Formulating with Rheology Modifiers

“Formulating with Rheology Modifiers” 

SWSCC Suppliers’ Day 

August 23, 2012 

Cosmetic Division 

By Joseph Albanese 

3V Technical Marketing Manager 

Personal Care 

j.albanese@3vusa.com 

Tele: (908) 456-2968

• Rheology 

• Instruments 

• Rheology Modifiers 

• Formulation Tips 


Agenda 

2

Rheology Modifiers 

INCI Dictionary Functional Classes 

• Viscosity Controlling Agents 

• Viscosity Decreasing Agents 

• Viscosity Increasing Agents for Non-Aqueous 

Systems 

• Viscosity Increasing Agents for Aqueous 

Systems

So what then is the relationship 

of viscosity to rheology? 

• Viscosity measures the resistance 

(“internal friction”) of fluid or liquid to an 

applied stress or shear force. 

• Rheology is a complex study of the 

deformation and flow of matter. It is a 

branch of science. 


4

Ideal 

Liquid 

Rheology 

G*, G’, G”, Tan δ, etc. 

Ideal 

Solid 

Deform irreversibly Deform elastically 

Mineral Oil spring back unchanged 

G” (dynes/cm 2 ) = Viscous Modulus Steel Ball 

G” > G’ – effective viscosifier G’ (dynes/cm2) = Elastic Modulus 

G’ > G” – effective suspending agent 

Fluid Mechanics Rheology Solid Mechanics 

Newtonian Fluids Plasticity and Elasticity 

Non-Newtonian Fluids

Lord Kelvin 1804-1901 

“When you can measure what you 

are speaking about in numbers, 

you know something about it, 

but when you cannot measure it, 

when you cannot express it in 

numbers, your knowledge is of a 

meager and unsatisfactory kind; 

it may be the beginning of 

knowledge, but you have 

scarcely, in your thoughts, 

advanced to the stage of 

science.”

Viscosity 

• Viscosity (η) is the ratio of shear stress (σ) to shear rate (γ) 

and describes the resistance to flow of a liquid. 

Viscosity = Shear Stress / Shear Rate 

η = σ / γ 

Units: dynes-sec/cm 2 = poise = 100 centipoise (cp)

But what is “shear stress” and “shear rate”? 


Moving 

Liquid between two parallel plates 

Stationary 

8

Distance (d) 

Viscosity 

Stationary 

Shear Stress = Force / Area = dynes/cm 2 = N/m 2 

Dynes/cm 2 = 0.1 Pascal (Pa) 

N/m 2 = 1 Pascal (Pa) 

Shear Rate = Velocity / Thickness = (m/s)/m = 1/s = s -1 

The rate of change of shear stress. The velocity gradient perpendicular to the 

direction of shear flow (dv/dx). Units 1/s or s -1 


Area (A) Force (F) 

Moving 

Velocity (v)

Types of Rheological Behavior 

RHEOLOGY 

Newtonian Non-Newtonian 

Time Dependant Time Independent 

Rheopectic 

Thixotropic 

Dilatant 

Pseudoplastic

Types of Rheology 

• Newtonian – viscosity constant regardless of shear 

– Typical of many shampoos, water, mineral oil, glycerin 

• Pseudoplastic flow – shear thinning and immediate 

recovery 

– Viscosity decreases with an increase in shear rate 

– Typical of Carbomers and other Polyacrylates 

• Thixotropic flow – shear thinning and slow recovery 

– Viscosity decreases with time 

– Typical of clays and organoclays 

• Dilatant* – immediate shear thickening. Undesirable for 

cosmetics. 

• Rheopectic* – shear thickening over time 

* NOTE: Undesirable for cosmetics.

Shear Stress 


Newtonian Fluid 

A “thick” (viscous) 

liquid: high stress, 

low shear rate 

A “thin” (low viscosity) 

liquid: low stress, high 

shear rate 

Shear Rate 

Linear Relationship Constant Viscosity 

Viscosity 

A “thick” (high viscosity) liquid 

A “thin” (low viscosity) liquid 

Shear Rate 

Temperature must be kept constant. 

