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1.
H. L. Lew 《Journal of the American Oil Chemists' Society》1967,44(6):359-366
A tandem “acid” pyrolysis-capillary chromatographic method for analyzing surfactants has been developed, and its application
to the more common anionic and nonionic surfactant types investigated. In this method a surfactant is mixed with an acid,
such as P2O5 or H3PO4, and dropped into a pyrolyzer attached to a capillary gas chromatograph. The resulting volatile pyrolyzate is carried into
the chromatograph for analysis.
According to the chromatograms, the point of cleavage during “acid” pyrolysis is quite selective, usually at a C-S or C-O
bond. For example, LAS and ABS give peaks corresponding to the alkylbenzene precursors; primary linear alkyl sulfates and
sulfonates, peaks corresponding to olefins with the same number of carbon atoms as the alkyl group; and alcohol and alkylphenol
ethoxylates and ethoxylate sulfates, peaks corresponding to olefins from the alkyl group and to acetaldehyde and a higher
aldehyde from the polyethoxy group. Alkylphenol derivatives are probably cleaved to form an alkylphenoxy intermediate, which
then dealkylates to give the olefins.
This method is quantitative for carbon number or carbon number and isomer distribution of hydrophobes in linear surfactants,
semiquantitative for ethoxy content and for hydrophobes in branched chain surfactants, and qualitative for hydrotropes and
certain foam additives. Surfactants, as well as mixtures of certain surfactant types, in built detergent formulations can
be analyzed without isolation.
Winner, Bond Award Medal, Philadelphia, October 1966. 相似文献
2.
S. Takano C. Takasaki K. Kunihiro M. Yamanaka 《Journal of the American Oil Chemists' Society》1977,54(4):139-143
A method (DMF-Methylate method) has been described for the homolog analysis of cationic and amphoteric surfactants having
a quaternary am-monium group. The homolog distribution of cationic and amphoteric surfactants obtained by the DMF-Methylate
method closely agrees with that of the original alkyldimethylamines used. Therefore, the DMF-Methylate method should be applicable
to the homolog analysis of these surfactants. This method also offers qualitative information for the identifica-tion of these
surfactants, since the ratio of the α-olefin to the alkyldimethylamine varies with each sur-factant. On the basis of the analysis
of the elimina-tion products, it was confirmed that the main degra-dation process was the elimination of a β-hydrogen atom.
This mechanism is different from that of the pyrolysis gas chromatography, which will be dis-cussed elsewhere (S. Takano,
M. Kuzukawa, and M. Yamanaka, in preparation). 相似文献
3.
A. Fuangswasdi A. Charoensaeng D. A. Sabatini J. F. Scamehorn E. J. Acosta K. Osathaphan S. Khaodhiar 《Journal of surfactants and detergents》2006,9(1):21-28
This research reports on the adsorption and precipitation of mixtures of anionic and cationic surfactants having single and
twin head groups. The surfactant mixtures investigated were: (i) a single-head anionic surfactant, sodium dodecyl sulfate
(SDS), in a mixture with the twin-head cationic surfactant pentamethyl-octadecyl-1,3-propane diammonium dichloride (PODD)—adsorption
was studied on negatively charged silica; and (ii) a twin-head anionic surfactant, sodium hexadecyl-diphenyloxide disulfonate
(SHDPDS), and the single-head cationic surfactant dodecylpyridinium chloride (DPCI)—adsorption was studied on positively charged
alumina. Whereas the mixed surfactant system of SHDPDS/DPCI showed adsorption on alumina that was comparable to the of SHDPDS
alone, the mixed surfactant system of SDS/PODD showed increased adsorption on silica as compared with PODD alone. The adsorption
of the SDS/PODD mixture increased as the anionic and cationic system approached an equimolar ratio. Precipitation diagrams
for mixtures of single- and twin-head surfactant systems showed smaller precipitation areas than for single-head-only surfactant
mixtures. Thus, the combination of single- and double-head surfactants helps reduce the precipitation region and can increase
the adsorption levels, although the magnitude of the effect is a function of the specific surfactants used. 相似文献
4.
