SILOXANE-TRIAZOLEGLUCOSIDE AND GLUCOSIDE SURFACTANT FORMULATIONS FOR FIRE-FIGHTING FOAM APPLICATIONS

Abstract

The compound below may be used in a fire-fighting formulation along with a poly(glucoside)-alkane, a poly(ethylene glycol) monoalkyl ether, and water. The value n is 2 or 3, R is a C3-C9 alkylene group, X is O or N(COCH.sub.3), and c is a positive integer. It may be made by reacting a polysaccharide with acetic anhydride, propargyl alcohol, and an azidoalkyltris(trimethylsiloxy)silane or an azidoalkylbis(trimethylsiloxy)methylsilane. Alternatively, it may be made by reacting a polysaccharide with propargylamine, acetic anhydride, and an azidoalkyltris(trimethylsiloxy)silane or an azidoalkylbis(trimethylsiloxy)methylsilane.

##STR00001##

Claims

1. A compound having the formula: ##STR00007## wherein n is 2 or 3; wherein R is a C3-C9 alkylene group; wherein X is O or N(COCH.sub.3); and wherein c is a positive integer.

2. The compound of claim 1, wherein the compound is ##STR00008##

3. The compound of claim 1, wherein the compound is ##STR00009##

4. The compound of claim 1, wherein the compound is ##STR00010##

5. A composition comprising: the compound of claim 1; a poly(glucoside)-alkane having the formula: ##STR00011## wherein n is an integer from 1 to 20; and wherein x is a positive integer; and water.

6. The composition of claim 5, further comprising: a poly(ethylene glycol) monoalkyl ether having the formula: ##STR00012## wherein z is a positive integer; and wherein p is a positive integer.

7. A method comprising: mixing the composition of claim 5 with air to form a foam.

8. The method of claim 7, further comprising: applying the foam to a fire.

9. The method of claim 7, further comprising: applying the foam to a fire in an amount sufficient to extinguish the fire.

10. A method comprising: providing a polysaccharide having the formula: ##STR00013## wherein c is a positive integer; reacting the polysaccharide with acetic anhydride to form acetate groups, forming a polysaccharide acetate having the formula: ##STR00014## reacting the polysaccharide acetate with propargyl alcohol to form a propargyl compound having the formula: ##STR00015## and reacting the propargyl compound with an azidoalkyltris(trimethylsiloxy)silane or an azidoalkylbis(trimethylsiloxy)methylsilane to form a compound having the formula: ##STR00016## wherein n is 2 or 3; and wherein R is a C3-C9 alkylene group.

11. The method of claim 10, wherein the polysaccharide is maltose.

12. The method of claim 10, wherein the azidoalkyltris(trimethylsiloxy)silane is 3-azidopropyltris(trimethylsiloxy) silane.

13. The method of claim 10, wherein the azidoalkylbis(trimethylsiloxy)methylsilane is 3-azidopropylbis (trimethylsiloxy)methylsilane.

14. A method comprising: providing a polysaccharide having the formula: ##STR00017## wherein c is a positive integer; reacting the polysaccharide with propargylamine to form a propargyl compound having the formula: ##STR00018## reacting the propargyl compound with acetic anhydride to form acetate groups, forming a polysaccharide acetate having the formula: ##STR00019## and reacting the polysaccharide acetate with an azidoalkyltris(trimethylsiloxy)silane or an azidoalkylbis(trimethylsiloxy)methylsilane to form a compound having the formula: ##STR00020## wherein n is 2 or 3; and wherein R is a C3-C9 alkylene group.

15. The method of claim 14, wherein the polysaccharide is maltose.

16. The method of claim 14, wherein the azidoalkyltris(trimethylsiloxy)silane is 3-azidopropyltris(trimethylsiloxy)silane.

17. The method of claim 14, wherein the azidoalkylbis(trimethylsiloxy)methylsilane is 3-azidopropylbis(trimethylsiloxy)methylsilane.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0012] A more complete appreciation will be readily obtained by reference to the following Description of the Example Embodiments and the accompanying drawings.

[0013] FIG. 1 shows a chemical synthesis of tetrasiloxane-triazolediglucoside surfactant (MD2102-134).

[0014] FIG. 2 shows H.sup.1 NMR spectra for tetrasiloxane-triazolediglucoside.

[0015] FIG. 3 shows C.sup.13 NMR spectra for tetrasiloxane-triazolediglucoside.

