An Introduction to Surfactants

237 Pages·2014·1.62 MB·English

by  Tharwat F. Tadros

DeGruyterGraduate
Tadros∙AnIntroductiontoSurfactants
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Tharwat F. Tadros
An Introduction to
Surfactants
|
Author
Prof.TharwatF.Tadros
89NashGroveLane
WokinghamRG404HE
Berkshire,UK
Email:[email protected]
ISBN978-3-11-031212-6
e-ISBN978-3-11-031213-3
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Preface
Surfactantsfindapplicationinalmosteverychemicalindustryofwhichthefollowing
maybeworthmentioning:detergents,paints,dyestuffs,cosmetics,pharmaceuticals,
agrochemicals,fibers,plastics,etc.Moreover,surfactantsplayamajorroleintheoil
industry,forexampleinenhancedandtertiaryoilrecovery.Theyarealsooccasionally
used for environmentalprotection,e.g. in oil slick dispersants.Therefore, a funda-
mentalunderstandingofthephysicalchemistryofsurfaceactiveagents,theirunusual
propertiesandtheirphasebehaviorisessentialformostindustrialchemists.Inaddi-
tion,anunderstandingofthebasicphenomenainvolvedintheapplicationofsurfac-
tants,suchasinthepreparationofemulsionsandsuspensionsandtheirsubsequent
stabilization,innanoemulsions,inmicroemulsions,inwettingspreadingandadhe-
sion,etc.,isofvitalimportanceinarrivingattherightcompositionandcontrolofthe
systeminvolvedThisbookhasbeenwrittenasanintroductiontograduatechemists,
industrialformulatorswhoareusingsurfactantsintheaboveapplications.Asfaras
possible,thebookiswritteninasimplewaywithouttoomuchdetailinordertoen-
ablethereadertomakeastartwiththebasicphysicalphenomenainvolvedinsucha
vastfield.Formoredetail,thereadercanrefertomorecomprehensivebooksedited
orwrittenbytheauthor(suchas“AppliedSurfactants”,Wiley,2005;“Encyclopedia
ofColloidandInterfaceScience”,Springer,2013).
Thisbookstartswithageneralintroduction(Chapter1)tointroducethesubject
andexplainthebookstructure.Chapter2givesageneralclassificationofsurfactants
basedonthenatureoftheheadgroup(anionic,cationic,zwitterionicandnonionic),
adescriptionofsomespecializedmoleculessuchasfluorocarbonandsiliconesur-
factants (referred to as superwetters), sugar-based surfactants, naturally occurring
surfactantsandpolymericsurfactants.Chapter3dealswiththeunusualproperties
ofsurfactantsolutionsandtheprocessofmicellization.Thedifferentself-assembly
structures that are produced in surfactant solutions are described in terms of their
structuresandphasebehavior.Chapter4describestheprocessofsurfactantadsorp-
tionattheair/liquid(A/L),liquid/liquid(L/L)andsolid/liquid(S/L)interfaces.The
experimentaltechniquesthatcanbeappliedformeasuringsurfactantadsorptionat
variousinterfacesarebrieflydescribed.Chapter5describestheuseofsurfactantsas
emulsifierswithparticularattentiontothemethodsthatcanbeappliedforselection
ofemulsifiersforagivenoilusedintheemulsion.Theroleofsurfactantsinstabilizing
theemulsionagainstflocculation,Ostwaldripeningandcoalescenceisalsodescribed
atafundamentallevel.Chapter6describestheuseofsurfactantsasdispersantsfor
suspensions. The process of dispersion of powders in liquids is described in terms
ofwetting,dispersionandstabilizationoftheresultingsuspensionagainstfloccula-
tion.Chapter7dealswithsurfactantsinfoamformationandstabilization.Thetheo-
riesoffoamstabilizationandtheroleofsurfactantsaredescribed.Applicationofsur-
factantsinformulationofnanoemulsions(withsizerange20–200nm)isdescribedin
vi | Preface
Chapter8.Thevariousmethodsthatcanbeappliedforpreparationofnanoemulsions
aredescribed.Chapter9describesmicroemulsionsandtheoriginoftheirthermody-
namic stability. The various methods that can be applied for formulation of micro-
emulsionsaredescribed.Theuseofsurfactantsaswettingagentswillbedescribedin
Chapter10.Particularattentionisgiventothefundamentalsofwettingandspreading
withparticularreferencetosurfactantsthatcanbeusedaswettingagents.Thefinal
Chapter11dealswithapplicationsofsurfactantsinselectedindustries:Cosmetics–
Pharmaceuticals–Agrochemicals–PaintsandCoatings–Detergents.
Thisbookcanbeusefulforteachingundergraduateandgraduatestudents.Itis
alsovaluableforindustrialchemistswhoareinvolvedinformulationofdispersesys-
tems,wheresurfactantsareessentialingredientsinsuchformulations.
Berkshire,2014
TharwatF.Tadros
Contents
Preface|v
1 Generalintroduction|1
2 Generalclassificationofsurfactants|5
