Lecture 3 - Emulsion Technology HLB

Question 1

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

Answer 1

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

Question 2

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

Answer 2

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

Question 3

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

Answer 3

strongly polar/has a charged ionic structure

Question 4

HLB definition and purpose

Answer 4

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

Question 5

Range of HLB

Answer 5

1 - 20

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

Question 6

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

Answer 6

• 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

Question 7

General structure of anionic surfactants

Answer 7

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

Question 8

4 types of anionic surfactants

Answer 8

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

Question 9

General properties of anionic surfactants

Answer 9

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

Question 10

soap

Answer 10

• 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.

Question 11

sodium lauryl sulfate

Answer 11

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

Question 12

sodium borate

Answer 12

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

Question 13

sodium cetearyl sulfate

Answer 13

• Anionic emulsifier (cetyl/ stearyl)

- Works well in lamellar network systems with fatty alcohols

Question 14

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

Answer 14

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

Question 15

Fatty alcohol ether phosphate (oleth-3 phosphate)

Answer 15

• 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

Question 16

Acyl Lactylates

Answer 16

• 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)

Question 17

phosphate esters (potassium cetyl phosphate)

Answer 17

• 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

Question 18

general structure of cationic surfactants

Answer 18

• 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

Question 19

Two types of cationic surfactants

Answer 19

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

Question 20

Distearyl Dimonium Chloride

Answer 20

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

Question 21

general structure of nonionic surfactants

Answer 21

• 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

Question 22

5 types of nonionic surfactants

Answer 22

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

Question 23

properties of nonionic emulsifiers

Answer 23

• broadly compatible with all ionic types

- best stability and effectiveness is achieved through combinations of emulsifiers

Question 24

monoglycerides

Answer 24

• Coemulsifiers-GMS, GMO

- Key components of emulsion gel networks

Question 25

fatty alcohols

Answer 25

- 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).

Question 26

ethoxylation

Answer 26

- 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)

Question 27

What is n in ethoxylation?

Answer 27

average number of ethylene oxide units (EO)

Question 28

Esters: Ethoxylated Carboxylic Acids PEG Esters

Answer 28

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

Question 29

Ethoxylated Glycerides

Answer 29

Ethoxylation of: - Monoglycerides - Hydroxyl fatty acid glycerides (castor oil, etc.) - Natural triglycerides

Question 30

sorbitan esters

Answer 30

- formed by acylation of sorbitan or sorbitol | - monostearate acts as coemulsifier and has low HLB

Question 31

Polysorbates

Answer 31

- formed by ethoxylation of sorbitan esters ( ~POE 20) - act as primary emulsifier - high HLB

Question 32

how are sorbitan esters named

Answer 32

- by acyl group attached | - ex. Sorbitan monostearate, Sorbitan trioleate

Question 33

how are polysorbates named (20 mole ethoxylated)

Answer 33

- named by numbers | - ex. 20 = lauryl (C12), 40- cetyl/palmityl (C16)

Question 34

decyl glucoside

Answer 34

foaming nonionic for cleansers (C10)

Question 35

cetearyl glucoside

Answer 35

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

Question 36

alkylpolyglucosides

Answer 36

- 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.

Question 37

polyglycerol esters

Answer 37

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

Question 38

esters

Answer 38

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

Question 39

sucrose esters

Answer 39

- 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

Question 40

lecithin

Answer 40

- 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

Question 41

4 types of silicone surfactants

Answer 41

- Dimethicone copolyols (alkoxylated EO & PO) - Silicone quaterniums - Silicone phosphates - Silicone esters

Question 42

Alkyl Dimethicone Copolyol

Answer 42

- W/O emulsifier | - Used to make “water resistant” w/o sunscreen creams