[0016] FIG. 4 shows Si.sup.29 NMR spectra for tetrasiloxane-triazolediglucoside.

[0017] FIG. 5 shows a chemical synthesis of tetrasiloxane-triazolecarbonyldiglucoside surfactant (MD2102-142).

[0018] FIG. 6 shows H.sup.1 NMR spectra for tetrasiloxane-triazolecarbonyldiglucoside.

[0019] FIG. 7 shows C.sup.13 NMR spectra for tetrasiloxane-triazolecarbonyldiglucoside.

[0020] FIG. 8 shows a chemical synthesis of trisiloxane-triazolecarbonyldiglucoside surfactant (MD2102-172).

[0021] FIG. 9 shows H.sup.1 NMR spectra for trisiloxane-triazolecarbonyldiglucoside.

[0022] FIG. 10 shows C.sup.13 NMR spectra for trisiloxane-triazolecarbonyldiglucoside.

[0023] FIG. 11 shows surface tension versus total surfactant (siloxane-triazoleglucoside+alkylpolyglucoside) concentration with fitted lines to determine CMC values.

[0024] FIG. 12 shows change in foam layer thickness (initial thickness 4 cm) with time when placed on a hot heptane pool due to fuel induced foam degradation.

[0025] FIG. 13 shows change in foam layer thickness (initial thickness 4 cm) with time when placed on a hot heptane pool due to fuel induced foam degradation.

[0026] FIG. 14 shows heptane vapor permeation through a foam layer (4-cm initial thickness) placed on hot (60 C.) heptane pool with time.

[0027] FIGS. 15A-B show gasoline fire extinction times versus foam application rate onto the edge of a 19-cm diameter gasoline pool fire for the 3-component siloxane-triazoleglucoside formulations (inverted triangles, diamonds, and squares), zwitterionic siloxane formulation (stars), RefAFFF (circles), and non-ionic siloxane-polyoxyethylene (502W-Glucopon225DK, squares) surfactant formulation with compositions shown in Table 1. FIG. 15A shows time for complete fire extinction and FIG. 15B shows time for extinction of 90% of the pool surface.

[0028] FIGS. 16A-B show gasoline fire performances. FIG. 16A shows pool coverage time versus foam application rate onto the edge of a 19-cm diameter gasoline pool fire for the siloxane-triazoleglucoside formulations, zwitterionic siloxane formulation, RefAFFF, and non-ionic siloxane-polyoxyethylene (502W-Glucopon225DK, triangles) surfactant formulation with compositions shown in Table 1. FIG. 16B shows expansion ratio versus foam flow rates.

[0029] FIGS. 17A-B show heptane fire performances of extinction time vs foam flow rate listed in Table 1 (FIG. 17A) and 90% extinction time vs foam flow rate (FIG. 17B).

[0030] FIG. 18 shows heptane pool-fire coverage time vs foam flow rate for formulations listed in Table 1.

DETAILED DESCRIPTION

[0031] In the following description, for purposes of explanation and not limitation, specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that the present subject matter may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known methods and devices are omitted so as to not obscure the present disclosure with unnecessary detail.

[0032] Disclosed herein are fluorine-free surfactant formulations to generate foams that have high fire suppression comparable to that of the firefighting foam used currently, worldwide, Aqueous Film Forming Foam (AFFF), which contains fluorocarbon surfactants with significant environmental impact. The formulations include custom synthesized tetrasiloxane-triazolediglucoside (MD2102-134), trisiloxane-triazolecarbonyldiglucoside (MD2102-172), and tetrasiloxane-triazolecarbonyldiglucoside (MD2101-142) surfactants that exhibit synergism with alkylglycoside surfactants and result in high fire suppression for gasoline and jet fuel fires. The 3% concentrate of the surfactant solutions have low viscosity and are suitable as candidates for drop-in replacement for AFFFs unlike many commercial fluorine-free formulations. As an example, a surfactant formulation composed of trisiloxane-triazolediglucoside (MD2102-134)) and alkyl polyglucoside surfactants and other components is shown to spread extremely quickly, suppress the fuel vapors, and extinguish a gasoline and jet fuel pool fires closer to the values measured for AFFF. Described herein are MD2102-134, MD2102-172, and MD2102-142 surfactant structural features, synthesis routes, formulation compositions' effect on the foam's resistance to the fuel vapors emerging from the pool surface that correlate with fire suppression effectiveness. The structural features include a range of head and tail dimensions. Compositions include the range of relative amounts of siloxane to hydrocarbon surfactants to achieve synergistic extinction and increased foam spreading on the pool surface. Fuel vapor resistance is quantified by the ranges of fuel/heat induced foam degradation and fuel vapor permeation rate relative to AFFF. Surface and near zero interfacial tensions show tendency for emulsification with fuel that might have led to surface cooling and lowering of fuel vapor pressure, which might have helped to quickly suppress small flamelets that tend to prolong complete fire extinction.

