2S/TTAB are mixed diffusion-kinetic adsorption mechanisms. From the dynamic contact angle measurements, it could be obtained that the mixtures exhibit better spreading behavior than that of the individual component and N-AE2S/TTAB systems have lower contact angles than that of C-AE2S/TTAB at the same mixing ratios.

On the adsorption kinetics of an eco‐friendly surfactant n‐decyl‐β‐D‐maltopyranoside

AbstractEco‐friendly surfactant alkyl polyglycosides (APGs) have garnered ample interest in the literature. However, the adsorption kinetics of APGs at an air‐water interface has not been studied to date. Consequently, this study aimed at investigating the adsorption kinetics of the APG n‐decyl‐β‐D‐maltopyranoside (β‐C10G2) at a freshly created air‐water interface. The dynamic and equilibrium surface tension (ST) of the aqueous β‐C10G2 solutions were experimentally measured at varying concentrations using a pendant bubble tensiometer and the ST data were examined via theoretical simulations using the Langmuir and Frumkin models. The fitting results revealed that the Frumkin model (with K = −2.9) well‐predicted the equilibrium ST data; signifying a considerable cohesive intermolecular force amidst the adsorbed β‐C10G2 molecules. The theoretical mixed‐controlled ST profiles (predicted by the Frumkin model) described the dynamic ST data reasonably well, but the adsorption rate constant increased significantly at increasing concentration. A comparison on the ST data of β‐C10G2 and β‐C12G2 (n‐dodecyl‐β‐D‐maltopyranoside) was also conducted and a relatively greater surface‐activity and lower cmc of the latter alkyl glycoside was observed.

Impact of Natural-Based Viscosity Modifiers of Inhalation Drugs on the Dynamic Surface Properties of the Pulmonary Surfactant

The effectiveness of inhalation therapy depends on aerosol size distribution, which determines the penetration and regional deposition of drug in the lungs. As the size of droplets inhaled from medical nebulizers varies depending on the physicochemical properties of the nebulized liquid, it can be adjusted by adding some compounds as viscosity modifiers (VMs) of a liquid drug. Natural polysaccharides have been recently proposed for this purpose and while they are biocompatible and generally recognized as safe (GRAS), their direct influence of the pulmonary structures is unknown. This work studied the direct influence of three natural VMs (sodium hyaluronate, xanthan gum, and agar) on the surface activity of the pulmonary surfactant (PS) measured in vitro using the oscillating drop method. The results allowed for comparing the variations of the dynamic surface tension during breathing-like oscillations of the gas/liquid interface with the PS, and the viscoelastic response of this system, as reflected by the hysteresis of the surface tension. The analysis was done using quantitative parameters, i.e., stability index (SI), normalized hysteresis area (HAn), and loss angle (φ), depending on the oscillation frequency (f). It was also found that, typically, SI is in the range of 0.15-0.3 and increases nonlinearly with f, while φ slightly decreases. The effect of NaCl ions on the interfacial properties of PS was noted, which was usually positive for the size of hysteresis with an HAn value up to 2.5 mN/m. All VMs in general were shown to have only a minor effect on the dynamic interfacial properties of PS, suggesting the potential safety of the tested compounds as functional additives in medical nebulization. The results also demonstrated relationships between the parameters typically used in the analysis of PS dynamics (i.e., HAn and SI) and dilatational rheological properties of the interface, allowing for easier interpretation of such data.

Surface activity of N-graphene quantum dot in presence of CTAB surfactant

An interface can be subtly engineered utilizing nanoparticle-surfactant interactions by controlling surface activity and surface charge balancing. In this research, the effect of N-doped Graphene Quantum Dot particles (N-GQDs) and Cetyl trimethylammonium bromide surfactant (CTAB) presence in the air/water interface is explored. We found on the study of interplay of N-GQD with CTAB that N-GQDs are surface active particles. Thereafter, the effect of concentration ratio of CTAB to N-GQD on surface tension and elasticity is investigated up to critical micelle concentration (CMC). The results demonstrate the surface activity of N-GQDs when there is no surfactant molecules (1 wt% N-GQD, surface tension (ST) ∼53). In addition, the results manifest that due to CTAB molecules' attachment to the N-GQD particles, more efficient surface-active mixtures are created. At higher surfactant loadings, the excess CTAB monomers compete with CTAB/ N-GQDs mixtures to reach the interfaces, causing mixture to come back into the bulk of liquid verified by elasticity evaluations. The preparation of N-GQDs and as a result its mixture includes economical and easy experimental protocols, and according to the synergistic effects defeat the individual components constraints i.e. –at 1% N-GQD+0.25 CMC CTAB the dynamic surface tension lies below pure CTAB CMC line.