12

Shear Rate (velocity gradient) 

Dilatant 


Non-Newtonian 

Pseudoplastic 

Shear Stress (Force) 

Viscosity 

Pseudoplastic 

Dilatant 

Shear Rate 

13

Viscosity 

Viscosity vs. Typical Shear Rates 

Experienced by Products 

Thixotropic 

Pseudoplastic 

Newtonian 

Shear Rate (s-1 ) 

Storage Shipping Dispensing Application Homogenization

A Non-Newtonian Pool Party 


15

And now for a word from our sponsor . . . 


16

And now for a word from our sponsor . . .

Viscoelasticity of Silly Putty 

G” 

G’ ŋ 

G” > G’ more viscous 

Modulus = Shear Stress / Shear Strain 



G’ > G” more elastic 

SOURCE: http://www.campoly.com/general_research.html

SOURCE: http://www.technicianonline.com/multimedia/gallery-silly-putty-hits-hard-1.2602855 


19


Silly Putty Drop 

20


Agenda 

• The Science of Rheology 




21


Modes of Deformation 

All materials will strain or deform if a load or stress is applied. 

Linear 

Rotational 

Tensile Compression Bending 

Torsional Shear Rectangular Torsion 

22

Viscometer or Rheometer? 

Viscometer 

• Relatively low cost 

• Low to medium shear 

• Rotates in a one direction 

• Limited to more viscous 

materials 

• Suitable for simple flow 

measurements. 

• Portable enough to do remote 

testing 

• Highly suitable for QC 


Rheometer 

• Relatively very expensive 

• Very low to very high shear 

• Greater characterization of 

flow and deformation behavior 

• Oscillatory motion possible 

• Can apply large step changes 

in stress and strain to find both 

viscoelastic and flow 

properties 

• Can measure very low 

viscosity samples 

• Can do other tests under a 

wider range of conditions 

• Highly suitable or R&D & QC 

23

Viscometer or Rheometer? 


Approximate Velocity Gradients 

Shear Rate (1/s) 

0.001 0.01 0.1 1 10 100 1000 10,000 100,000 

STORAGE TRANSPORTATION 

SETTLING 

SAGGING / LEVELING 

APPLICATION 

Brookfield Shear Rate Range 

Rheometer Shear Rate Range 

PRODUCTION 

DISPERSION 

BRUSHING, ROLLING SPRAYING 

MIXING, STIRRING, PUMPING 

24

Proper Immersion of Brookfield Spindle 

1 

2 

1

Important Parameters to Control 

• Size of container 

• Depth of 

immersion 

• History of shear 

(especially for 

Thixotropic 

materials) 


FAST SLOW 

Velocity 

Gradient 

dv/dx 

• Spindle 

configuration 

• Rotational 

speed (rpm) 

• Time of shear 

(Helipath) 

• Temperature 

(25 o C) 

26

Brookfield Helipath Stand & T-Spindles 

(for very viscous liquids) 

Instruments control either shear rate or shear stress. A Brookfield viscometer is a 

controlled shear rate instrument. The shear stress is read off a scale while its motor is 

turning at a constant speed. Shear rate is controlled by spindle speed. Shear stress is 

controlled by spindle size and shape. 

27 

Cosmetic Division

Increasing Viscosity (Pa s) 

The inherent danger of a 1-point viscosity 

measurement instead of a rheogram 

QC – 1-point rotational viscometer measurement 

taken at a set shear rate (spindle speed in r.p.m.) 

X 

Increasing Shear Rate (s -1 ) 

Lot A Control 

Lot B

Increasing Viscosity (Pa s) 

The inherent danger of a 1-point viscosity 

measurement instead of a rheogram 

QC – 1-point rotational viscometer measurement 

taken at a set shear rate (spindle speed in r.p.m.) 