[0033] Disclosed herein are three non-ionic tetrasiloxane and trisiloxane surfactants that have comparable fire suppression to the zwitterionic-siloxane formulation (US Patent Publication No. US2022/11420083 B2, Pub. Date Aug. 23, 2022). The non-ionic surfactants are less susceptible to ions in sea water, which may be used for firefighting on ships. The foams generated from the non-ionic siloxane formulations were found to spread quickly on a burning gasoline pool surface similar to the prior zwitterionic-siloxane formulation. The present formulation contains a glycoside and a solvent along with nonionic-tetrasiloxane or trisiloxane surfactants. The superior fire suppression effectiveness is due to increased oleophobicity of the tail that blocks the fuel vapor permeation through foam covering the pool surface while maintaining amphiphilicity with a non-ionic head group. Also significant is the synergistic interaction with hydrocarbon co-surfactant, where the fire extinction times are smaller for the combination of the surfactants compared to those for the two surfactants individually. The synergism blocks the fuel permeation and contributes to faster extinction without using excess solution. The present formulation also has low viscosity for the 3% concentrate, which makes it suitable as a drop-in replacement to AFFF unlike many commercial fluorine-free foams.

[0034] The present formulations include compound 1. Compound 1 has two isomers varying in where the carbon atom bonds to the triazole ring, at either the 4 (1a) or 5 (1b) position. Three specific compounds, which may include both isomers, are MD2102-134 (tetrasiloxane-triazolediglucoside 9), MD2102-172 (trisiloxane-triazolecarbonyldiglucoside, 10), and MD2102-142 (tetrasiloxane-triazolecarbonyldiglucoside 11). The syntheses of these compounds are described herein and may be generalized to any polysaccharide 2, azidoalkyltris(trimethylsiloxy) silane, or azidoalkylbis(trimethylsiloxy)methylsilane.

##STR00005##

[0035] A fire-fighting formulation is made by combining 1 with poly(glucoside)-alkane 12, optionally poly(ethylene glycol) monoalkyl ether 13, and water. In 12, n is an integer from 1 to 20 and x is a positive integer. In 13, z and p are positive integers. A foam is made by mixing the formulation with air, and the foam may be applied to a fire to extinguish it. Though not limited to such amounts, example percentages of the ingredients are disclosed herein, and the formulation may be made with any amounts that result in a fire-fighting foam.

##STR00006##

[0036] When a member of each surfactant class 1 and 12 with certain characteristics is combined in a foam generating formulation, the foam produced displays an effective fire suppression capability. It may or may not also include a diethyleneglycol butylether (DGBE) solvent 13 where parameters p and z are greater than or equal to 1. Table 1 shows an example formulation. The ratio of the siloxane to glycoside surfactants may range from 0.03 to 5.

TABLE-US-00001 TABLE 1 Fluorine-free and RefAFFF formulations Siloxane- Nonionic triazoleglucoside Zwitterionic trisiloxane- (MD2102-134, tetrasiloxanebetaine polyoxyethylene MD2102-142, or (MD2062-54)) 502W RefAFFF MD2102-172) formulation.sup.1 formulation.sup.2 formulation.sup.3 0.28 to 0.15% 0.065% Zwitterionic 0.2% Trisiloxane 0.3% Siloxane- tetrasiloxane surfactant, Capstone triazoleglucoside surfactant e.g., Dowsil 502W 1157 tetrasiloxane- additive sulfobetaine 0.42 to 0.22% 0.3% Hydrocarbon 0.3% 0.2% Hydrocarbon surfactant, e.g., Hydrocarbon Glucopon215 surfactant, e.g., Glucopon225DK surfactant, CS UP Glucopon225DK Glucopon225DK 0.5% solvent, 0.5% solvent, e.g., 0.5% solvent, 0.5% DGBE e.g., DGBE DGBE DGBE 99% Distilled 99.135% Distilled 99% Distilled 99% water water water Distilled water .sup.1U.S. Pat. No. 11,420,083 (Aug. 23, 2022) .sup.2U.S. Pat. No. 11,117,008 (Sep. 14, 2021), Colloids and Surfaces A, 579, 123686, 2019 .sup.3RefAFFF passed the 28 ft.sup.2 US Mil-F-24385F fire test with an extinction time of 26 s, burnback time of 562 s, 25% liquid drainage time of 317 s, foam expansion ratio of 7.5 (Journal of Surfactants and Detergents, 21, 711-722, 2018)

