Surfactants in Agrochemicals

285 Pages·2018·9.23 MB·English

by  Tharwat F. Tadros

SURFACTANTS
IN
AGROCHEMICALS
SURFACTANT SCIENCE SERIES
CONSULTING EDITORS
MARTIN J. SCHICK FREDER/CK M. FOWKES
Consultant (1915-1990)
New York, New York
1. Nonienie Surfactants, edited by Martin J. Schick (see also Volumes 19
and 231
2. Solvent Properties of Surfactant Solutions, edited by Kozo Shinoda (out
of printl
3. Surfactant Biodegradation, R. D. Swisher (see Volume 181
4. Cationic Surfactants, edited by Eric Jungermann (see also Vol u mes 34,
37, and 531
5. Detergency: Theory and Test Methods (in three partsl, edited by W. G.
Gutler and R. C. Davis (see also Volume 201
6. Emulsions and Emulsion Technology (in three parts), edited by Kenneth
J. Lissant
7. Anionic Surfactants (in t wo parts), edited by Warner M. Linfield (out of
printl
8. Anionic Surfactants: Chemical Analysis, edited by John Cross (out of
printl
9. Stabilization of Colloidal Dispersions by Polymer Adsorption, Tatsuo
Sato and Richard Ruch
1 O. Anionic Surfactants: Biochemistry, Toxicology, Dermatolog y, edited by
Christian Gloxhuber (see Volume 431
11. Anionic Surfactants: Physical Chemistry of Surfactant Action, edited
by E. H. Lucassen-Reynders (out of printl
12. Amphoteric Surfactants, edited by B. R. Bluestein and Clifford L. Hilton
(out of printl
13. Demulsification: lndustrial Applications, Kenneth J. Lissant
14. Surfactants in Textile Processing, Arved Datyner
15. Electrical Phenomena at lnterfaces: Fundamentals, Measurements, and
Applications, edited by Ayao Kitahara and Akira Watanabe
16. Surfactants in Cosmetics, edited by Martin M. Rieger
17. lnterfacial Phenomena: Equilibrium and Dynamic Effects, Clarence A.
Miller and P. Neogi
18. Surfactant Biodegradation: Second Edition, Revised and Expanded, R.
D. Swisher
19. Nonionic Surfactants: Chemical Analysis, edited by John Cross
20. Detergency: Theory and Technology, edited by W. Gate Gutler and Erik
Kissa
21. lnterfacial Phenomena in Apolar Media, edited by Hans-Friedrich Eicke
and Geoffrey D. Partitt
22. Surfactant Solutions: New Methods of lnvestigation, edited by Raoul
Z ana
23. Nonionic Surfactants: Physical Chemistry, edited by Martin J. Schick
24. Microemulsion Systems, edited by Henri L. Rosana and Marc Clausse
25. Biosurfactants and Biotechnology, edited by Naim Kosaric, W. L.
Cairns, and Neil C. C. Gray
26. Surfactants in Emerging Technologies, edited by Milton J. Rosen
27. Reagents in Mineral Technology, edited by P. Somasundaran and Brij
M. Moudgil
28. Surfactants in ChemicaiiProcess Engineering, edited by Darsh T.
Wasan, Martin E. Ginn, and Dinesh O. Shah
29. Thin Liquid Films, edited by l. B. lvanov
30. Microemulsions and Related Systems: Formulation, Solvency, and
Physical Properties, edited by Maurice Bourrel and Robert S. Schecter
31. Crystallization and Polymorphism of Fats and Fatty Acids, edited by
Nissim Garti and Kiyotaka Sato
32. lnterfacial Phenomena in Coal Technology, edited by Gregory D.
Botsaris and Yuli M. Glazman
33. Surfactant-Based Separation Processes, edited by John F. Scamehorn
and Jeffrey H. Harweil
34. Cationic Surfactants: Organic Chemistry, edited by James M.
Richmond
35. Alkylene Oxides and Their Polymers, F. E. Bailey, Jr., and Joseph V.
K oleske
36. lnterfacial Phenomena in Petroleum Recovery, edited by Norman R.
Morrow
37. Cationic Surfactants: Physical Chemistry, edited by Donn N. Rubingh
and Paul M. Holland
38. Kinetics and Catalysis in Microheterogeneous Systems, edited by M.
Grätzel and K. Kalyanasundaram
39. lnterfacial Phenomena in Biological Systems, edited by Max Bender
40. Analysis of Surfactants, Thomas M. Schmitt
41. Light Scattering by Liquid Surfaces and Complementary Techniques,
edited by Dominique Langevin
42. Polymeric Surfactants, Irja Piirma
43. Anionic Surfactants: Biochemistry, Toxicology, Dermatolog y. Seco n d
Edition, Revised and Expanded, edited by Christian Gloxhuber and
Klaus Kunstler
44. Organized Solutions: Surfactants in Science and Technology, edited by
Stig E. Friberg and Björn Lindman
45. Defoaming: Theory and lndustrial Applications, edited by P. R. Garrett
46. Mixed Surfactant Systems, edited by Keizo Ogina and Masahiko Abe
4 7. Coagulation and Flocculation: Theory and Applications, edited by
Bohuslav Dob1äs
48. Biosurfactants: Productian · Properties · Applications, edited by Naim
Kosaric
49. Wettability, edited by John C. Berg
50. Fluorinated Surfactants: Synthesis · Properties · Applications, Erik
Kissa
51. Surface and Colloid Chemistry in Advanced Ceramics Processing,
edited by Robert J. Pugh and Lennart Bergström
52. Technological Applications of Dispersions, edited by Robert B. McKay
53. Cationic Surfactants: Analytical and Biological Evaluation, edited by
John Cross and Edward J. Singer
54. Surfactants in Agrochemicals, Tharwat F. Tadros
ADDITIONAL VOLUMES IN PREPARATION