X 

Increasing Shear Rate (s -1 ) 

Lot A Control 

Lot B

Factors Effecting Settling Velocity 

Particle 

• count 

• size 

• shape 

• density 

• charge 

& Emulsion Stability 

Suspending Medium 

• density 

• charge 

• rheology 

• MW of suspending 

polymer

Stable Suspensions & Emulsions 

Yield Value 

Gravity 

Viscosity 

Adopted from “The Rheology of Natural and Synthetic Hydrophilic Polymer Solutions as related to Suspending Ability” By 

RJ Meyer and L. Cohen (BF Goodrich Chem. Co.) Presented in Nov. 1958, NYC. Published in Journal of cosmetic Chemists

Stokes Law 

predictor of emulsion stability 

V = 2r 2 g(D 1-D 2)/9µ 

Where: V = the particle’s settling velocity (m/s) 

r = the radius of the particle 

g = the gravitational acceleration (m/s 2 ) 

D1 = the density of the particles (kg/m 3 ) 

D2 = the density of the fluid (kg/m 3 ) 

µ = the viscosity of the fluid (Pa s) 

In words – A higher viscosity (denominator) 

reduces the settling velocity. Therefore, the 

emulsion or suspension will be more stable.

Insufficient force 

to induce flow 

Yield Value 

Enough force to overcome 

yield value of the toothpaste 

Yield Point (Pa) Viscosity (Pa·s) 

Honey 0 11.0 

Ketchup 14 0.1 

Mayonnaise 85 0.6

Brookfield Yield Value (BYV) 

BYV (dynes/cm 2 ) = (η1 - η2)/100 

BYV = (Apparent viscosity at 0.5 rpm – Apparent Viscosity at 1 rpm) 

BYV 

τ 1 

τ 2 

X 

100 

X 

r 1 r 2

Minimum BYV required for a stable suspension 

BYV = [23.6 R (D – D2) g] 2/3 

Where: R = particle radius (cm) 

D = density of particle (gm/cc) 

D2 = density of medium (gm/cc) 

g = acceleration due to gravity = 980 cm/sec 2 

Particle Volume = 4/3πR 3 

Cross Sectional Area = πR 2 


Gravity


Agenda 





36

Why use rheology modifiers? 

• Viscosity (Thickening) 

• Yield Value (Suspension) 

• Emulsion Stability (Stokes’ Law) 

• Flatten viscosity-temperature 

curve (consistency) 

• Product aesthetics (visual, etc.) 

• Dispensing & applying the product 

• Sensory perceptions (skin feel) 

• Even distribution of sunscreens 

(better coverage and skin 

protection) 

• Film-forming (styling and water 

resistance) 

• Homogeneity of actives 

• Prevent syneresis 

• Provide structural integrity to gels 

and solid stick forms 

• Leveling (nail polishes, 

sunscreens)

What are these Ingredients? 

• Viscosity Controlling Agents - 39 

– Silicones, Essential Oils, Sorbitol, Plant Extracts . . . 

• Viscosity Decreasing Agents - 101 

– Short chain Alcohols, Isoparaffins, Glycols, Ethoxylates . . . 

• Viscosity Increasing Agents 

– For Non-Aqueous Systems – 531 

• Waxes & long chain Alcohols, High MW Silicones, Alkylated 

Dimethicone . . . 

– For Aqueous Systems – 496 

• Alkanolamides, Betaines, Sodium Chloride, Polyquaternium 

Compounds . . .

Viscosity Increasing Agents 

• Long c-chain waxes with high melting 

points, electrolytes, perfumes, surfactants, 

acids & bases, higher solids content, etc. 

are typically not thought of as “rheology 

modifiers”. 

• So what is?

• Organoclays 

• Polyethylenes 


Non-Aqueous 

• Al/Mg Hydroxystearate 

• Trihydroxystearate 

• Polyethylene Glycols 

• Silicas 

• Synthetic Polymers 

Aqueous 

• Gums 

• Cellulosics 

• Clays 

• Polyethylene Glycols 

• Silicas 

• Synthetic Polymers


Viscosity Increasing Agents (Thickeners) 

• Naturally derived 

– Organic (plant or 

microbial) 

• Polysaccharides 

• Xanthan gum 

• Alginates 

• Cellulose 

• Guar gum 

– Inorganic 

• Smectite clays 

• Amorphous silicon 

dioxide 

• Synthetically derived 

– Polymers of Acrylic 

Acid (PAA) 