[0037] These materials advance the development of non-ionic formulations of fluorine-free surfactants for generation of foams with fuel vapor blocking property and fire suppression activity that approaches the fire extinction performance level of fluorocarbon surfactant containing AFFF formulations for gasoline fires. Both the two-step synthesis of the siloxane-triazoleglucoside surfactants and fire suppression performance using the formulations show comparable performance with AFFF. Furthermore, trisiloxane-triazolecarbonyldiglucoside (MD2102-172) has a foam degradation rate comparable to that of AFFF when the foam is placed on warm gasoline unlike many fluorine-free foams. Previously, a similar result for zwitterionic tetrasiloxane-sulfobetaine was reported. The sulfobetaine head tends to self-destruct the tetrasiloxane tail (Sulfobetaine-siloxanes: A class of self-destructive surfactants, Journal of Surfactants and Detergents, Submitted) unlike the present non-ionic surfactant formulations. Also, the non-ionic formulations are less susceptible to interference from ions present in salt water applications on ship board firefighting. Previously, a similar result for heptane fires was reported using a formulation containing a commercially available siloxane surfactant. But, the gasoline fires are significantly more difficult to suppress than the heptane fires partly due to gasoline's higher volatility and ability to extract surfactant from the foams causing bubble coalescence and higher fuel transport through a foam layer covering the pool surface. The 3% concentrate of the current invention is a potential drop-in replacement for AFFF. Very few commercial foams have low viscosity for a 3% concentrate unlike the present formulation and therefore most commercial formulations would require very expensive hardware modifications and are not suitable drop-in replacements for AFFF. The fluorine-free feature is critical for environmental regulation compliance. A methodology is developed where the fuel resistance property measurements are used as metrics to quantitatively rank numerous commercial formulations that enable identification of superior performing fluorine-free surfactant relative to AFFF. In addition, near zero interfacial tension of the siloxane-triazolediglucoside formulations may enable formation of fine emulsion containing small aqueous droplets at the fuel pool surface and induce more effective cooling of the hot pool reducing vapor pressure. This could also explain the observation of reduced edge flame (small flamelets) with the present formulations unlike the nonionic trisiloxane 502W formulation.

[0038] Siloxane-triazoleglucoside surfactant synthesisThe synthesis of MD2102-134 is shown in FIG. 1. The synthesis begins by complete acetylation of maltose by heating in a mixture of acetic anhydride using potassium acetate as the base. In this way, maltose octaacetate was prepared in good yield. Next, propargyl alcohol was reacted with the maltose octaacetate catalyzed by boron trifluoride diethyl etherate in dichloromethane solvent to give the glycosylation product 1-propargylmaltose heptaacetate. In the next step, the [3+2]cycloaddition reaction between 3-azidopropyltris(trimethylsiloxy)silane and 1-propargylmaltose heptaacetate was carried out by refluxing equimolar quantities in acetonitrile solvent in the presence of the catalysts triethylamine and copper (I) iodide. The product from the cycloaddition reaction was a 1,4-substituted-1,2,3-triazole linking the tetrasiloxane with the protected maltose. In the last step, the acetyl protecting groups on the maltose sugar were deprotected by reaction with excess diethylamine in methanol solvent. After evaporation of the solvent, the product from the last step in the synthesis was the surfactant MD2102-134. The NMR of MD2012-134 dissolved in methanol-d.sub.4 are shown in the FIGS. 2-4. The proton NMR spectrum shows the 1,2,3-triazole ring proton at 8.0 ppm and the maltose ring protons from 5.1-3.0 ppm. The methylene group (CH.sub.2) bonded to silicon resonates at 0.5 ppm and the tris(trimethylsiloxy) group shows a strong signal at 0.1 ppm. The carbon-13 spectrum shows that all of the acetate protecting groups that would have resonated at 170 ppm were no longer present. The carbon-13 spectrum also shows the 1,2,3-triazole ring carbons resonating at 144 and 124 ppm. The silicon-29 spectrum shows the trimethylsilyl groups (Me.sub.3Si) with a chemical shift of +8 ppm while the silicon atom bonded to the propane chain (CH.sub.2SiO.sub.3) had a chemical shift of 66 ppm.