Synthesis and physicochemical properties of sodium oleyl sulfate

Abstract In this paper, sodium oleyl sulphate (SOS) was successfully synthesised by reacting octyl alcohol (OA) with gaseous sulphur trioxide (SO3) as a sulphating reagent in a falling film reactor. The structure was determined by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1HNMR) spectroscopy. The dynamic adsorption and aggregation behaviour of SOS was systematically investigated to reveal the relationship between the structure and properties of SOS. The physicochemical properties of SOS were determined by measuring the equilibrium surface tension, dynamic surface tension and dynamic contact angle, respectively. A laser particle size analyser and a transmission electron microscope (TEM) were used to analyse the aggregation behaviour of SOS. Compared to sodium dodecyl sulphate (SDS) and sodium n-octadecyl sulphate (C18H37OSO3Na), which have a similar structure to SOS, the increase in hydrophobic chain size and tighter molecular packing enabled by the polar head conformation caused a decrease in CMC and an increase in surface activity. The efficiency of the surface activity was controlled by a mixed diffusion kinetic adsorption mechanism. Moreover, SOS in aqueous solution showed efficient wettability on the surface of the low-energy paraffin film at concentration above the CMC. In addition, SOS molecules can spontaneously form spheroidal aggregates with increasing concentration, and the size of the aggregates increased with the concentration.

Enhanced interaction of dye molecules and fibers via bio-based acids for greener coloration of silk/polyamide fabric

Multi-component fabrics combined with natural silk fibers and man-made polyamide fibers are good choices for high-quality textile owing to the remarkable comfort and excellent resistance. The silk/polyamide fabric colored with reactive dyes generally shows good fastness, but the problems still remain that large dye effluent discharge, high chemical consumption, and long-time dyeing process. To counter these issues, herein we report a greener coloration method without any salt or alkali added for the coloration of silk/polyamide fabrics. Three bio-based acids like acetic acid, citric acid, and tannic acid were introduced into the dye solution to improve the interaction of dye molecules and fibers. Much of the focus has been given to understand the mechanism between the dye molecules, bio-based acids and fibers, which was determined through dynamic surface tension and UV–visible absorption spectrum measurement. Through this, it was found that the citric acid due to its maximum number of carboxyl groups than acetic acid and tannic acid promoted the disaggregation of dyes and enhanced the dye diffusion to fiber surface. As a result, the dye fixation and color strength of silk and polyamide fibers were all significantly improved when using citric acid at pH 6 with the steaming for 5 min. From the SEM analysis, it was seen that the surface morphology of silk/polyamide fibers was not so much affected. Compared with the traditional dyeing method, this method exhibited enhanced color performance with a shorter dyeing process, lower chemical consumption and nice fastness property. This work presented a potential and practical application of natural additives in the dyeing of multi-component fabrics to achieve eco-friendly and high-quality textile products.

Dynamic interfacial properties and foam behavior of licorice root extract solutions

Licorice (Glycyrrhiza glabra) is a useful plant of the family Fabaceae, with sweet-tasting roots. The root extract of this plant is rich in saponins, so it can be considered a source of natural surfactants. This research provides some applicable information about the dynamic surface tension and foam behavior of aqueous solutions of licorice root extract (LRE). The pendant drop shape analysis was utilized to study the surface tension and dilational surface rheology of LRE at the water/air interface. The Bikerman type experiment was used to measure foamability and foam stability of aqueous LRE solutions. The equilibrium surface tensions reveal that the LRE contains surface-active components and is capable of reducing the surface tension by 25 mN/m at the critical aggregation concentration (CAC). The surface dilational visco-elasticity measurements proved that the adsorption layers are predominantly of elastic nature. Also the foamability and foam stability show a meaningful correlation with the dynamic surface properties. This study aims to contribute to the development of appropriate utilization of the benefits provided by a biosurfactant source in foam-related commercial applications.