– Polyethylene and 

copolymers 

– Alkylene oxide polymers 

and esters 

– PVM/Decadiene 

Crosspolymer

Synthetic Polymeric Thickeners 

(Homopolymers, Copolymers, Crosspolymers) 

• Non-associative 

– Anionic – Carbomer, Acrylates Copolymer 

– Cationic – Polyquaternium-37 

• Associative 

– Anionic – Acrylates/Palmeth-25 Acrylate Copolymer, 

Acrylates/Steareth-20 Methacrylate Copolymer, Acrylates/C10- 

30 Alkylacrylate Crosspolymer . . . 

– Nonionic / Cationic – Acrylates/Aminoacrylates/C10-30 Alkyl 

PEG-20 Itaconate Copolymer, Polyacrylate-1 Crosspolymer 

(surfactant or acid swellable aqueous emulsion) . . .

Carbomer 

Anionic & Non-associative 

Polyacrylic Acid 

(PAA) 

Carbomer is a homopolymer of 

acrylic acid crosslinked with an 

allyl ether of either pentaerythritol, 

sucrose, or propylene. 

• Advantages of Carbomers: 

– Consistent quality, high purity & low 

toxicity 

– Low-use level, cost effective 

– Pseudoplastic rheology & good 

suspending power (yield value) 

– Wide pH application (4.5 – 11) 

• Other considerations of Carbomers: 

– Water phase thickeners 

– Require neutralization with suitable base 

– Incompatible with cationics 

– Poor electrolyte tolerance - recommend 

adding chelating agent (0.1% EDTA) 

– Photodegradable - recommend adding 

UV filter (0.1% Benzophenone-4) 

– Low emulsifying power 

– Very hygroscopic

Carbomer – Thickening Mechanism 

- COOH 

Dry Powder Dispersed Neutralized 

Tightly Coiled Loosely Coiled More Linear 

Swollen Hydrogels Tightly Packed 

Swollen Hydrogels 

Increasing Viscosity 

+ NaOH 

Na + 

- COO - 

Electrostatic repulsion

Controlling the rheology and 

performance of Carbomers 

• Solvent choice 

• Reaction parameters and drying time 

• Particle size 

• Extent of cross-linking 

• Molecular weight between crosslinks (Mc) 

• Polydispersity 

• Fraction of the total units, which occur as terminal, i.e. free 

chain ends 

• Surface treatment 

• Pre-neutralized INCI Name Sodium Carbomer 

• pH of the final formulation controls amount of swelling and 

packing


Carbomer Types 

(relative comparisons) 

Property Carbomer 

940/980 Types 

Carbomer 

941/980 Types 

Carbomer 934 

Type 

X-Linking High Low Medium 

Flow Characteristic Short Long Short 

Viscosity High Low Medium 

Yield Value Medium High Medium 

Electrolyte Tolerance Low Medium Medium 

Shear Tolerance High Low Medium 

Clarity Clear Clear Hazy 

46

USP/NF-29 

Classification of Residual Solvents by Risk Assessment 

• Class 1 – solvents to be avoided 

– Benzene is suspected carcinogen 

• Class 2 – solvents to be limited 

– Cyclohexane 

– Methylene Chloride (a.k.a. Dichloromethane) 

• Class 3 – solvents with low toxic potential. 

No exposure limit needed. 

– Ethyl Acetate 

– N-Heptane

US Pharmacopeia 

Official Monograph 

• Same names for Carbomers synthesized in Benzene - 

934, 940, 941 and 1342 (alkylated). All now prohibited 

in Europe. 

• New names for all Carbomers and alkylated 

Carbomers synthesized in a solvent other than 

Benzene became effective January 1, 2011. 

– Carbomer Homopolymer – PAA x-linked with allyl ethers of 

polyalcohols 

– Carbomer Copolymer – Co-PAA & long chain alkyl 

methacrylate x-linked with allyl ethers of polyalcohols 

– Carbomer Interpolymer - Carbomer Homopolymer or 

Copolymer that contains a block copolymer of polyethylene 

glycol and a long chain alkyl acid ester.

