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Viscosity Control Flashcards

1
Q

Two primary purposes of adding thickeners

A
  • Enhancement of product form/aesthetics/application properties
  • Product Stability
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2
Q

Flow properties are determined by

A
  • particle-particle interaction
  • association structure disturbances
  • polymer behavior in solution
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3
Q

Define rheology

A

How materials deform or flow in response to external forces

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4
Q

Define shear stress

A

External force applied over area

Pa = N/m^2

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5
Q

Define shear rate

A 
velocity gradient (1/sec) 
HOW FAST
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6
Q

Define shear strain

A

Relative displacement

HOW FAR

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7
Q

Define viscosity

A

Measure of a material’s resistance to flow

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8
Q

Newtonian shear

A

linear response of flow rate to shear stress

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9
Q

Pseudoplastic refers to ______ rheology

A

Shear thinning

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10
Q

Dilatant refers to _________ rheology

A

Shear thickening

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11
Q

Thixotropic refers to _______ rheology

A

Shear thinning with time dependence

Slower return to original state

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12
Q

Thickening agents in external water phase in O/W emulsions

A

Hydrocolloids

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13
Q

Thickening agents in lipid phase in O/W emulsions

A
  • Co-emulsifiers

- Solid amphiphiles that form liquid crystalline gel networks

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14
Q

Factors governing O/W emulsion viscosity

A
  • Thickeners in water phase
  • Thickeners in lipid phase dispersed in water phase
  • Phase volume (Ratio—-Volume of dispersed phase: volume of continuous phase)
  • Lipid composition of internal phase
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15
Q

Examples of synthetic polymer thickeners

A
  • acrylates
  • carbomers
  • polyurethanes
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16
Q

Carbohydrates/plant/algal thickeners

A
  • Xanthan gum
  • Alginates
  • Scleroglucan
  • Carrageenan
  • Guar
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17
Q

Example of fermentation derived microbiological by-product thickeners

A

Gellan-exopolysaccharide from Sphingomonas elodea

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18
Q

Cellulose derivative thickeners

A

Carboxymethylcellulose

Hydroxyethylcellulose

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19
Q

Examples of smectite clay thickeners

A
  • Bentonites

- Hectorites

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20
Q

Dramatic viscosity increase occurs past the Critical Overlap Concentration due to

A

interaction of polymer molecules to form interpenetrating networks in the solvent

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21
Q

Associative rheology modifiers control rheology by

A

Association with:

  • itself
  • surfactant micelles
  • water dispersible clays
  • emulsified solvent phase
  • dispersed solids
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22
Q

Nonassociative rheology modifiers control rheology by

A

chain entanglement of lightly cross-linked polymer molecules

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23
Q

Liquid Dispersion polymers used as self-emulsifying system consist of

A

Polymer thickener (anionic/cationic/nonionic)
Emollient Solvent
Nonionic emulsifier

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24
Q

What portion of Agar is Agarose

A

neutral gelling portion separated from sulfate non-gelling portion

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25
What is agarose polymer made of
galactose and anhydrogalacose
26
Agarose gels are ___________ and are hydrated at _____ temperatures
thermoreversible | high
27
Agarose is derived from
Rhodophycae
28
Alginic Acid is derived from
Laminaria, Macrocystis, brown seaweeds
29
Acid sugars making up algal polysaccharides
Mannuronic, Guluronic
30
Form of alginic acid that acts as thickener
Sodium/Potassium alginate
31
Algin-derived thickeners exhibit __________ rheology, _____ sensitivity to heat, and _______ yield value
pseudoplastic shear thinning high little
32
Anionic forms of alginic acid complex with _______ to form _________
Divalent calcium ions | rigid gels
33
Having a high yield value leads to
increased stability at room temperature
34
Water swellable clays have ______ rheology
thixotropic
35
High solids dispersions tend to have ______ rheology
dilatant
36
What type of measurements does a viscometer give
Single point
37
What do rheometers measure
Give shear stress at a controlled shear rate
38
_______ phase is most important in finished product viscosity
Outer
39
Co-emulsifiers give
liquid gel network
40
Silicas work as thickeners by
hydrogen bonding
41
Hydrophobically modified polymers will act as thickeners by
associating with other hydrophobic materials OR have intermolecular bonding with other ingredients in solution
42
Which inorganic rheology modifier can also work in organic media
silica
43
greatest fault of carbomers
salt sensitivity
44
What is required for anionic polymers?
They must be neutralized with equivalent weight
45
What is difficult about carbomers once they have been neutralized?
Hard to thin out
46
Neutralizing Carbopol and Pemulen polymers in aqueous and hydroalcoholic solutions has this result
Hydroxyl groups associate to form cross links | Too much salt can break down the structure though
47
Describe the process of creating a liquid dispersion polymer
- Disperse polymer in liquid - add in HLB emulsifier - this thickens the water and inverts the emulsion
48
Croda's Liquid dispersion polymers
- Polyacrylate polymers dispersed in carrier oil with an inverting surfactant - Add to water--> turns into a w/o emulsion - Polyacrylate molecules swell by osmosis, thickening the water phase
49
The three forms of Carrageenan depend on
levels of sulfation
50
Chitosan is a ________ polymer
cationic
51
Chitosan can be used for ________
coacervation encapsulation
52
Scleroglucan has ______ rheology
pseudoplastic
53
Locust Bean Gum retards ice crystal growth by
forming structured gel at solid/liquid interface for freeze/thaw stabilization
54
Gellan comes from
bacterium
55
Xanthan gum exhibits ______ rheology
shear thinning
56
______ are used in the scale-up process for processing gums
Eductors
57
Microcrystalline cellulose is a product of
partial cellulose depolymerization by mineral acid
58
Microcrystalline cellulose colloidal dispersion acts as
emulsion stabilizer
59
CMC is used as a
dispersion agent
60
Polyquaternium-10 consists of
cationic group attached to hydroxycellulose
61
Smectite clays can be used in low levels due to
synergy with organic thickeners
62
Synthetic polymers are synthesized with
free radical initiators
63
Synthetic polymers are ________ likely to be sensitive to salt and pH than natural gums
more
64
Thickeners for anhydrous systems
- Aluminum Stearate - Trihydroxystearin - SiO2 - Organoclays - Polyethylene
65
Quat-18 is derived from
tallow
66
fatty quats react with smectite clay to
replace monovalent anions between clay platelets
67
Organic solvents have this effect on organoclays
interstitial space swelling

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