[0039] The synthesis of MD2102-142 is shown in FIG. 5. In the first step, maltose was reacted with excess propargylamine at 50 C. to produce the 1-deoxy-1-propargylaminomaltose. Next, the 1-deoxy-1-propargylaminomaltose was reacted with acetic anhydride in methanol solvent to give the product N-acetyl-1-deoxy-1-propargylaminomaltose. In the last step, the [3+2]cycloaddition reaction between 3-azidopropyltris(trimethylsiloxy)silane and N-acetyl-1-deoxy-1-propargylaminomaltose was carried out by refluxing equimolar quantities in methanol solvent in the presence of the catalysts triethylamine and copper (I) iodide. The product from the last reaction step was the surfactant MD2102-142 which incorporated a 1,2,3-triazole linking the tetrasiloxane to the 1-deoxy-1-aminomaltose sugar. The NMR of MD2012-142 dissolved in methanol-d.sub.4 are shown in the FIGS. 6-7. The proton NMR spectrum shows the 1,2,3-triazole ring proton resonating at 7.8 ppm. The two singlets at 2.25 and 2.2 ppm are the methyl group of the acetyl substituent, which are two peaks owing to restricted rotation about the amide bond. The tris(trimethylsiloxy) group shows a strong singlet at 0.1 ppm. The carbon-13 spectrum shows the carbonyl signal at 172 ppm and the trimethylsiloxy groups as a strong singlet at 0.6 ppm.

[0040] The synthesis of MD2102-172 is shown in FIG. 8. The synthesis started from the intermediate N-acetyl-1-deoxy-1-propargylaminomaltose that had already been made in the synthesis of MD2102-142. Thus, equimolar amounts of N-acetyl-1-deoxy-1-propargylaminomaltose and 3-azidopropylbis(trimethylsiloxy)methylsilane were reacted in a [3+2]cycloaddition reaction using methanol as solvent and triethylamine and copper (I) iodide as catalysts. The product from the reaction was the surfactant MD2102-172 which incorporated a 1,2,3-triazole linking the trisiloxane to the 1-deoxy-1-aminomaltose sugar. The NMR of MD2012-172 dissolved in methanol-d.sub.4 and DMSO-d.sub.6 are shown in the FIGS. 9-10. The proton NMR spectrum shows the 1,2,3-triazole ring protons at 7.8 and 8.0 ppm, indicating there was a mixture of both 1,4- and 1,5-isomers. The maltose ring protons were found from 5.7-3.0 ppm. The two singlets at 2.1 and 1.9 ppm are the methyl group of the acetyl substituent, which are two peaks owing to restricted rotation about the amide bond. The two trimethylsiloxy groups were a singlet at 0.0 ppm and the other methyl group bonded to silicon resonated at 0.5 ppm. The carbon-13 spectrum shows the carbonyl signals at 172 ppm and the trimethylsiloxy groups as a strong singlet at 0.67 ppm and the other carbon attached to silicon at 1.47 ppm.

[0041] Measurements of surfactant propertiesThe surface and interfacial tensions as well as times for complete degradation of foams placed on alcohol-free gasoline at 37 C. and heptane at 60 C. are shown in Table 2. The surface and interfacial tensions are measured using DuNoy ring method. Methods used for foam degradation were described in detail in Colloids and Surfaces A, 579, 123686, 2019.

TABLE-US-00002 TABLE 2 Properties of siloxane-triazoleglucoside formulations from Table 1, column 1 MD2102- MD2102- MD2102- 134Form 172Form 142Form Surface tension 20.6 21.2 21.2 (mN/m) Interfacial tension 0.99 0.70 1.24 heptane (mN/m) Interfacial tension 0.25 0.26 0.28 gasoline (mN/m) Foam lifetime 46 6 130 20 1 gasoline at 37 C. (min) Foam lifetime 13.8 1 17 4 4 1 heptane at 60 C. (min) EDC value (heptane, 4.7 10.sup.4 2.0 10.sup.2 4.9 10.sup.4 cm.sup.2/s) 2.0 10.sup.4 0.1 10.sup.2 4.0 10.sup.4

[0042] Critical micelle concentrations (CMC) are measured from surface tension versus surfactant concentration in solution for individual siloxane-triazoleglucoside surfactants and for mixtures with alkylpolyglucoside shown in column 1 of Table 1. Two lines are fitted for each curve and CMC is determined as the value at the intersection of the two lines. The equations for the lines are displayed in FIG. 11. The CMC values are displayed in Table 3.

