Cosmetic Product Stability
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Product StabilityProduct StabilityWhat is it?What is it?
How do we test it?How do we test it?
How can we improve it?How can we improve it?
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Product StabilityProduct StabilityWhat is it?What is it?
How do we test it?How do we test it?
How can we improve it?How can we improve it?
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Definition of StabilityDefinition of Stability
In mathematics, stability theory addresses theIn mathematics, stability theory addresses the
stability of solutions of differential equations andstability of solutions of differential equations and
of trajectories of dynamical systems under smallof trajectories of dynamical systems under small
perturbations of initial conditions.perturbations of initial conditions.
In probability theory, the stability of a randomIn probability theory, the stability of a random
variable is the property that a linear combinationvariable is the property that a linear combination
of two independent copies of the variable hasof two independent copies of the variable has
the same distribution, up to location and scalethe same distribution, up to location and scale
parameters. ...parameters. ...
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Definition of StabilityDefinition of Stability
-- the quality of being enduring and freethe quality of being enduring and free
from change or variationfrom change or variation
-- resistant to change of position orresistant to change of position or
conditioncondition -- firm and dependable; subject to littlefirm and dependable; subject to little
fluctuationfluctuation
-- not taking part readily in chemicalnot taking part readily in chemicalchangechange
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Definition of StabilityDefinition of Stability
What do we understand about it with regard toWhat do we understand about it with regard to
cosmetic products?cosmetic products?
That a product remainThat a product remainfit for purposefit for purpose
AppearanceAppearance Purity including lack of microbial contaminationPurity including lack of microbial contamination
EfficacyEfficacy
That it remains fit for purpose for a period of notThat it remains fit for purpose for a period of not
less than 36 months from manufacture and notless than 36 months from manufacture and not
less than its PAO declarationless than its PAO declaration
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Examples of InstabilityExamples of Instability
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Examples of InstabilityExamples of Instability
ObviousObvious
Emulsion breakdownEmulsion breakdown
Perfume changesPerfume changes
Colour changesColour changes Viscosity changesViscosity changes
Fungal growthFungal growth
Wax crystallisationWax crystallisation
Sediment in clear lotionsSediment in clear lotions
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Examples of InstabilityExamples of Instability
Less ObviousLess Obvious
pH changespH changes
Loss of activityLoss of activity
VitaminsVitaminsAntioxidantsAntioxidants
EnzymesEnzymes
PreservativesPreservatives
PhotoPhoto--degradation of UV filtersdegradation of UV filters Microbial growthMicrobial growth
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Emulsion CreamingEmulsion Creaming
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4 days at room temperature 1 month at 45C1 month at room temperature
4 days at room temperature 1 month at room temperature
1 month at 45C
Emulsion BreakdownEmulsion Breakdown
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Viscosity ChangesViscosity Changes
0
10
20
30
40
50
60
70
Initial 5 days 10 15 20 25 30 days
Increasing Decreasing Stable
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Worst Nightmare!Worst Nightmare!
Atmospheric Mould Colonies
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Crystal GrowthCrystal Growth
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Product StabilityProduct StabilityWhat is it?What is it?
How do we test it?How do we test it?
How can we improve it?How can we improve it?
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Testing for StabilityTesting for Stability
Prepare a pilot batch and store it in itsPrepare a pilot batch and store it in its
retail packaging and check that it remainsretail packaging and check that it remains
fit for purpose for a period of not less thanfit for purpose for a period of not less than
36 months from manufacture and not less36 months from manufacture and not lessthan its PAO declaration!than its PAO declaration!
ImpracticalImpractical
What other options?What other options?
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Testing SchedulesTesting Schedules
Examples of suitable schedules are givenExamples of suitable schedules are given
in the IFSCC Monographin the IFSCC Monograph
Boots publishes a scheme that itsBoots publishes a scheme that itssuppliers are expected to usesuppliers are expected to use --GR10GR10
Distance Learning Course (DLC) includesDistance Learning Course (DLC) includes
suggestions in its module on stabilitysuggestions in its module on stability
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Testing SchedulesTesting Schedules
IFSCC MonographIFSCC Monograph
4400 ambient humidityambient humidity -- retain as controlretain as control
202000 / 25/ 2500 ambient humidityambient humidity -- 60 months60 months
373700 ambient humidityambient humidity -- 6 months6 months
454500 ambient humidityambient humidity -- 3 months3 months
373700 &&80% relative humidity80% relative humidity -- 1 month1 month
Freeze / ThawFreeze / Thaw Light exposureLight exposure
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Testing SchedulesTesting Schedules
DLC RecommendationsDLC Recommendations
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DLC RecommendationsDLC Recommendations
1 month assessment (all storage conditions)
2 month assessment (all storage conditions)
3 month assessment (all storage conditions)
6 month assessment (all storage conditions)
9 month assessment (all storage conditions)
1 year assessment (all storage conditions)
18 month assessment (5C and RT storage conditions only)
2 year assessment (5C and RT storage conditions only)
30 month assessment (5C and RT only)
3 year assessment (5C and RT storage conditions only).