Formulating middle-phase microemulsions using mixed anionic and cationic surfactant systems 总被引:1,自引:0,他引:1
Although mixtures of anionic and cationic surfactants can show great synergism, their potential to precipitate and form liquid
crystals has limited their use. Previous studies have shown that alcohol addition can prevent liquid crystal formation, thereby
allowing formation of middle-phase microemulsions with mixed anionic-cationic systems. This research investigates the role
of surfactant selection in designing alcohol-free anionic-cationic microemulsions. Microemulsion phase behavior was studied
for three anionic-cationic surfactant systems and three oils of widely varying hydrophobicity [trichloroethylene (TCE), hexane,
and n-hexadecane]. Consistent with our hypothesis, using a branched surfactant and surfactants with varying tail length allowed
us to form alcohol-free middle-phase microemulsion using mixed anionic-cationic systems (i.e., liquid crystals did not form).
The anionic to cationic molar ratio required to form middle-phase microemulsions approached 1∶1 for univalent surfactants
as oil hydrophobicity increased (i.e., TCE to hexane to n-hexadecane); even for these equimolar systems, liquid crystal formation was avoided. To test the use of these anionic-cationic
surfactant mixtures in surfactant-enhanced subsurface remediation, we performed soil column studies: Greater than 95% of the
oil was extracted in 2.5 pore volumes using an anionic-rich surfactant system. By contrast, cationic-rich systems performed
very poorly (<1% oil removal), reflecting significant losses of the cationic-rich surfactant system in the porous media. The
results thus suggest that, when properly designed, anionic-rich mixtures of anionic and cationic surfactants can be efficient
for environmental remediation. By corollary, other industrial applications and consumer products should also find these mixtures
advantageous. 相似文献
5.
Donyaporn Panswad David A. Sabatini Sutha Khaodhiar 《Journal of surfactants and detergents》2011,14(4):577-583
Surfactant-modified mineral surfaces can provide both a hydrophobic coating for adsorbing organic contaminants and, in the
case of ionic surfactants, a charged exterior for adsorbing oppositely charged species. This research evaluates the precipitation
phase boundaries and synergistic behavior of the mixtures of carboxylate-based anionic extended surfactants with a pyridinium-based
cationic surfactant. One cationic surfactant (cetylpyridinium chloride) and four anionic extended surfactants were studied.
The anionic surfactants studied were ethoxy carboxylate extended surfactants with average carbon chain lengths of either 16
and 17 or 16 and 18 with 4 mol of a propylene oxide group and a different number of moles of an ethylene oxide group (2 and
5 mol). Precipitation phase boundaries of mixed anionic extended surfactants and cationic surfactant were evaluated to ensure
that the surface tension studies are in regions without precipitate. Surface tension measurements were conducted to evaluate
the critical micelle concentration of individual and mixed surfactant systems. Precipitation phase boundaries of these novel
mixed surfactant systems showed greatly reduced precipitation areas as compared to a conventional mixed surfactant system
which is attributed to the presence of the ethylene oxide and propylene oxide groups and resulting steric hindrances to precipitation.
Moreover, it was demonstrated that the CMC of mixed surfactant systems were much lower than that of individual surfactant
systems. Synergism was evaluated in the four systems studied by the β parameter which found that all systems studied exhibited
synergism. From these results, these novel mixed surfactant systems can greatly increase formulation space (reduce the precipitation
region) while maintaining synergism, although slightly reduced from conventional anionic-cationic mixtures reported previously. 相似文献
6.
K. H. Ott W. Wagner-Redeker W. Winkle 《European Journal of Lipid Science and Technology》1987,89(5):208-213
On-line Thermospray-LC-MS of Nonionic Surfactants Nonionic surfactants are often homologues with different degrees of ethoxylation. In addition, many products contain mixtures of nonionic surfactants, which differ in their chemical nature (e.g. polyglycol ethers of fatty alcohols and nonylphenol, sorbitan esters, fatty acid alkanolamides). For the analysis of such complex mixtures efficient separation methods are necessary: Thin layer chromatography is frequently applied to determine the type of surfactant. However, problems arise in quantitative evaluation and in determination of the hydrocarbon chain-distribution. The applicability of gaschromatography is limited by the requirements of volatility and thermal stability. Liquid chromatography should be an appropriate method for quantification, provided chromatographic resolution is sufficient. However, the identification is difficult if a refractive index detector is used because in such complex mixtures overlapping peaks are to be expected. For these reasons a universal and specific detector is required. In this contribution it is shown that the mass spectrometer may be linked to a liquid chromatograph by means of a modern Thermospray-Interface. This technique may be favourably applied to the analysis of nonionic surfactants. 相似文献
7.
