Rheology Modifiers Handbook - Practical Use and Application

502 Pages·2000·5.98 MB·English

by  Braun

RHEOLOGY
MODIFIERS
HANDBOOK
Practical Use and Application
by
David B. Braun Meyer R. Rosen
Interactive Consulting Inc.
East Norwich, New York
William Andrew Publishing
Norwich, New York, USA
Copyright by William Andrew Publishing
Llbrary of Congress Catalog Card Number: 99-32076
ISBN: 0-8155-1441-7
Prlnted In the United States
Published In the United States of America by
Willlam Andrew Publishing
13 Eaton Avenue, Norwich, New York 13815
10987654321
Library of Congress Cataloging-in-Publication Data
Rheology modifiers handbook: practical use & application / by David B. Braun and
Meyer R. Rosen.
p. cm.
Includes bibliographical references and index.
ISBN 0-8155-1441-7
1. Rheology. I. Rosen, Meyer R. II. Title.
TP156.R45 B73 2000
660’ .29--dc21 99-32076
CIP CIP
Preface

Rhe(cid:149)ol(cid:149)o(cid:149)gy \rēēēē----!!!!(cid:228)(cid:228)(cid:228)(cid:228)----lllləəəə----jjjjēēēē\\\\ n : a science dealing with the
deformation and flow of matter (fluids in this text)

Merriam Webster(cid:146)s Collegiate Dictionary, 10th Edition

Rheology Modifier : A material that alters the rheology
of fluid compositions to which it is added

Authors

Rheology modifiers seem to be almost as ubiquitous as plastics. Most of
us regularly consume them in the food and pharmaceuticals we use.
Cosmetic creams, lotions, nail polish and liquid make-up also usually
contain rheology modifiers to achieve proper application characteristics.
We clean our kitchens, baths, floors and automobiles with products that
frequently contain these important ingredients. Even the paint we apply
to walls and woodwork contains these useful additives. These are only a
few of the applications of rheology modifiers.

They may be multi-functional agents in these applications, providing
such desirable effects as viscosity, the ability to suspend insoluble
ingredients, emulsion stability, anti-sag and vertical surface cling, for
example.

During our lengthy careers in the Research and Development
Departments of major chemical companies, we were frequently
confronted with the need to select a rheology modifier for use in the
application we were working on. This was invariably a long, arduous
task requiring review of the technical literature of numerous suppliers of
rheology modifiers to determine which types of products would be
suitable for the application. This was followed by contact with those
companies that supplied the desired products to obtain their latest
technical literature and product recommendations. Finally, we would
pare the list of potential candidates from hundreds to perhaps a few
dozen.

vii
But we often wondered why there existed no rheology modifier
sourcebook, i.e., a single volume that would enable me to easily identify
the best candidates for the application with a minimum investment of
time. This handbook is our attempt to correct that deficiency. Our goal is
to bring together, in one volume, the information that a researcher needs
to select the best rheology modifier candidates for his/her project,
whether it is a food, pharmaceutical, cosmetic or household/industrial
application. It includes information on twenty different chemical types of
rheology modifiers, from acrylic polymers to xanthan gum,
manufactured by twenty-six chemical companies around the world.
This handbook is divided into four major parts:

Part I reviews of the basic concepts of rheology and its measurement
from a practical standpoint. This is information the researcher needs to
compare the performance of various rheology modifiers in the intended
application.

Part II presents details about the many commercial products of each
chemical type that are available from the twenty-six companies
represented in this book. The products are arranged alphabetically, first
by chemical type, then by supplier(cid:146)s name and finally by trade name. An
attempt has also been made to differentiate products in a given product
line. Over 1000 commercial products are included in this Part.