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Testing SchedulesTesting Schedules
Boots recommendation - Stability and final pack compatibility of all cosmeticand toiletry products should be assessed to establish that they are stableand that no separation, crystallisation, contamination, degradation or otherinstability occurs within the claimed product shelf life
40C0C to 30CProducts sold in tropical
climates
30C0C to 23CProducts sold in temperate
climates
Must be safe to use,
effective
and stable in final packfor at least 3 months at:
Must be safe to use,
effective
and stable in final packfor at least 36 months at:
Stability Requirements
Product must also be safe to use within their specified Period After Opening (PAO),
no matter at what point in their shelf life they are first opened.
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What should be checked?What should be checked?
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What is ImportantWhat is Important
Consider thefunctionof the product under test anddecide whether or not the changes observed could affectthis
Consider thesafetyof the product under test and decidewhether or not the changes observed could affect this
Consider whether the changes observed affect theaestheticsof the product under test
Note under what storage conditions any changesobserved take place and try to relate these to theenvironment in which the product is to be sold
Look for significant trends in changes of productattributes
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Talking PointsTalking Points
What is important for this product in thisWhat is important for this product in this
packaging for this market?packaging for this market?
Setting product specificationSetting product specification
Minimum and maximum for each parameterMinimum and maximum for each parameterWhy these numbers?Why these numbers?
Have products been prepared and tested atHave products been prepared and tested at
extreme specification limits?extreme specification limits?
Release specifications / shelfRelease specifications / shelf--life specificationslife specificationsWhat matters?What matters?
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Accelerated Testing for StabilityAccelerated Testing for Stability
Prepare a pilot batch and store it in its retailPrepare a pilot batch and store it in its retail
packaging:packaging:--
Room Temperature (RT) for 24 monthsRoom Temperature (RT) for 24 months
44C for 3 monthsC for 3 months 4040C for 3 monthsC for 3 months
44C/40C/40C Cycle for a number of cyclesC Cycle for a number of cycles
In a NIn a N--facing window or a light box for 3mfacing window or a light box for 3m
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Testing for StabilityTesting for Stability
Monitor for changes in appearanceMonitor for changes in appearance(Subjective measurements)(Subjective measurements)
HomogeneityHomogeneity
ColourColourGlass slidesGlass slides
MicroscopeMicroscope
Texture and skin feelTexture and skin feel
OdourOdour
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Testing for StabilityTesting for Stability
Monitor emulsion stabilityMonitor emulsion stability(Physical changes)(Physical changes)
Emulsion breakdownEmulsion breakdown Creaming or settlingCreaming or settling
Glass slidesGlass slidesaeration and density/opacityaeration and density/opacity MicroscopeMicroscope droplet size changes; crystalsdroplet size changes; crystals
Viscosity changesViscosity changes
Rheological changesRheological changes
Centrifuge testsCentrifuge tests
TurbiscanTurbiscan LumifugeLumifuge
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Emulsion CreamingEmulsion Creaming
3 months at 40C 18 months at RT
What ways are available for quicker results
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4 days at room temperature1 month at 45C
1 month at room temperature
4 days at room temperature 1 month at 45C1 month at room temperature
Microscope ExaminationMicroscope Examination
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Viscosity ChangesViscosity Changes
These are actualviscosity graphsof 5 differentw/o emulsions
differing only inemulsifier used
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Rheological ChangesRheological Changes
For suspensions measure yield valuesFor suspensions measure yield values
Yield value is the minimum force necessary toYield value is the minimum force necessary to
induce flowinduce flow
Measured using a rheometer or a BrookfieldMeasured using a rheometer or a BrookfieldDigital Viscometer with small sample adaptorDigital Viscometer with small sample adaptor
Yield values may be used to determine theYield values may be used to determine the
suspending power of a composition; verysuspending power of a composition; very
useful when developing scrubsuseful when developing scrubs http://www.connock.co.uk/articles_exfoliants.htmhttp://www.connock.co.uk/articles_exfoliants.htm
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Accelerated Stability TestingAccelerated Stability Testing
CentrifugeCentrifuge 5 minutes or more at 5,000 rpm5 minutes or more at 5,000 rpm
UltracentrifugeUltracentrifuge
A centrifuge designed to run at very high speeds andA centrifuge designed to run at very high speeds andthus generate very high centrifugal force is called anthus generate very high centrifugal force is called an
ultracentrifuge.ultracentrifuge.