Suresh Chavda Pratap Bahadur Vinod K. Aswal 《Journal of surfactants and detergents》2011,14(3):353-362
The interaction between mixtures of nonionic surfactant polyethylene glycol p-(1,1,3,3-tetramethyl butyl)-phenyl ether and cationic gemini surfactants alkanediyl-α,ω-bis(dimethyldodecylammonium bromide)
(12-s-12, where s = 2, 4 and 6) was studied using surface tension and small-angle neutron scattering measurements. Marked interaction was observed
for the investigated surfactants mixtures which depend upon the hydrophobic spacer length of the gemini surfactant and also
on the fraction of nonionic surfactant in the mixed systems. The results are discussed in terms of interaction parameters
calculated according to the theory of regular solutions which uses the critical micelle concentration determined tensiometrically
to calculate the molecular interaction parameter and the mole fractions of the two components in the mixed micelles. A relatively
high negative molecular interaction parameter value (up to −3.40) obtained for mixtures of nonionic and cationic gemini surfactant
indicates a presence of strong attractive interaction in the mixed system that increases with the spacer length of the gemini
surfactant. Micellar parameters deduced from small-angle neutron scattering measurements also compliment the surface tension
results. 相似文献
8.
The unrecovered hydraulic fracturing fluid will invade the matrix and induce water blockage, creating formation damage and hindering the oil or gas production rate. First, the synergistic effect of cationic Gemini surfactant (MQAS) and nonionic fluorosurfactant (N-2821) mixtures on reducing the surface tension and wettability alteration was investigated in this paper. The critical micelle concentration (CMC) of the surfactant mixture is one or two orders of magnitude lower than that of N-2821 and MQAS, indicating that the MQAS/N-2821 mixtures exhibit an apparent synergistic effect in reducing surface tension. Moreover, the maximal contact angle of MQAS/N-2821 mixtures reached 83.55° at αN-2821 = 0.5, and the total surfactant concentration of 1 × 10−4 mol/L due to the adsorption of surfactant. The adsorption mechanism of surfactants on the surface of quartz sand was then examined. The adsorption kinetics is consistent with the pseudo-second-order model at different surfactant concentrations, while the Freundlich model is suitable for describing the adsorption behavior of surfactants on the sandstone surface. This finding indicates that surfactant adsorption is multilayered. The MQAS/N-2821 surfactant mixtures have excellent surfactant activity due to the relationship of the capillary pressure to the surface tension, pore radius, and contact angle; thus, the addition of surfactant mixtures can reduce the liquid saturation effectively. Furthermore, the sequential imbibition experiments indicate that MQAS/N-2821 mixtures alter the wettability of the core plug, which results from the adsorption of surfactants. Compared with brine water, the MQAS/N-2821 mixtures decreased the liquid saturation and increased the permeability recovery ratios of the core plug. 相似文献
9.
Dynamic surface tensions (γt)—measured by the maximum bubble pressure method—of some surfactants containing two hydrophilic (sulfonate) groups and two
or three hydrophobic groups in the molecule (“gemini surfactants”), and of their mixtures with a nonionic surfactant or an
amine oxide, have been measured at 25°C in 0.1 M NaCl. Linearity of the plots of surface pressure vs. square root of the surface
age indicated that the systems studied were all diffusion-controlled. For the individual surfactant systems, the apparent
diffusion coefficient decreases with an increase in the number of alkyl chains and the bulkiness of the surfactant molecules.
For the mixtures, when interaction between the two surfactants is weak, γt at short times (t<1s) is close to that of the component with the lower surface tension; at longer times, it is closer to
that of the component with the lower equilibrium surface tension. When interaction is strong, γt at short times is greater than that of either component. The molar ratio at which maximum effect on γt is observed depends upon the strength of the interactions between the two surfactants. 相似文献
10.
Automatic turbidimetric analysis has been shown to be a simple and accurate method to determine the actives in anionic surfactants
as well as the actives in amine oxides. This technique has been applied to dilute solutions of these surfactants in the μM
range. Solutions containing mixtures of anionic surfactants and amine oxides can be positively resolved by turbidimetric titration
without interferences. Performing two titrations at different pH values ensures that the amine oxide is completely in its
nonionic form or totally protonated and behaving as a cationic surfactant. 相似文献
11.