2.1 Anionicsurfactants|5
2.1.1 Carboxylates|6
2.1.2 Sulfates|6
2.1.3 Sulfonates|7
2.1.4 Isethionates|8
2.1.5 Taurates|9
2.1.6 Phosphate-containinganionicsurfactants|9
2.2 Cationicsurfactants|9
2.3 Amphoteric(zwitterionic)surfactants|11
2.4 Nonionicsurfactants|12
2.4.1 Alcoholethoxylates|12
2.4.2 Alkylphenolethoxylates|13
2.4.3 Fattyacidethoxylates|13
2.4.4 Sorbitanestersandtheirethoxylatedderivatives(Spansand
Tweens)|13
2.4.5 Ethoxylatedfatsandoils|15
2.4.6 Amineethoxylates|15
2.4.7 Amineoxides|15
2.5 Specialitysurfactants|16
2.5.1 Fluorocarbonandsiliconesurfactants|16
2.5.2 Geminisurfactants|17
2.5.3 Surfactantsderivedfrommono-andpolysaccharides|17
2.5.4 Naturallyoccurringsurfactants|18
2.5.5 Biosurfactants|22
2.5.6 Polymericsurfactants|24
3 Aggregationofsurfactants,self-assemblystructures,liquidcrystalline
phases|29
3.1 Thermodynamicsofmicellization|36
3.1.1 Kineticaspects|36
3.1.2 Equilibriumaspects:Thermodynamicsofmicellization|37
3.2 Enthalpyandentropyofmicellization|39
3.3 Drivingforceformicelleformation|40
3.4 Micellizationinsurfactantmixtures(mixedmicelles)|42
viii | Contents
3.5 Surfactantself-assembly|45
3.5.1 Structureofliquidcrystallinephases|45
3.5.2 Hexagonalphase|46
3.5.3 Micellarcubicphase|47
3.5.4 Lamellarphase|47
3.5.5 Bicontinuouscubicphases|47
3.5.6 Reversedstructures|47
3.6 Experimentalstudiesofthephasebehaviorofsurfactants|48
4 Surfactantadsorptionatinterfaces|51
4.1 Introduction|51
4.2 Adsorptionofsurfactantsattheair/liquid(A/L)andliquid/liquid(L/L)
interfaces|52
4.2.1 TheGibbsadsorptionisotherm|53
4.2.2 Equationofstateapproach|57
4.2.3 TheLangmuir,SzyszkowskiandFrumkinequations|58
4.3 Interfacialtensionmeasurements|59
4.3.1 TheWilhelmyplatemethod|59
4.3.2 Thependentdropmethod|60
4.3.3 TheDuNouy’sringmethod|61
4.3.4 Thedropvolume(weight)method|61
4.3.5 Thespinningdropmethod|61
4.4 Adsorptionofsurfactantsatthesolid/liquidinterface|62
4.4.1 Adsorptionofionicsurfactantsonhydrophobicsurfaces|64
4.4.2 Adsorptionofionicsurfactantsonpolarsurfaces|67
4.4.3 Adsorptionofnonionicsurfactants|69
5 Surfactantsasemulsifiers|73
5.1 Introduction|73
5.1.1 Natureoftheemulsifier|73
5.1.2 Structureofthesystem|74
5.1.3 Breakdownprocessesinemulsions|74
5.2 Physicalchemistryofemulsionsystems|77
5.2.1 Theinterface(Gibbsdividingline)|77
5.2.2 Thermodynamicsofemulsionformationandbreakdown|78
5.2.3 Interactionenergies(forces)betweenemulsiondropletsandtheir
combinations|80
5.3 Mechanismofemulsification|85
5.3.1 Methodsofemulsification|86
5.3.2 Roleofsurfactantsinemulsionformation|88
5.3.3 Roleofsurfactantsindropletdeformation|89
5.4 Selectionofemulsifiers|92
Contents | ix
5.4.1 TheHydrophilic-LipophileBalance(HLB)concept|92
5.4.2 ThePhaseInversionTemperature(PIT)concept|95
5.5 Stabilizationofemulsions|97
5.5.1 Creamingorsedimentationanditsprevention|97
5.5.2 Flocculationofemulsionsanditsprevention|98
5.5.3 Ostwaldripeninganditsreduction|99
5.5.4 Emulsioncoalescenceanditsprevention|100
6 Surfactantsasdispersantsandstabilizationofsuspensions|103
6.1 Introduction|103
6.2 Roleofsurfactantsinpreparationofsolid/liquiddispersions
(suspensions)|103
6.2.1 Roleofsurfactantsincondensationmethods.Nucleationand
growth|104
6.2.2 Emulsionpolymerization|105
6.2.3 Dispersionpolymerization|107
6.2.4 Roleofsurfactantsindispersionmethods|109
6.3 Assessmentofwettabilityofpowders|115
6.3.1 Sinkingtime,submersionorimmersiontest|115
6.3.2 Measurementofcontactanglesofliquidsandsurfactantsolutionson
powders|116
6.3.3 Listofwettingagentsforhydrophobicsolidsinwater|116
6.3.4 Stabilizationofsuspensionsusingsurfactants|118
7 Surfactantsforfoamstabilization|121
7.1 Introduction|121
7.2 Foampreparation|121
7.3 Foamstructure|122
7.4 Classificationoffoamstability|123
7.4.1 Drainageandthinningoffoamfilms|124
7.4.2 Theoriesoffoamstability|125
7.5 Foaminhibitors|129
7.5.1 Chemicalinhibitorsthatlowerviscosityandincreasedrainage|130
7.5.2 Solubilizedchemicalswhichcauseantifoaming|130
7.5.3 Dropletsandoillenseswhichcauseantifoamingand
defoaming|130
7.5.4 Surfacetensiongradients(inducedbyantifoamers)|131
7.5.5 Hydrophobicparticlesasantifoamers|131
7.5.6 Mixturesofhydrophobicparticlesandoilsasantifoamers|132
7.6 Assessmentoffoamformationandstability|132
7.6.1 Efficiencyandeffectivenessofafoamingsurfactant|133