Suspensions which would settle only very slowly orSuspensions which would settle only very slowly or
not at all under gravity can be made to separatenot at all under gravity can be made to separate
quickly in such a device!quickly in such a device!
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The LUMiFuge
Demixing phenomena, like sedimentation, flotation or consolidation
are directly measured by the LUMiReader, LUMiFugeor
LUMiSizerdue to the patented cutting-edge STEP-Technology.
This permits to obtain Space- and Time-resolved Extinction Profiles
over the entire sample length of up to 12 different samples
simultaneously. Parallel light (I0) illuminates the entire sample cell
and the transmitted light I is detected by thousands of sensors
arranged linearly across your whole sample fromtop to bottom with
a microscale resolution. Transmission is converted into extinction by
lg I/I0 and particle concentration may be calculated.www.lum-gmbh.com/pages/.../lumifuge/products_lumifuge.htm
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The LumiFugeThe LumiFuge
The multisampleThe multisampleanalytical centrifugeanalytical centrifugeLUMiFugeLUMiFugeacceleratesacceleratesthe demixing process upthe demixing process upto 2300 times comparedto 2300 times compared
to traditional test tubeto traditional test tubetests. Stability tests andtests. Stability tests andshelfshelf--life determinationslife determinationsof original dispersions areof original dispersions areup to 2500 times fasterup to 2500 times fasterthan performed in a testthan performed in a test
tube under earth gravitytube under earth gravity..
http://www.lum-gmbh.com/pages/products/lumifuge/products_lumifuge.htm
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TurbiscanTurbiscan
The Turbiscanmeasures transmittedand reflected lightpassing through asample and graphs the
results. Differencesover time are due tochanges in droplet sizeand distribution
www.formulaction.com/stab_lab_gb.htm
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Particle size variation
Coalescence or flocculation
Particle migration
Sedimentation or creaming
t=0 min
t=15 min
t=0 min
t=15 min
Principle of Measurement
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Testing for StabilityTesting for Stability
Monitor chemical changesMonitor chemical changes
pHpH
Loss of activityLoss of activity
VitaminsVitaminsAntioxidantsAntioxidants
EnzymesEnzymes
PreservativesPreservatives
UV FiltersUV Filters
PhotoPhoto--degradation of UV filtersdegradation of UV filters
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Testing for StabilityTesting for Stability
Monitor preservative efficacyMonitor preservative efficacy
Initial challenge test to accepted protocolsInitial challenge test to accepted protocols
CTFA, CTPA, B.P. and European PharmacopoeiasCTFA, CTPA, B.P. and European Pharmacopoeias
Head space testHead space testIt is recommended that this be done if wideIt is recommended that this be done if wide--
mouthed container is used to assess risk of mouldmouthed container is used to assess risk of mould
and fungal growthand fungal growth
Challenge testing of stability samplesChallenge testing of stability samples
It is recommended that this be done after 3 monthsIt is recommended that this be done after 3 months
stability testing at RT and 40Cstability testing at RT and 40C
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Packaging CompatibilityPackaging Compatibility
STRESS CRACKINGSTRESS CRACKING--The Hedley TestThe Hedley Test
Applied to detergent/oil based products whichApplied to detergent/oil based products which
are contained in polythene, PVC, PET.are contained in polythene, PVC, PET.
12 samples filled to the declared volume and12 samples filled to the declared volume andclosure fitted to the correct torque.closure fitted to the correct torque.
Stored at 60Stored at 60C for 48 hours, 6 upright and 6C for 48 hours, 6 upright and 6
inverted.inverted.
At the end of the test no containers should showAt the end of the test no containers should showany signs of cracking.any signs of cracking.
