Lecture 3 - Emulsion Technology HLB Flashcards
a surfactant becomes more hydrophobic when it has what 3 things:
- a longer hydrocarbon tail
- more tails (double chained as opposed to single chained)
- a smaller nonionic head group
a surfactant becomes more hydrophilic when it has what 3 things:
- is ionic (anionic more typical of emulsifiers)
- has more head group units (moles of EO, polyglycerol)
- has a shorter tail
general property of the hydrophilic (“head group”) of the surfactant/emulsifier
strongly polar/has a charged ionic structure
HLB definition and purpose
- Hydrophile Lipophile Balance
- measure of how hydrophobic a surfactant is
- purpose is to give you idea of how a NONIONIC surfactant will perform
Range of HLB
1 - 20
with 1 most hydrophobic and 20 most hydrophilic (water soluble)
What does HLB Theory not take into account? (6 things)
- Electrical double layer effects of ionics
- Temperature effects of nonionics
- Fatty alcohols (oil phase, Liquid crystalline gel phases)
- Concentration of emulsifier
- Phase volume
- Component interactions
General structure of anionic surfactants
R-X- M+
X can be: Carboxylate RCOO- Sulfonate RSO2O- Sulfate ROSO2O- Phosphate ROPO(OH)O-
Counter ion (M+) can be: Sodium (Na+), Potassium (K+), Ammonium (NH4+) TEA
4 types of anionic surfactants
- sulfur-based
- phosphate esters
- carboxylates (soaps)
- acylamino acids
General properties of anionic surfactants
- Most important ionic class of surfactants
- Principle cleansing and foaming agent
- Common emulsifier class = Negatively charged hydrophobe
soap
- anionic
- Inexpensive, very powerful emulsifiers.
- Use monovalent soaps as o/w emulsifiers and polyvalent soaps (insoluble) as w/o emulsifiers.
- Must be used at high pH
- Often gel over time (due to liquid crystal formation)
- Can be irritating. Increase TEWL.
sodium lauryl sulfate
- anionic
- Efficient
- use only for o/w emulsions
- Contributes electrolyte
- inexpensive
- can be irritating.
sodium borate
Inexpensive, powerful w/o emulsifier. Use at a ratio of 16-20:1 (beeswax:borax).
sodium cetearyl sulfate
- Anionic emulsifier (cetyl/ stearyl)
- Works well in lamellar network systems with fatty alcohols
Amphisol (Amphisol K) or DEA(POTASSIUM)-CETYL PHOSPHATE
- Good for o/w emulsions (sunscreens)
- Requires high temperature (80-90C)
- Used in water resistant Sunscreens
Fatty alcohol ether phosphate (oleth-3 phosphate)
- Neutralize with amine to form anionic emulsifiers
- Mono or diesters are available (usually at 1:2 ratio)
- Efficient emulsifiers (0.3-1.5% use level)
- Don’t use below pH 5.0 as they can hydrolyze and release phosphoric acid
Acyl Lactylates
- R can be Lauroyl or Stearoyl
- Used in facial cleansers and lotions
- Used in combination with other anionics-foam boosting
- Stearyl used as food grade emulsifier (Promote liquid crystal formation)
phosphate esters (potassium cetyl phosphate)
- complex mixtures of mono, di and tri esters
- R can be a fatty alcohol group or H
- Mono & Di esters are very mild-used in skin cleansers
general structure of cationic surfactants
- usually a quaternary nitrogen
- non bound counter ion can be:
chloride (Cl-)
sulfonate (R-SO3-) - R can be either H, alkyl, benzyl, amide
- Most commonly found in hair conditioners
- Some skin care applications (emulsifier/emollient)
- Low pH
Two types of cationic surfactants
- Alkyl Amines
- Quaternary Ammonium Chlorides
- -Monoalkyl (Cetyl Trimonium Chloride)
- -Dialkyl ( Distearyl Dimonium Chloride)
Distearyl Dimonium Chloride
- Cationic conditioning emulsifier
- Antistatic agent
- Cationic skin care –Curel, Aveeno
- Hair Conditioners
general structure of nonionic surfactants
- Nonionic surfactants have no separate counterion like anionic and cationic surfactants
- The water soluble portion is based on polar carbon-oxygen functionality and hydrogen bonding
5 types of nonionic surfactants
- ethers
- amine oxides
- alkanolamides
- esters
- silicone emulsifiers (EO/PO)
properties of nonionic emulsifiers
- broadly compatible with all ionic types
- best stability and effectiveness is achieved through combinations of emulsifiers
monoglycerides
- Coemulsifiers-GMS, GMO
- Key components of emulsion gel networks
fatty alcohols
- Fatty alcohols are very slightly surface active
- Important in LQ Gel networks
- They are often used as a source for the hydrophobic tail (C8 - C20).
- Also, polypropylene oxide (PPG).
ethoxylation
- Treatment of alcohols with ethylene oxide adds units of EO
- Result is a range of “n” with average being the character of the product (Ex: steareth-10)
What is n in ethoxylation?
average number of ethylene oxide units (EO)
Esters: Ethoxylated Carboxylic Acids
PEG Esters
- Carboxylic acid + ethylene oxide
- Ester of Carboxylic acid and PEG
- A range of n ethoxylated units is produced
Ethoxylated Glycerides
Ethoxylation of:
- Monoglycerides
- Hydroxyl fatty acid glycerides (castor oil, etc.)
- Natural triglycerides
sorbitan esters
- formed by acylation of sorbitan or sorbitol
- monostearate acts as coemulsifier and has low HLB
Polysorbates
- formed by ethoxylation of sorbitan esters ( ~POE 20)
- act as primary emulsifier
- high HLB
how are sorbitan esters named
- by acyl group attached
- ex. Sorbitan monostearate, Sorbitan trioleate
how are polysorbates named (20 mole ethoxylated)
- named by numbers
- ex. 20 = lauryl (C12), 40- cetyl/palmityl (C16)
decyl glucoside
foaming nonionic for cleansers (C10)
cetearyl glucoside
moderately high HLB emulsifier with residual Cetearyl alcohol forms liquid crystalline gel networks for emulsion stabilization (C16-C18)
alkylpolyglucosides
- Reaction product of fatty alcohol + glucose gives between 1 and 4 glucose hydrophilic units
- Average degree of polymerization is 1.4
- excellent foamers & emulsifiers and very mild.
polyglycerol esters
- Polyglycerols from glycerine (C3) dehydration polymerization under alkaline conditions
- Esterified with fatty acids
- HLB ranges from 3-13
- W/O and O/W
esters
The acylation of glucose and sucrose gives esters with the sugar forming the hydrophilic group.
sucrose esters
- Food/pharma/cosmetic grade emulsifiers
- Sucrose has 8 hydroxy groups for esterification- most are mixtures of mono-,di- & tri-esters
- Stearates predominate, but available as laurates, oleate, behenates, erucates, palmitates
- HLB ranges from ~1-16
- Non-irritating
- Biodegradeable
lecithin
- 60% active in soybean oil and 95% granules (acetone insolubles)
- HLB ~ 4 : Diacyl phosphoglyceride
- High purity phosphatidyl choline forms liposomes
- Also contains – phosphatidyl ethanolamine , phosphatidyl inositol
4 types of silicone surfactants
- Dimethicone copolyols (alkoxylated EO & PO)
- Silicone quaterniums
- Silicone phosphates
- Silicone esters
Alkyl Dimethicone Copolyol
- W/O emulsifier
- Used to make “water resistant” w/o sunscreen creams