USP/NF-29 Carbomers 

• Carbomer Homopolymer 

– Homopolymer Type A = 4,000-11,000cps 

– Homopolymer Type B = 25,000-45,000cps 

– Homopolymer Type C = 40,000-60,000cps 

• Carbomer Copolymer 

– Carbomer Copolymer Type A = 4,500-13,500 

– Carbomer Copolymer Type B = 10,000-29,000 

– Carbomer Copolymer Type C = 25,000-45,000 

• Carbomer Interpolymer 

– Carbomer Interpolymer Type A = 45,000-65,000 

– Carbomer Interpolymer Type B = 47,000-77,000 

– Carbomer Interpolymer Type C = 8,500-16,500 

Type is determined by the viscosity range of a 0.5% Carbomer gel neutralized with NaOH 

using a Brookfield viscometer and appropriate spindle rotating at 20 rpm at 25 o C.

Carbomer Dispersion: EDUCTOR


Acrylates Copolymer 

Anionic and non-associative 

Acrylates Copolymer is a copolymer of two or more monomers 

consisting of Acrylic Acid, Methacrylic Acid or one of their 

simple esters. 

Acrylic Acid + Methacrylic Acid 

Ethylhexyl Acrylate 

51


Anionic and non-associative 

• Water-thin latex emulsion 

about 30% polymer solids 

• Some optimized to provide 

best clarity & peak viscosity / 

yield value at low pH 4.5-5.5 

required for Sodium 

Benzoate or Benzoic Acid 

efficacy 

• May require ‘back-acid 

titration’ step 

• Works synergistically with 

Alkanolamides and salt 

• Pseudoplastic with viscosity 

recovered after shear 


52


Polyquaternium-37 

Cationic & Non-associative 

Polyacrylic Acid 

Polymethacrylic Acid 

No 

Yes 

Synthesis of PQ-37 

Polyquaternium-37

Polyquaternium-37 

Cationic & Non-associative 

• Cationic thickener with high yield value 

• Available either as 100% high bulk density 

and low dusting powder or as a dispersion 

in Mineral Oil or Propylene Glycol 

Dicaprylate/Dicaprate 

• Self thickening – no neutralization required 

• Use-level 0.1-3.0% 

– 0.5% provide 7-13,000cps 

• Once dispersed in water can add up to 

70% EtOH 

• Compatible w/ iron oxides, sunscreens, & 

self tanners 

• Excellent water proofing film former with 

elegant skin-feel

Anionic Associative Thickeners 

• Acrylates/Palmeth-25 Acrylate Copolymer 

– 30% polymer solids latex emulsion 

• Acrylates/Palmeth-25 Itaconate Copolymer 

– 30% polymer solids latex emulsion 

• Acrylates/Vinyl Isodecanoate Crosspolymer 

– powder 

• Acrylates/C10-30 Alkylacrylate Crosspolymer 

• Acrylates/Beheneth-25 Methacrylate Copolymer

Anionic Associative Thickener 

INCI Name: Acrylates/Vinyl Isodecanoate Crosspolymer 

Hydrophilic part 

Thickening properties 

Lipophilic Part 

Emulsifying properties 

Resistance to electrolyte 

Sensorial improvement

HASE After Neutralization with Base 

Hydrophobic 

alkylation 

enhances 

performance 

in many 

systems 

Associative Polymeric Network 

Drawing courtesy of Raymond Rigoletto, Ashland Chemical 

HASE = 

Hydrophobically 

Modified 

Alkali 

Swellable 

Emulsion

Oil 

Action Mechanism 

Oil 

Oil 

Carbomer Alkylated Carbomer 

Oil 

Oil 

Oil

Anionic Associative Thickener 

Acrylates/Vinyl Isodecanoate Crosspolymer 

Mineral Oil (HLB 10) 

Up to 50% 

C12-15 Alkyl Benzoate (HLB 13) 

Up to 30% 

Caprylic/Capric Triglyceride (HLB 11) 

Up to 30% 

Cyclopentasiloxane (HLB 7.5) 

Up to 30%


Agenda 





60

Formula Considerations 

• Type of formula – gel, emulsion, foam, surfactant . . . 

• Desired rheology – viscosity, yield value . . . 