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Packaging ProblemsPackaging Problems
Panelling of polyethylenePanelling of polyethylene
Dissolving of PVCDissolving of PVC
Oils causing brittle polystyreneOils causing brittle polystyrene
Corrosion of aluminiumCorrosion of aluminium Discolouration of plasticDiscolouration of plastic
Transpiration of perfume through plasticTranspiration of perfume through plastic
Absorption of actives by pack wallAbsorption of actives by pack wall Etc.Etc.
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Product StabilityProduct Stability
What is it?What is it?
How do we test it?How do we test it?
How can we improve it?How can we improve it?
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Emulsion StabilityEmulsion Stability
A two-phase system, consisting of twocompletely immiscible or partially miscibleliquids, one being dispersed in the other in
the form of very fine droplets Water-in-Oil = w/o
Oil-in-Water = o/w
Oil-in-Water-in-Silicone = o/w/Si
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Emulsion StabilityEmulsion Stability
What makes it stable?What makes it stable?
Correct choice of emulsifier systemCorrect choice of emulsifier system
Compatible ingredientsCompatible ingredients
Compatible pHCompatible pH Correct mixing methodCorrect mixing method
Compliance with specificationCompliance with specification
Compatible packagingCompatible packaging
Understanding possible causes of instabilityUnderstanding possible causes of instability
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Emulsion StabilityEmulsion Stability
What makes it stable?What makes it stable?
Correct choice of emulsifier systemCorrect choice of emulsifier system
Compatible ingredientsCompatible ingredients
Compatible pHCompatible pH Correct mixing methodCorrect mixing method
Compliance with specificationCompliance with specification
Compatible packagingCompatible packaging
Understanding possible causes of instabilityUnderstanding possible causes of instability
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HLB SystemHLB System
HLB Number = E + P
5
where
E = molecular weight percent of ethylene oxide content P = molecular weight percent of polyol content
In the equation above the value (E+P) can take on anyvalue up to a maximum of 100. This means that the HLB
number assigned to the emulsifier will lie within therange of 0 to 20.
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HLB SystemHLB System
HLB number of surfactant and type ofemulsion formed
< 3 none
3 8 water-in-oil (W/O) 8 15 oil-in-water (O/W)
> 15 solubilisation
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Liquid CrystalsLiquid Crystals
Some emulsifier systems form liquid crystal structures,Some emulsifier systems form liquid crystal structures,which contribute to stabilitywhich contribute to stability
Examples:Examples:
Cetearyl glucoside with cetearyl alcoholCetearyl glucoside with cetearyl alcohol
Sorbitan olivate and cetearyl olivateSorbitan olivate and cetearyl olivate
Sorbitan stearate with sorbityl laurateSorbitan stearate with sorbityl laurate
Sorbitan stearate with sucrose cocoateSorbitan stearate with sucrose cocoate
PolyglycerylPolyglyceryl--3 methylglucose distearate3 methylglucose distearate
Potassium cetyl phosphate and hydrogenated palmPotassium cetyl phosphate and hydrogenated palm
glyceridesglycerides Lauryl glucoside & polyglycerylLauryl glucoside & polyglyceryl--2 dipolyhydroxystearate2 dipolyhydroxystearate
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Liquid Crystal EmulsionLiquid Crystal Emulsion
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Liquid Crystal EmulsionLiquid Crystal Emulsion
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Other EmulsifiersOther Emulsifiers
Polymers e.g. Acrylates/C10-30 Alkyl AcrylateCrosspolymers
Polyethylene glycol ethers (Oleth-10; Laureth-10 etc)
Polysorbates with Sorbitan esters e.g. Polysorbate-20with Sorbitan monolaurate
Glyceryl esters e.g. Glyceryl cocoate / laurate etc.
Alkolylated dimethicones (AKA Dimethicone copolyols)
Soaps e.g. triethanolamine stearate; Potassiumpeanutate etc.
PG Esters e.g. Propylene glycol myristate etc.
Sucrose esters e.g. Sucrose laurate / myristate etc
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Emulsion StabilityEmulsion Stability
What makes it stable?What makes it stable?
