Rheology

1. Part 1
Practical Rheology
Contents
Page
1. Introduction 2
2. Special Characteristics of Dispersions
And Emulsions 6
3. Three Schools of Rheological Thinking 9
4. Thinking Rheo-logically 12
5. Definitions 14
6. Types of Flow Behavior 19
7. Characterization of Non-Newtonian Flow: 27
Mathematical Models and Experimental
Methods
8. Viscometry; Instrumentation and Use 49
9. Summary 64
10. Symbols and Abbreviations 65
11. References 67
1

2. 2 Rheology Modifier Handbook
1. Introduction
In the first section of Part 1 we introduce the basics of Practical
Rheology. This includes examples of products and processes that
employ rheological measurement as well as a concise summary of
ASTM viscosity test procedures describing the characterization of a
broad range of materials.
The second section of Part 1 describes the more common types of flow
behavior. This includes methods for measuring rheological properties
and describing complex flow behavior with a minimum of useful
parameters. The use of such tools and techniques allows rheological
measurement to be used as an effective tool for the characterization of a
broad range of industrial fluids. The discussion concludes with a
description of several of the more common viscometers.
Appendix A contains a partial listing of viscometer manufacturers and
contact information as well as some of the viscometric instruments they
manufacture.
A wide variety of useful industrial products and processes require tailor-
made flow properties as an integral part of product performance
requirements. Effective control of such properties relies heavily on a
knowledge of the effect of formulation and process variables as well as
an ability to measure and characterize meaningful flow property
information. Rheology modifiers play a significant role in achieving
desirable flow characteristics and this handbook describes the properties
of all the major types as well as their practical use and application.
Examples of some of the wide variety of products and processes which
rely on rheological characterization include food products,
pharmaceuticals, biological fluids and a host of miscellaneous materials.
In the food category, rheological phenomena are important for tomato
juice, dehydrated potato granules, soft serve ice milk and
microcrystalline cellulose thickeners. Also included in this category are
single cell protein concentrates, milk coagulation, chocolate, dressings
and sauces. In the biological area, work has been done on blood, serum,
exocrine secretions, sweat, duodenal fluid and synovial fluid.

3. Practical Rheology 3
Among the many miscellaneous applications for rheology we find
asphalts, hevea latex, aerated poultry waste and livestock slurry
characterization. The list continues with color cosmetics, lubricants, clay
gellants, black liquor (paper processing) and ceramics. Also included are
one-fire glazes, enamel slips, thick film ceramic pastes and dental
impression materials. Other examples include solder paste, molten glass,
high titanium oxide slags and blast furnace slags. Coconut oil liquid
soaps are also characterized rheologically as well as vinyl plastisols,
urethane foam prepolymers, inks, paper coatings, high solids coatings
and solvent based coatings.
The American Society of Testing Materials (ASTM) has provided
standards of control and testing for many years. The use of Practical
Rheology is clearly evident in the breadth and scope of the kinds of
products and processes which benefit from rheological characterization.
One of the authors is a member of several standards-making committees
and is well apprised of the wide variety of industry specialists involved
in setting up useful, working standards. While the individual reader of
this work may be specifically focused upon a certain industry, or type of
product, the authors feel that a succinct overview of the kinds of
materials which have benefited will be of value in setting the stage for
generating a powerful view of what Practical Rheology is and can be.
In the Petroleum field the ASTM provides tests for testing of rubberized
tar (D 2994-77), and coal tar (D 1665, D 1669-51 and D 5018-89). In the
heavy petroleum end there are tests for unfilled asphalts (D 4402-87),
asphalt emulsion resins (D 4957-95) and asphalt roof coatings (D 4479).
Other rheological tests in the asphalt area include D 2170, D 3205,
D 3791-90, D 244, D 2161 and D 4957. Bitumen rheology tests for non-
Newtonian systems are described in D 4957. Testing of lubricating
greases (D 3232-88), aircraft turbine lubricants (D 2532-93) and engine
oils (D4684) are also covered as well as roofing bitumens in D 4989-90.
ASTM has tests for hydrocarbon oils such as fuel oil pumpability
(D 3245), lubricating oils (D 2270) and engine oils (D 5133 and D 5293).
Testing of hydraulic fluids is described in D 6080 and automotive fluid
lubricants are tested in D 2983-87. Oil standards are described in
D 2162.

4. 4 Rheology Modifier Handbook
Rubber testing in the carbon black industry is conducted using D 4483,
rubber latexes in D 5605 and D 1417. SBR latexes are covered in D
3346 and prevulcanized rubber testing in D 1646. Ammonia-preserved
(concentrated) creamed and centrifuged natural rubber latex testing is
described in D 1076-88 while rheological testing of synthetic rubber
latexes is described in D 1417-90.
The field of polymers has numerous ASTM tests for characterization and
control. Some of these include tests for Hydroxyethylcellulose (D 2364-
85), Ethylcellulose (D 914-72), Sodium Carboxymethylcellulose (D
1439-83), and Hydroxypropylcellulose (D 5400-93). Hydroxypropyl-
methylcellulose testing is shown in both D 3346-90 and D 2363.
Polymer-containing fluid testing is described in D 3945 while tests for
polyols are shown in D 4989-91. Polyethylene terephthalate rheology
testing is described in D 4603-96 and epoxy resin evaluation is described
in D 2393-86. Polyamide rheology testing is covered in D 789.
Common products such as chemical grouts are evaluated rheologically in
D 4016-81 as are printing inks and their vehicles (D 4040-96), grout for
pre-placed aggregate concrete (C 939-87) and glass, above its softening
point (C 965-81).
Paint testing is covered in D 1084-88 and D 562-81. Varnishes for
electrical testing are described in D 115-85 and emulsion polymers for
floor polishes are covered in D-3716-83. Liquid-applied neoprene and
chlorosulfonated polyethylene in roofing water proofing is described in
D 3468-93.
Adhesives testing is available in D 1084-88 and D 4300-83. Testing of
hot melt adhesives is described in D 3236-88 and hot melts made from
petroleum waxes with additives are covered in D 2669-87. Mold powder
testing above the melting point is shown in C 1276.
Miscellaneous rheological testing is available from the ASTM for tall oil
(D 803), clear liquids (D 1545), crude or modified isocyanates for
polyurethanes (D 4889-93), volatile and reactive liquids (D 4486-91) and
plastisols and organosols (D 1823 and D 1824). Still other ASTM
rheology tests exist for solid propellants, starch and solder paste.

5. Practical Rheology 5
Having reviewed the host of rheological testing described by the ASTM.
One can see the great value of rheology evaluation across a broad
spectrum of industries. We turn our attention now to the use of rheology
in the cosmetic and toiletry industry. Most of the products on the market
today in this market are emulsions (either of the oil-in-water or water-in-
oil types), aqueous suspensions or a combination of the two. Many skin
care creams and lotions are oil-in-water emulsions, while liquid makeup
formulations are suspensions of pigments in an oil-in-water emulsion.
Antidandruff shampoos are usually suspensions. Certain organosilicones
are highly effective dispersants for pigments used in color cosmetics.