TABLE-US-00003 TABLE 3 CMC values for individual siloxane surfactants and siloxane formulations (column 1, table 1) Individual 2:3 Siloxane (Table 1) surfactant surfactant: Glucopon225DK CMC (wt %) Mixture CMC (wt %) MD2102-134 0.094 0.08-0.12 MD2102-142 0.031 0.064 MD2102-172 0.065 0.083

[0043] MD2102-134 surfactant on its own formed an opaque suspended solution that did not foam well, turned more clear upon G225 and DGBE addition. -142 went easily into solution with some stirring, formed slightly hazy brown solution that foamed okay. -172surfactant on its own formed an opaque suspension that foamed well, solution turned clear upon G225 and DGBE addition. The -134:G225 mixture CMC profile had a very small sloped region making CMC determination challenging. The use of one point in the sloped versus linear region and vice versa produced a possible CMC range between 0.08 and 0.12 wt %. The higher end was chosen for the 6 CMC calculation wanting to have more surfactant than less, just in case. Surfactants were evaluated in the following formulations: 0.28% MD2102-134, 0.42% G225, 0.5% DGBE; 0.15% MD2102-142,0.225% G225, 0.5% DGBE; and 0.2% MD2102-172, 0.3% G225, 0.5% DGBE.

[0044] A 4-cm thick foam layer placed on hot (60 C.) heptane pool degrades as the heptane vapor permeates through the foam. The change in foam layer thickness with time is shown in FIG. 12. It shows that MD2102-172Form has slower degradation than MD2102-134 and MD2102-142. FIG. 13 shows similar results when the 4-cm thick foam layer was placed on a warm gasoline pool. Indeed, MD2102-172 shows degradation rate similar to AFFF.

[0045] FIG. 14 shows heptane vapor permeation through the foam layer with time for a 4-cm (initial thickness) thick foam layer placed on hot (60 C.) heptane pool. Heptane concentration above the foam surface is measured using FTIR method as described in Colloids and Surfaces A, 522, 1-17, 2017. Heptane fuel flux for the 3 foam formulations are shown. All 3 showed poor foam stability over heptane specifically, leading to rapid holes in the foam layer and quick flux profiles. However, at short time scales, it can clearly be seen that all 3 block heptane fuel vapors well. No quantifiable differences in flux are noted from the profiles other than MD2102-172 seems to be more stable on heptane and produced a longer flux profile, but its early time profile is similar to MD2102-134 and -142 formulations.

[0046] Fuel transport was only collected for heptane. The raw fuel transport profiles in FIG. 14 were used with collected foam height data with time (collected during the fuel transport experiment) to derive an effective diffusion coefficient (EDC) by applying Fick's law. Fick's law was applied at any given time using the measured foam layer thickness instead of the initial foam layer thickness of 4-cm using a pseudo steady state approximation. The pseudo steady Fick's law model fitted to the fuel flux data are displayed in Table 2. The EDC values indicate the transport performance of the foams, independent of differences in foam degradation.