Correct choice of emulsifier systemCorrect choice of emulsifier system
Compatible ingredientsCompatible ingredients
Compatible pHCompatible pH Correct mixing methodCorrect mixing method
Compliance with specificationCompliance with specification
Compatible packagingCompatible packaging
Understanding possible causes of instabilityUnderstanding possible causes of instability
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Incompatible IngredientsIncompatible Ingredients
Carbomers and saltsCarbomers and salts
Kathon CG contains a saltKathon CG contains a salt
Dihydroxyacetone and formaldehydeDihydroxyacetone and formaldehyde
Many preservatives are formaldehyde donorsMany preservatives are formaldehyde donors
Enzymes and chelating agentsEnzymes and chelating agents
EDTA and its saltsEDTA and its salts
ParabensParabens
EthoxylatedEthoxylatedemulsifiersemulsifiers etc. etc.etc. etc.
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pH vs ViscositypH vs Viscosity
84000
86000
88000
90000
92000
94000
96000
98000
100000
pH 5.0 pH 5.5 pH 6.0 pH 6.5 pH 7.0 pH 7.5 pH 8.0
Viscosity
Typical carbomer system
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Correct Mixing MethodsCorrect Mixing Methods
Use laboratoryUse laboratory
mixing equipmentmixing equipment
which representswhich represents
that availablethat availablein the factoryin the factory
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Pilot ScalePilot Scale
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Correct Mixing MethodsCorrect Mixing Methods
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Compliance with SpecificationCompliance with Specification
How was the specification set?How was the specification set? One small laboratory batch?One small laboratory batch?
2 or more laboratory batches with2 or more laboratory batches withreproducible results?reproducible results?
Pilot scale batch?Pilot scale batch?
Was stability tested on a product withinWas stability tested on a product withinthe specification set?the specification set? Better still; were 2 or more batches at limitsBetter still; were 2 or more batches at limits
of specification testedof specification tested
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Emulsion StabilityEmulsion Stability
What causes instability?What causes instability?
For an emulsion to become unstable thedispersed phase droplets must collide andcoalesce
Coalescence of two dispersed phasedroplets produces a bigger dispersedphase droplet, and the ultimate outcomeof this process is complete phaseseparation, indicating emulsion instability
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Forces of AttractionForces of Attraction
F = -Aa
12H
where
F = London-Van der Waals force of attraction
A = Hamaker constant
a = radius of the dispersed phase droplets
H = distance between two adjacent dispersed
phase droplets
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Forces of AttractionForces of Attraction
Good stuff but what does it mean forGood stuff but what does it mean for
emulsion stabilityemulsion stability
From the equation it can be seen that the
magnitude of the attractive force increasesas the radius of the dispersed phase
droplets becomes larger and less as thedistance between them is increased
Stability = Small droplets far apart
F = -Aa12H
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Stokes Law
Stokes Lawdescribes the factors influencing the velocityof a solid sphere, moving under the force of gravity, in acontinuous liquid medium
V = 2a2(cd)g
9
V = velocity of the dispersed phase droplet a = radius of the dispersed phase droplet d = density of the dispersed phase c = density of the continuous phase g = acceleration due to gravity = viscosity of the continuous phase
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Stokes Law: Good stuff but whatStokes Law: Good stuff but what
does it mean for emulsion stabilitydoes it mean for emulsion stabilityV = 2a2(cd)g
9
To improve stability reduce V
Reduce a - size of dispersed phase droplet
Reduce (pc-pd) by matching density of the dispersedphase with that of the continuous phase
g = acceleration due to gravity difficult to alter Increase - viscosity of the continuous phase
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What droplet size?What droplet size?
Emulsion appearance and approximateparticle size
milky-white greater than 1
blue-grey 1.0 - 0.1
translucent 0.1 - 0.05
transparent less than 0.05
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Emulsion StabilityEmulsion Stability
Careful selection of emulsifiersCareful selection of emulsifiers
Small droplet size (High shear mixing; PITSmall droplet size (High shear mixing; PITtechnology)technology)
Lamellar structures by using emulsifiersLamellar structures by using emulsifiersthat form liquid crystalsthat form liquid crystals
Match SG of oil phase to aqueous phaseMatch SG of oil phase to aqueous phase
Adjust rheological properties by usingAdjust rheological properties by using
carbomers or xanthan gum, starch or CMCcarbomers or xanthan gum, starch or CMCderivatives etc.derivatives etc.