A. Upadhyaya E. J. Acosta J. F. Scamehorn D. A. Sabatini 《Journal of surfactants and detergents》2007,10(4):269-277
This research evaluates the adsorption of anionic and cationic surfactant mixtures on charged metal oxide surfaces (i.e.,
alumina and silica). For an anionic-rich surfactant mixture below the CMC, the adsorption of anionic surfactant was found
to substantially increase with the addition of low mole fractions of cationic surfactant. Two anionic surfactants (sodium
dodecyl sulfate and sodium dihexyl sulfosuccinate) and two cationic surfactants (dodecyl pyridinium chloride and benzethonium
chloride) were studied to evaluate the effect of surfactant tail branching. While cationic surfactants were observed to co-adsorb
with anionic surfactants onto positively charged surfaces, the plateau level of anionic surfactant adsorption (i.e., at or
above the CMC) did not change significantly for anionic–cationic surfactant mixtures. At the same time, the adsorption of
anionic surfactants onto alumina was dramatically reduced when present in cationic-rich micelles and the adsorption of cationic
surfactants on silica was substantially reduced in the presence of anionic-rich micelles. This demonstrates that mixed micelle
formation can effectively reduce the activity of the highly adsorbing surfactant and thus inhibit the adsorption of the surfactant,
especially when the highly adsorbing surfactant is present at a low mole fraction in the mixed surfactant system. Thus surfactant
adsorption can be either enhanced or inhibited using mixed anionic–cationic surfactant systems by varying the concentration
and composition.
相似文献
D. A. SabatiniEmail: |
12.
Mixed micelles of some anionic-anionic, cationic-cationic, and ionic-nonionic surfactants in aqueous media 总被引:1,自引:0,他引:1
Sambhav Vora Alex George Hemangi Desai Pratap Bahadur 《Journal of surfactants and detergents》1999,2(2):213-221
Critical micelle concentrations (CMC) were obtained from tensiometric studies on several binary surfactant mixtures (anionic-anionic,
cationic-cationic, anionic-nonionic, and cationic-nonionic) in water at different mole fractions (0–1). The composition of
mixed micelles and the interaction parameter β, evaluated from the CMC data for different systems using Rubingh's theory,
are discussed. Marked interaction is observed for ionic-nonionic systems, whereas it is weak in the case of similarly charged
surfactants. The influence of counterion valence in the formation of mixed micelles was investigated, and results suggest
that in similarly charged surfactant mixtures, the degree of counterion binding does have a major role in deciding the extent
of interactions. Salt addition reveals a weakening of interactions in ionic-nonionic systems, and this is attributed to head
group charge neutralization and dehydration of the ethylene oxide units of the nonionic surfactants. Cloud point and viscosity
data on these systems support the observation. 相似文献
13.
Atmospheric-pressure ionization mass-spectrometric analysis of new anionic surfactants: The alkylpolyglucoside esters 总被引:1,自引:0,他引:1
Roberto Maffei Facino Marina Carini Gabriele Depta Paolo Bernardi Bruno Casetta 《Journal of the American Oil Chemists' Society》1995,72(1):1-9
Atmospheric-pressure ionization mass spectrometry has been successfully applied to characterization of a new class of anionic
surfactants, the alkylpolyglucoside esters of sulfosuccinic, citric and tartaric acid. Complex mixtures of final and intermediate
products were injected directly into the ion source without prior chromatographic separation. The constituents were identified
on the basis of quasi-molecular ions: cationized ions or solute-solute cluster ions in positive-ion mode, and deprotonated
ions in negative-ion mode. The mass-spectrometric data show that all three final products contain one nonionic and two different
types of anionic surfactants. The “real time,” highly sensitive mass-spectrometric approach proposed here is well suited for
quality control testing of tensides, to ensure the safety of the final product, and for the validation of the manufacturing
process, because it is able to identify the individual components of the mixture. 相似文献
14.
Measurements of the surface tension of aqueous solution of mixtures of sodium dodecyl sulfate (SDDS) with methanol and ethanol
in SDDS concentration range from 10−5 to 10−2 M and mixtures of sodium hexadecyl sulfonate (SHS) with methanol and ethanol at SHS concentration from 10−5 to 8 × 10−4 M and for methanol and ethanol from 0 to 21.1 and, 11.97 M, respectively, were carried out at 293 K. Moreover, the surface
tension of aqueous solution mixtures of SDDS with propanol in the concentration range from 0 to 6.67 M taken from the literature
was also considered. The results obtained indicate that it is possible to describe the relationship between the surface tension
and molar concentration or molar fraction of alcohol by Szyszkowski and Connors equations. However, the Fainerman and Miller
equation allows us to predict the isotherm of the surfactant tension at constant anionic surfactants concentration at which
their molecules are present in the solution in the monomeric form if the molar area of surfactants and alcohols can be determined.