[0047] Foam generation and application for fire suppressionFoams can be generated using a device that mixes air and water at different ratios known as the expansion ratio (Ex, volume of foam/volume of liquid) and are described in Colloids and Surfaces A, 579, 123686, 2019. As an example, foams are generated by sparging air continuously at a constant rate through a porous disc while feeding solution continuously to maintain a constant liquid column height (3-cm) above the porous disc (25-50 m pores, 1.9-cm diameter) by using a leveling system. Foam collects to form 5.5-cm thick layer above the solution surface while flowing out from a 2.5-cm diameter outlet tube connected to the cap of a 0.7-liter plastic bottle (7.6-cm diameter, 15.9-cm height). Foam flow rate is maintained constant during fire extinction and are measured by recording time taken to collect 500 mL volume before and after fire extinction. Foam expansion ratio (volume of foam/weight of foam) is also measured before and after each fire extinction experiment in order to calculate liquid flow rate (foam flow rate/expansion ratio). To apply the foam continuously on to burning fuel pool, the outlet tube from the foam generating plastic bottle is placed about 1-inch above the pool surface. The foam is applied directly at the near-edge of a burning gasoline (alcohol-free) pool (circular shape) and allowed to spread across the pool to cover it and until fire extinction, or a maximum time of 5 minutes if there is no extinction. Extinction experiments are conducted at different values of liquid (or foam) flow rates. The gasoline pool is allowed to burn for 60 s (preburn time) prior to the foam application. The pool consisted of 1-cm thick fuel layer above a 5-cm thick water layer. The fuel level is maintained at 1-cm below the rim of the 19-cm diameter crystallizing dish to accommodate the foam and prevent overflow of the fuel by using a leveling system. The apparatus used for generating the foams and conducting fire extinction were developed previously by us [Journal of Surfactants and Detergents, 21, 711-722, 2018].

[0048] Gasoline fire extinction can be conducted by applying the foams from the foam generating device on to a burning liquid fuel pool at different application rates. Examples of such testing results are depicted in FIG. 15A where the extinction time is measured as a function of measured foam flow rates. For comparison, extinction results for the non-ionic trisiloxane and Ref AFFF formulations listed in Table 1 are shown in FIG. 15A. FIG. 15A demonstrates that the three nonionic siloxane-triazoleglucoside formulations shown in column 1 of Table 1 have fire suppression profiles comparable to the zwitterionic siloxane formulation (MD2062-54Form) and are significant improvements over the trisiloxane-polyoxyethylene-502W formulation and are close the extinction profile of RefAFFF. The extinction times for the non-ionic siloxane-triazole formulation are about 1.6 times that of RefAFFF. The MilSpec solution application rate of 2 gallons per minute for a 28 ft.sup.2 gasoline fire corresponds to 2.9 kg/min/m.sup.2, which corresponds to a solution flow rate of 82 mL/min and foam flow rate of 650 mL/min for the 19-cm diameter bench scale data shown in FIG. 15A. FIG. 15B shows 90% fire extinction profile for the three formulations listed in Table 1. The extinction time data were collected when 90% of the pool area was extinguished but small edge flames linger before complete fire extinction. The 90% extinction times are much closer to the complete extinction times displayed in FIG. 15A because of reduced edgeflames. Edgeflames are small flamelets that linger on the pool surface and prolong complete fire extinction despite fire being extinguished on most of the pool surface.

[0049] FIGS. 16A-B show foam coverage times of burning gasoline pool versus foam application rate for the present formulations and foam expansion ratio, which is the ratio of foam volume to liquid volume contained in the foam. The coverage times for the formulations shown in column 1 of Table 1 are comparable to the zwitterionic siloxane formulation (MD2062-054) and are quicker than RefAFFF and siloxane-polyoxyethylene502W formulation especially at low foam flow rates as shown in FIG. 16A. The foam expansion ratios for the formulations of this invention are slightly drier than the zwitterionic siloxane formulation as shown in FIG. 16B.

[0050] It is important to note that the fire suppression depends on fuel. It was shown previously that fluorine-free foams' fire suppression is affected by the type of fuel (gasoline versus heptane) more than AFFFs (NRL Memorandum Report NRL/MR/6123-19-9895). Synergism between two families of surfactants also depends on the fuel. FIGS. 17A-B and 18 show results for heptane fire. FIG. 17A shows that only MD2102-134 has extinction time profile comparable to the zwitterionic-siloxane formulation (MD2062-54). But both have extinction profiles inferior to the siloxane-polyoxyethylene502W formulation and the RefAFFF. FIG. 17B shows times for 90% extinction are comparable for both MD2102-134 and MD2102-172, while MD2102-142 deviates especially at low foam flow rates.

[0051] FIG. 18 shows coverage times for a heptane pool fire for all three present siloxane formulations are comparable to the zwitterionic-siloxane formulation (MD2062-54) and are quicker than the siloxane-polyoxyethylene502W formulation and RefAFFF.

[0052] Many modifications and variations are possible in light of the above teachings. It is therefore to be understood that the claimed subject matter may be practiced otherwise than as specifically described. Any reference to claim elements in the singular, e.g., using the articles a, an, the, or said is not construed as limiting the element to the singular.