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Skin Care Ingredients & Formulations > Lecture 3 - Emulsion Technology HLB > Flashcards

Lecture 3 - Emulsion Technology HLB Flashcards

1
Q

a surfactant becomes more hydrophobic when it has what 3 things:

A
  • a longer hydrocarbon tail
  • more tails (double chained as opposed to single chained)
  • a smaller nonionic head group
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2
Q

a surfactant becomes more hydrophilic when it has what 3 things:

A
  • is ionic (anionic more typical of emulsifiers)
  • has more head group units (moles of EO, polyglycerol)
  • has a shorter tail
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3
Q

general property of the hydrophilic (“head group”) of the surfactant/emulsifier

A

strongly polar/has a charged ionic structure

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4
Q

HLB definition and purpose

A
  • Hydrophile Lipophile Balance
  • measure of how hydrophobic a surfactant is
  • purpose is to give you idea of how a NONIONIC surfactant will perform
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5
Q

Range of HLB

A

1 - 20

with 1 most hydrophobic and 20 most hydrophilic (water soluble)

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6
Q

What does HLB Theory not take into account? (6 things)

A
  • 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
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7
Q

General structure of anionic surfactants

A

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
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8
Q

4 types of anionic surfactants

A
  • sulfur-based
  • phosphate esters
  • carboxylates (soaps)
  • acylamino acids
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9
Q

General properties of anionic surfactants

A
  • Most important ionic class of surfactants
  • Principle cleansing and foaming agent
  • Common emulsifier class = Negatively charged hydrophobe
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10
Q

soap

A
  • 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.
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11
Q

sodium lauryl sulfate

A
  • anionic
  • Efficient
  • use only for o/w emulsions
  • Contributes electrolyte
  • inexpensive
  • can be irritating.
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12
Q

sodium borate

A

Inexpensive, powerful w/o emulsifier. Use at a ratio of 16-20:1 (beeswax:borax).

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13
Q

sodium cetearyl sulfate

A
  • Anionic emulsifier (cetyl/ stearyl)

- Works well in lamellar network systems with fatty alcohols

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14
Q

Amphisol (Amphisol K) or DEA(POTASSIUM)-CETYL PHOSPHATE

A
  • Good for o/w emulsions (sunscreens)
  • Requires high temperature (80-90C)
  • Used in water resistant Sunscreens
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15
Q

Fatty alcohol ether phosphate (oleth-3 phosphate)

A
  • 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
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16
Q

Acyl Lactylates

A
  • 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)
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17
Q

phosphate esters (potassium cetyl phosphate)

A
  • 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
18
Q

general structure of cationic surfactants

A
  • 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
19
Q

Two types of cationic surfactants

A
  • Alkyl Amines
  • Quaternary Ammonium Chlorides
  • -Monoalkyl (Cetyl Trimonium Chloride)
  • -Dialkyl ( Distearyl Dimonium Chloride)
20
Q

Distearyl Dimonium Chloride

A
  • Cationic conditioning emulsifier
  • Antistatic agent
  • Cationic skin care –Curel, Aveeno
  • Hair Conditioners
21
Q

general structure of nonionic surfactants

A
  • 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
22
Q

5 types of nonionic surfactants

A
  • ethers
  • amine oxides
  • alkanolamides
  • esters
  • silicone emulsifiers (EO/PO)
23
Q

properties of nonionic emulsifiers

A
  • broadly compatible with all ionic types

- best stability and effectiveness is achieved through combinations of emulsifiers

24
Q

monoglycerides

A
  • Coemulsifiers-GMS, GMO

- Key components of emulsion gel networks

25
Q

fatty alcohols

A
  • 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).
26
Q

ethoxylation

A
  • 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)

27
Q

What is n in ethoxylation?

A

average number of ethylene oxide units (EO)

28
Q

Esters: Ethoxylated Carboxylic Acids

PEG Esters

A
  • Carboxylic acid + ethylene oxide
  • Ester of Carboxylic acid and PEG
  • A range of n ethoxylated units is produced
29
Q

Ethoxylated Glycerides

A

Ethoxylation of:

  • Monoglycerides
  • Hydroxyl fatty acid glycerides (castor oil, etc.)
  • Natural triglycerides
30
Q

sorbitan esters

A
  • formed by acylation of sorbitan or sorbitol

- monostearate acts as coemulsifier and has low HLB

31
Q

Polysorbates

A
  • formed by ethoxylation of sorbitan esters ( ~POE 20)
  • act as primary emulsifier
  • high HLB
32
Q

how are sorbitan esters named

A
  • by acyl group attached

- ex. Sorbitan monostearate, Sorbitan trioleate

33
Q

how are polysorbates named (20 mole ethoxylated)

A
  • named by numbers

- ex. 20 = lauryl (C12), 40- cetyl/palmityl (C16)

34
Q

decyl glucoside

A

foaming nonionic for cleansers (C10)

35
Q

cetearyl glucoside

A

moderately high HLB emulsifier with residual Cetearyl alcohol forms liquid crystalline gel networks for emulsion stabilization (C16-C18)

36
Q

alkylpolyglucosides

A
  • 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.
37
Q

polyglycerol esters

A
  • Polyglycerols from glycerine (C3) dehydration polymerization under alkaline conditions
  • Esterified with fatty acids
  • HLB ranges from 3-13
  • W/O and O/W
38
Q

esters

A

The acylation of glucose and sucrose gives esters with the sugar forming the hydrophilic group.

39
Q

sucrose esters

A
  • 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
40
Q

lecithin

A
  • 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
41
Q

4 types of silicone surfactants

A
  • Dimethicone copolyols (alkoxylated EO & PO)
  • Silicone quaterniums
  • Silicone phosphates
  • Silicone esters
42
Q

Alkyl Dimethicone Copolyol

A
  • W/O emulsifier

- Used to make “water resistant” w/o sunscreen creams

Skin Care Ingredients & Formulations (7 decks)

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