Based on the surface tension isotherms, the Gibbs surface excess of anionic surfactants and alcohols concentration at water–air
interface was determined and then recalculated for Guggenheim-Adam surface excess concentration of these substrates, and next
the molar fraction of alcohols and surfactants in the surface layer was determined. These molar fractions were discussed with
regard to surfactant and alcohol standard free energy of adsorption at the water–air interface determined from Langmuir and
Aronson and Rosen equations. The standard free energy of adsorption determined in these ways was compared to that deduced
on the basis of pC20 and Lifshitz van der Waals-components of the anionic surfactant and alcohol tails. 相似文献
15.
R. Denig 《European Journal of Lipid Science and Technology》1974,76(9):412-416
Investigation of Surfactants by Pyrolysis-Gas-Chromatography A method for the routine analysis of surfactants using pyrolysis-gas-chromatography has been developed. This method is based on acid catalyzed degradation of nonionic and anion-active surfactants in Curie point pyrolyzer at 500°C and on base catalyzed degradation of cation-active compounds at 300°C, both followed by gas chromatography of the fragments formed. Aim of the investigations is not only the qualitative identification of the type of surfactant but also a quantitative statement on the composition of such products. 相似文献
16.
The HLD-NAC model has been used as an “equation of state” to predict the properties of microemulsion (μE) systems formulated
with either anionic or nonionic surfactants. The model uses the concept of the hydrophilic-lipophilic difference (HLD) to
calculate the chemical potential difference of transferring a surfactant from the oil to the aqueous phase; as a function
of formulation variables such as type of surfactant, oil, temperature, electrolyte concentration. The value of HLD is used
as a scaling parameter to calculate the net and average curvatures (NAC) of the surfactant at the water/oil interface. These
curvatures determine the phase volumes, phase transitions, and solubilization capacity of μEs. In this work, the HLD-NAC model
is extended to nonideal surfactant mixtures of anionic and nonionic surfactants. The phase behavior of limonene μEs formulated
with binary mixtures of sodium dihexyl sulfosuccinate with nonionic nonylphenol ethoxylates and alcohol ethoxylates was used
to determine the deviations of the HLD from the ideal mixing behavior. The deviations were fitted using a 2-parameters Margules
equation. The results suggests that the deviations in anionic-rich systems are due to the charge shielding effect of nonionic
surfactants, and in nonionic-rich systems, the deviations seem to be explained by the increase in hydration of the surfactant
headgroups due to the presence of anionic surfactants. When these corrections were used to predict the curvature of dioctyl
sulfosuccinate-dodecyl pentaethylene glycol-heptane μEs, the HLD-NAC model corrected for the nonidealities reproduced not
only the trends but also the actual range of values reported in the literature.
相似文献
Edgar J. AcostaEmail: |
17.
Experimental Study on Foam Properties of Mixed Systems of Silicone and Hydrocarbon Surfactants
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Youjie Sheng Xiujuan Wu Shouxiang Lu Changhai Li 《Journal of surfactants and detergents》2016,19(4):823-831
Silicone surfactants are inevitably involved in industrial applications in combination with hydrocarbon surfactants, but properties of the mixtures of silicone and hydrocarbon surfactants have received little attention, especially foam properties of the mixtures. In this study, aqueous solutions of respective binary mixtures of a nonionic silicone surfactant with anionic, cationic, and nonionic hydrocarbon surfactants were prepared for evaluation of their foam properties. Surface tension of aqueous solutions of the mixtures were measured with the maximum bubble pressure method. Foaming ability and foam stability of the mixtures were then evaluated with the standard Ross–Miles method. The findings show that the addition of the silicone surfactant results in a decrease in surface tension for aqueous solutions of the hydrocarbon surfactants. The critical micelle concentration (CMC) of the hydrocarbon surfactants is also changed by the additive silicone surfactant. Additionally, clear foam synergistic effects were observed in the mixtures of silicone and hydrocarbon surfactants, regardless of the ionic types of the hydrocarbon surfactant. The foam stability of the hydrocarbon surfactant was shown to generally improve with the increasing concentration of the silicone surfactant. Even so, aqueous solutions of different ionic hydrocarbon surfactants in the presence of the silicone surfactant will give different foam stabilities. The results of the present study are meant to provide guidance for the practical application of foams generated by the mixtures of the silicone and hydrocarbon surfactants. 相似文献
18.