Part III focuses on the important step of selecting the most suitable
rheology modifier candidates. It summarizes the applications for which
each type of rheology modifier is recommended so that the user of this
handbook can immediately identify which types are recommended for
the intended application. It also covers regulatory issues that the user
should be familiar with when choosing a product for use in a food or
pharmaceutical application. At this point, it is prudent for the user to
contact the suppliers of the best candidates to get their recommendation
for the products in their line which are the most suitable for the intended
application.

viii
Part IV is a formulary containing the contributions of the product
suppliers. These 227 starting formulations are arranged by industry;
food, pharmaceutical, cosmetic and household/industrial. They are
designed to show which rheology modifiers are recommended for
various applications and how they are normally incorporated into a
formulation.

Following these four major parts, are three appendixes that provide the
names, addresses, telephone and FAX numbers, Internet Web Page
locations and E-mail addresses for the suppliers of rheological
instruments and suppliers of rheology modifiers represented in this book.
Also appended is a trade name directory indicating the owners of trade
names that appear in this handbook.

The authors hope this book will enable researchers to reduce the time
required to select the best rheology modifiers for an intended application
from a matter of days to a matter of hours.

David B. Braun
Meyer R. Rosen

ix
Contents
Page
Part 1 Practical Rheology
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

Part 2 Commercially Available Rheology Modifiers
Introduction 71
1. Acrylic Polymers 74
2. Cross-linked Acrylic Polymers 81
3. Alginates 89
4. Associative Thickeners 94
5. Carrageenan 99
6. Microcrystalline Cellulose 106
7. Carboxymethylcellulose Sodium 109
8. Hydroxyethylcellulose 114
9. Hydroxypropylcellulose 119
10. Hydroxypropylmethylcellulose 121
11. Methylcellulose 128
12. Guar & Guar Derivatives 132
13. Locust Bean Gum 138
14. Organoclay 141

v
Part 2 Commercially Available Rheology Modifiers Page
15. Polyethylene 151
16. Polyethylene Oxide 157
17. Polyvinyl Pyrrolidone 161
18. Silica 167
19. Water-swellable Clay 174
20. Xanthan Gum 184

Part 3 Selecting the Best Candidates
Introduction 194
1. For Food Applications 199
2. For Pharmaceutical Applications 213
3. For Personal Care Applications 222
4. For Household/Institutional Applications 243

Part 4 Formulary
Introduction 259
1. Food Formulations 261
2. Pharmaceutical Formulations 297
3. Personal Care Formulations 340
4. Household/Institutional Formulations 425

Appendix A Suppliers of Viscometers and Other Rheological
Instruments 489

Appendix B Trade Name Directory 498

Appendix C Suppliers of Rheology Modifiers 502

vi
6 Rheology Modifier Handbook
2. Special Characteristics
of
Dispersions and Emulsions

The following quote is reprinted by permission of Brookfield
Engineering Laboratories from Section 4.7.4 of it(cid:146)s technical manual(53),
More Solutions to Sticky Problems- A Guide to Getting More from Your
Brookfield Viscometer. This manual has had worldwide distribution for
over 20 years and has become a standard in the industry. Meyer R.
Rosen, the co-author of this handbook, was a contributing author to this
Brookfield Manual.

(cid:147)Dispersions and emulsions, which are multiphase materials consisting
of one or more solid phases dispersed in a liquid phase, can be affected
rheologically by a number of factors. In addition to many of these
discussed previously, characteristics peculiar to multiphase materials are
also significant to the rheology of such materials.

One of the major parameters to study is the state of aggregation of the
sample material. Are the particles that make up the solid phase separate
and distinct or are they clumped together; how large are the clumps and
how tightly are they stuck together? If the clumps (i.e. flocs) occupy a
large volume in the dispersion, the viscosity of the dispersion will tend to
be higher than if the floc volume was smaller. This is due to the greater
force required to dissipate the solid component of the dispersion.

When flocs are aggregated in a dispersion, the reaction of the aggregates
to shear can result in shear-thinning (pseudoplastic) flow. At low shear
rates, the aggregates may be deformed but remain essentially intact. As
the shear rate is increased, the aggregates may be broken down into
individual flocs, decreasing friction and therefore, viscosity.