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Add Rheological AdditiveAdd Rheological Additive
0% UltraThix P-100+ 0.5% Cerasynt 945
0.5% UltraThix P-100+ 0.2% Cerasynt 945
0.5%UltraThix P-100+ 0.5%
Cerasynt 945
Cerasynt 945 = Glyceryl stearate (&)laureth-23 Ultrathix P100 =
Acrylic acid/VP Crosspolymer
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Add Right Rheological AdditiveAdd Right Rheological Additive
Zinc Oxide nano particles
Carbomer Acrylic acid/VP Crosspolymer
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Microscope ExaminationMicroscope Examination
Titanium Dioxide Nano particles
Carbomer Acrylic acid/VP Crosspolymer
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Sun Protection ProductsSun Protection Products
These present special problemsThese present special problems
Emulsion stabilityEmulsion stability
Agglomeration of micronised sunscreensAgglomeration of micronised sunscreens
Crystallising of organic sunscreensCrystallising of organic sunscreens Failure to meet SPF declarationFailure to meet SPF declaration
Failure to meet UVA requirementsFailure to meet UVA requirements
Failure to meet water resistance claimsFailure to meet water resistance claims
Photodegradation of activesPhotodegradation of actives
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Sun Protection ProductsSun Protection Products
Agglomeration of micronised sunscreens canAgglomeration of micronised sunscreens can
be seen under a microscope at 1000xbe seen under a microscope at 1000x
magnificationmagnification
Use rheology modifiers to stop migration ofUse rheology modifiers to stop migration ofparticlesparticlesVeegum is good.Veegum is good. Acrylic acid/VPCrosspolymer is recommended
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Preventing AgglomerationPreventing Agglomeration
Zinc Oxide nano particles
Acrylic acid/VP Crosspolymer
TiO2 Nano particles
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Crystallising of Organic SunscreensCrystallising of Organic Sunscreens
Check solubility in oil phase
If using Phenylbenzimidazole Sulfonic AcidpH 7.3 - 7.7 is critical
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Photodegradation of BMDBMPhotodegradation of BMDBM
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Improve UV Absorber StabilityImprove UV Absorber Stability
The UVA filter BMDBM is not photostable and may lose 60% orThe UVA filter BMDBM is not photostable and may lose 60% ormore of its activity at 360nm when exposed to solar radiation.more of its activity at 360nm when exposed to solar radiation.
EHMC destabilises BMDBM / octocrylene mixturesEHMC destabilises BMDBM / octocrylene mixtures
BenzophenoneBenzophenone--3 stabilises BMDBM weakly; octocrylene stabilises3 stabilises BMDBM weakly; octocrylene stabilises
EHMC strongly but does not stabilise BMDBM and ethylhexylEHMC strongly but does not stabilise BMDBM and ethylhexylmethoxycrylene stabilises BMDBM strongly.methoxycrylene stabilises BMDBM strongly.
There is a relationship between the rate of photo decay of BMDBMThere is a relationship between the rate of photo decay of BMDBM
and the dielectric constant of the oil phase. As the dielectricand the dielectric constant of the oil phase. As the dielectric
constant increases BMDBM is progressively more stable until itconstant increases BMDBM is progressively more stable until it
reaches maximum stability at about 8.8, after which its rate ofreaches maximum stability at about 8.8, after which its rate of
decay increases againdecay increases again
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Sun Protection ProductsSun Protection Products
Failure to meet SPF declarationFailure to meet SPF declaration
Failure to meet UVA requirementsFailure to meet UVA requirements
Study the suppliers literature and many articles on theStudy the suppliers literature and many articles on the
subjectsubject
http://www.creativehttp://www.creative--developments.co.uk/papers/developments.co.uk/papers/
http://www.cosmeticsbusiness.com/section.asp?navcode=50http://www.cosmeticsbusiness.com/section.asp?navcode=50
DonDont put to much faith in SPF boosterst put to much faith in SPF boosters
Use the Ciba Sunscreen Simulator then inUse the Ciba Sunscreen Simulator then in--vitro then invitro then in--vivovivo
http://http://www.ciba.com/index/indwww.ciba.com/index/ind--index/indindex/ind--per_car/indper_car/ind--pcpc--uv/induv/ind--pcpc--uvuv--sss.htmsss.htm
Make sure the formula complies with latest EUMake sure the formula complies with latest EU
Recommendation (UVA =>1/3Recommendation (UVA =>1/3rdrd UVB)UVB)
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Thank you for your timeThank you for your timeand may all your creationsand may all your creations
be stablebe stable
John WoodruffJohn Woodruff
www.creativewww.creative--developments.co.ukdevelopments.co.uk