Zheng-gang Cui Hong-xing Song Jun-jie Yu Jian-zhong Jiang Feng Wang 《Journal of surfactants and detergents》2011,14(3):317-324
Alkali-surfactant-polymer (ASP) flooding has been considered to be one of the useful tertiary oil recovery techniques. However,
field tests in China have revealed that serious side effects may occur due to using alkali. Thus alkali-free SP flooding is
more favorable in China. Unfortunately, surfactants effective in ASP flooding are usually ineffective in the absence of alkali
and new surfactants need to be designed. In this paper N-(3-Oxapropanoxyl)dodecanamide as a pure compound and a mixture of homologues with narrow EO number distribution, synthesized
by the reaction of lauroyl chloride with diglycolamine and addition of one ethylene oxide to coconut monoethanolamide respectively,
are examined for their adaptability in SP flooding. It is found that, when mixed with betaines, both products can reduce Daqing
crude oil/connate water interfacial tension to a magnitude of 10−3–10−4 mNm−1 at 45 °C in a wide surfactant concentration range, 0.01–0.5 wt%, and oil displacement tests using natural cores indicates
that a tertiary oil recovery of 18.6 ± 0.4% OOIP can be achieved by SP flooding with the N-(3-Oxapropanoxyl)dodecanamide as the main surfactant without adding any alkaline agent and neutral electrolyte. N-(3-Oxapropanoxyl)dodecanamide, as a nonionic surfactant without a cloud point and producible industrially from renewable
materials, is an ideal surfactant for SP flooding in the absence of an alkaline agent. 相似文献
19.
The Characteristic Curvature of Ionic Surfactants 总被引:1,自引:1,他引:0
Edgar J. Acosta Jessica Sh. Yuan Arti Sh. Bhakta 《Journal of surfactants and detergents》2008,11(2):145-158
Characterizing the hydrophilic-lipophilic nature of a surfactant molecule has been a challenge for colloid scientists and
technologists. The hydrophilic-lipophilic balance (HLB), the packing factor, the phase inversion temperature (PIT) and the
natural curvature of the surfactant are all terms that seek to address this issue. In this article we build on the hydrophilic–lipophilic
difference concept (HLD) (Salager et al. Langmuir, 16, 5534–5539, 2000) to develop a methodology to determine a characteristic
curvature (Cc) for ionic surfactants based on the phase behavior of mixed ionic surfactant microemulsions. In essence, the
method consists of evaluating the shift in optimal electrolyte concentration as a function of the mole fraction of the test
surfactant in a mixture with a reference surfactant, sodium dihexyl sulfosuccinate (SDHS) and applying the appropriate HLD
equation for ionic surfactant mixtures to determine Cc. The values of Cc were determined for a range of surfactants, including
sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), sodium naphthenate, and others. The method was also
extrapolated to nonionic additives and hydrophilic linkers. It was observed that the calculated values of Cc were similar
to those predicted by group contribution models, however the proposed method can be used even for complex surfactant mixtures.
Finally, when Cc values were compared to apparent packing factor and HLB values, it was found that Cc is correlated with the
apparent packing factor of ionic surfactants, and that Cc correlates with the HLB value for nonionic amphiphiles. The physical
interpretation of Cc, and its potential application in the Net-Average Curvature equation of state for oil-surfactant-water
systems is discussed.
相似文献
Edgar J. AcostaEmail: |
20.
Measurements of the surface tension (γ
LV
) and the advancing contact angle (θ) on poly(tetrafluoroethylene) (PTFE) were carried out for aqueous solutions of sodium decyl sulfate (SDS) and sodium dodecyl
sulfate (SDDS) and their mixtures. The results obtained indicate that the values of the surface tension and the contact angle
of solutions of surfactants on PTFE surface depend on the concentration and composition of the surfactants mixture. On the
curves presenting the relationship between the surface tension, contact angle and monomer mole fraction of SDDS (α) in the mixture of SDDS and SDS, there is a minimum at α equal to 0.8 which together with the negative values of the interaction parameters indicate that synergism occurs in surface
tension and contact angle reduction almost in the range of concentration corresponding to the saturated monolayer of surfactants
at the water–air interface. The results and calculations obtained also indicate that for single surfactants and their mixtures
at a given concentration in the bulk phase, the values of surface excess concentration of the surfactants at water–air and
PTFE–water interfaces are nearly the same, which suggests that the orientation of SDDS and SDS molecules at both interfaces
in saturated monolayer should be vertical to the interfaces. Taking into account the values of the monomer mole fractions
of the surfactants in a mixed monolayer at the water–air interface and values of the contact angle of a single surfactant
on the PTFE surface, it is possible in a simple way to predict the values of the contact angle of a mixture at a given concentration
and composition. 相似文献