If the bonds within the aggregates are extremely strong, the system may
display a yield value. The magnitude of the yield value depends on the
force required to break these bonds and is often critical in suspending
materials within the formulation.

If a material(cid:146)s flocculated structure is destroyed with time as it is
sheared, a time-dependent type of flow behavior will be observed. If the
Practical Rheology 7
shear rate is decreased after some or all of the flocculated structure is
disrupted, the material(cid:146)s viscosity may be lower than it previously was at
the same shear rate. Since flocs begin to link together after destruction,
the rate at which this occurs affects the time required for viscosity to
attain previous levels. If the re-linking rate is high, viscosity will be
about the same as before. If the re-linking rate is low, viscosity will be
lower. This results in the rheological behavior called (cid:145)Thixotropy(cid:146).

The attraction between particles in a dispersed phase is largely dependent
on the type of material present at the interface between the dispersed
phase and the liquid phase. This in turn affects the rheological behavior
of the system. Thus, the introduction of flocculating or deflocculating
agents into a system is one method of controlling its rheology.

The shape of the particles making up the dispersed phase is also of
significance in determining a system(cid:146)s rheology. Particles suspended in
a flowing medium are constantly being rotated. If the particles are
essentially spherical, rotation can occur freely. If, however, the particles
are needle- or plate-shaped, the ease with which rotation can occur is less
predictable, as is the effect of varying shear rates.

The stability of a dispersed phase is particularly critical when measuring
the viscosity of a multiphase system. If the dispersed phase has a
tendency to settle, producing a non-homogeneous fluid, the rheological
characteristics of the system will change. In most cases, this means that
the measured viscosity will decrease. Data acquired during such
conditions will usually be erroneous, necessitating special precautions to
ensure that the dispersed phase remains in suspension.(cid:148) (53)

The cosmetic chemist is faced with the formidable task of combining a
number of different cosmetic ingredients (frequently ten or more) to form
a stable composition with the desired flow characteristics, application
properties and aesthetics. Having accomplished the task in the
laboratory, it must then be scaled up to production sized batches without
losing any of the desired performance characteristics. Thereafter, the
product quality must be controlled to ensure that each production batch is
the same.(57)
8 Rheology Modifier Handbook
It is common practice to measure the viscosity of a cosmetic composition
and use this property as a quality control parameter. A single viscosity
measurement at a single shear rate (or spindle speed if using a Brookfield
Viscometer) does not provide adequate definition of the rheology of the
composition. This is because the cosmetic product is exposed to a broad
spectrum of shear fields during preparation, packaging and eventual use
by the consumer. For example, the use of a centrifugal pump to transport
the product from the mixing tank to the packaging station involves
exposure to high shear inside the pump. The act of pouring the
composition from the container is a low shear process, but spreading the
product on the skin involves high shear. Since many cosmetic
suspensions and emulsions display pseudoplastic rheology, it is
important to measure and control the viscosity over a range of shear
rates.

In order to address the issues described above, the flow properties of
such materials may be described both qualitatively and quantitatively.
Although the mathematics of rheology can be extremely complex, a
qualitative appreciation for these phenomena may be gained by
observing some common materials. For example, toothpaste acts like a
liquid when the tube is squeezed, but acts like a solid when squeezing
ceases. Some paints flow onto a wall easily but do not drip from a brush
or flow down the wall. Initial stirring of a latex paint can be difficult, but
will become easier as stirring continues. On cessation of stirring, the
paint thickens with passing time.

Qualitative observations such as those above can be quite useful for
describing the great variety of flow properties typically encountered.
However, to those concerned with producing and controlling such
properties, a more quantitative approach is necessary.

According to Section 1.3 of reference (53), (cid:147)there are three schools of
thought on viscosity measurement(cid:148). We present them here and invite
you to decide which you belong to, remembering that there is no (cid:147)right(cid:148)
one and that each school has its merits at certain times.