• Effect of pH 

• Electrolyte tolerance 

• Compatibility (charge characteristics) 

• Synergistic interactions 

• Processing parameters & filling equipment 

• Storage conditions (light, temperature) 

• Homogeneous delivery of active ingredients 

• Dispensing from packaging 

• Application to body 

• Skin feel


• Pseudoplastic 

– Synthetic Polymers: 

Polymers of Acrylic Acid, 

Carbomers, Hydrophobically 

Modifier Polymers 

– Gums: Guar, Hydroxypropyl 

Guar, Xanthan, Carrageenan 

– Clays: Hectorites, Bentonites, 

Mg/Al Silicates 

– Cellulosics: HEC, HPC 

– Silicas: Hydrated Silicas, 

Fumed Silicas 

• Newtonian 

– Polyethylene Glycols 

• Thixotropic 

– Gums: Karaya, 

Carrageenan 

– Organoclays: Quaternium- 

18 Hectorites & Bentonites, 

Stearalkonium Hectorites & 

Bentonites, 

Disteardimonium 

Hectorites 

– Polyethylenes 

– Silicas: Hydrated Silicas, 

Fumed Silicas 

– Trihydroxystearin 

– Al/Mg Hydroxystearate

Frequently used rheology modifiers 

in personal care formulations 

• Surfactant systems 

• Emulsions 

• Hair conditioners 

• Styling Mousse 

• Hair Styling Gels


Surfactant systems 

• PAA - Acrylates Copolymer, 

Acrylates/Palmeth-25 Acrylates Copolymer 

• Others - Salt, CAPB, Guar, Hydroxypropyl 

Methylcellulose, Xanthan Gum, PEG-150 

Distearate, Magnesium Aluminum Stearate, etc. 

• TIPS: improve lather stability, reduced salt 

raises surfactant cloud point, add fragrance prior 

to final pH & viscosity adjustments 

64

Carbomer and/or Acrylates/Vinyl Isodecanoate Crosspolymer 


Acrylates/Palmeth-25 Acrylates Copolymer 


65


Emulsions 

• PAA - Polymeric emulsifiers (associative 

thickeners), Carbomer, Hydrophobically 

Modified Carbomers 

• Others – Fatty Alcohols, Fatty Acids, 

Organoclays, etc. 

• TIPS: reducing surfactant emulsifiers often 

improves mildness and water resistance of 

sunscreens 

66


Hair conditioners 

• PAA - Polyquaternium-37, Polyacrylate-1 

Crosspolymer, etc. 

• Others - Fatty Alcohols, Hydroxyethyl Cellulose, 

etc. 

• TIPS: speed dissolution of HEC with heat and 

fully dissolve before adding other ingredients 

67


Hair Styling Mousse 

• PAA - Polyquaternium-37 

• Others - Cellulosics, Polyquaternium-4, 

Polyquaternium-10, Polyquaternium -24, PVP, 

etc. 

• TIPS: Foam should not become “too stable”, 

concentrate & propellant levels 

68

• PAA - Carbomer 


Hair Styling Gels 

• Others: Hydroxypropyl Cellulose. 

• TIPS: Partially neutralize Carbomer before 

adding PVP or PVP/VA to optimize clarity. Use 

EDTA Na 4 and Benzophenone-4. 

– Tetrasodium EDTA has pH >10.5 

– B-4 has pH

Special formulation challenges 

• Hydroalcoholic – selection of appropriate base is 

critical to successful thickening with Carbomers 

• Hydrogen peroxide – must keep pH below 5 for 

H 2O 2 stability 

• Sulfate-free and low WAS surfactant systems – 

NaCl just won’t do it 

• Sodium Benzoate, Benzoic Acid preservatives – 

require low pH for efficacy 

• Cationic – ionic charge incompatibilities 

• Oils – high processing temperatures and 

rheological properties. PAAs won’t thicken nonaqueous 

systems

Recommended Reading

Suggested Reading 

In print and available. Cost is 17,50 EU including Tax excluding Shipping. 

15 free copies if ordering 100 or more. 

Contact: Siegfried Fischer at s.fischer@sofw.com 

Tele: +49 82132583 16


Other References 

73

Suggested Reading on Rheology

Thank you 

Cosmetic Division

Formulating with Rheology Modifiers

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