Solubilization in Surfactant Aggregates, edited by Sherril D. Christian
and John F. Scamehorn
SURFACTANTS
IN
AGROCHEMICALS
Tharwat F. Tadros
Zeneca Agrochemica/s
Berkshire, England
0
CRC Press
Taylor & Francis Group
Boca Ra ton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
Library of Congress Cataloging-in-Publication Data
Tadros, Th. F.
Surfactants in agrochemicals l Tharwat F. Tadros.
p. cm. - (Surfactant science series ; 54)
lncludes bibliographical references and index.
ISBN 0-8247-9100-2 (hardcover)
l. Surface active agents. 2. Agrkultural chemicals-Adjuv
ants. I. Title. II. Series: Surfactant science series ; v. 54.
S587.73.S95T33 1994
668' .6-dc20 94-37159
CIP
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Preface
Surfactants play a major role in agrochemicals in both formulatian
and optimization of biological efficacy. To formulate an y agrochemi
cal as a dispersion or dispersible system that is suitable and economic
for application, one needs to use a suitable surfactant. Surfactants are
essential for the preparation of any disperse system, such as an oil/
water emulsion, a suspension concentrate, and a microemulsion. Sur
factants are also essential for maintaining the long-term physical sta
bility of these systems and their application as sprays. Dispersible
systems such as wettable powders, emulsifiable concentrates, and
water-dispersible grains also require surfactants for their application.
In all formulations, the surfactant plays a crucial role in enhancing
and optimizing the biological efficacy of agrochemicals. Indeed, with
many agrochemicals, a high concentration of surfactant may be re
quired for ensuring the efficacy of the chemical.
In spi te of the above obvious ro les of surfactants in agrochemicals,
fundamental studies of their role in formulatian preparation, and op
timization of biological efficacy are, to date, far from satisfactory.
iii
iv Preface
Most formulation chemists choose their surfactants using trial and
error. As a result, each time a new agrochemical is discovered the
formulation chemist repeats this tedious procedure to find the most
suitable surfactant. This is particularly the case for discovering the
surfactant that gives optimal biological efficacy.
This book has been written with the objective of introducing a
fundamental approach to the selection of surfactants in agrochemical
formulations. After a short general introduction (Chapter 1) to illus
trate the role of surfactants in various agrochemicals formulations,
Chapter 2 is devoted to the physical chemistry of surfactant solutions.
This fundamental chapter summarizes the unusual properties of sur
factant solutions, in particular their micellization and the formation of
structural units as spherical, rod shaped, and lameBar systems, which
play a major ro le in biological efficacy. Chapter 3 deals with the
adsorption of surfactants and polymers (sometimes referred to as
macromolecular surfactants) at the air/liquid, liquid/liquid, and solid/
liquid interfaces. This subject is essential for understanding how sur
factants and polymers can stabilize disperse systems such as emul
sions, suspensions and microemulsions.
Chapter 4 deals with the subject of emulsifiable concentrates,
which lack fundamental understanding for their formulation. An ex
ample is given to illustrate how a fundamental approach may be used
to understand the formation of these systems and their spontaneity of
emulsification on dilution. Chapter 5 presents a great deal of funda
mental knowledge on the preparation and subsequent stabilization of
emulsions. Suspension concentrates are similarly described in Chapter
6. A potentially useful type of formulation is a microemulsion which
to date has seldom been used in the agrochemical industry. The ad van
tages of microemulsions over emulsions are their inherent thermo
dynamic stability and their potential to enhance biological efficacy;
this topic is covered in some detail in Chapter 7. The last chapter
discusses the role of surfactants in transfer and performance of agro
chemicals. This is perhaps the most difficult subject to deal with at a
fundamental level. However, an attempt has been made to describe
the role of surfactants in spray droplet formation and in wetting and
spreading, as weil as their impaction adhesion and retention. The role
Preface v
of surfactants in deposit formation, solubilization, and their effect on
transport is briefly described to illustrate how surfactants may enhance
the biological efficacy of an agrochemical.
It should be mentioned that this text is far from exhaustive. I have
concentraled on topics on which I have carried out some fundamental
research.
Since this book was written at home in my spare time, in particular
during Christmas vacations, I am indebted to my wife and children
for their tolerance of my sp ending the time writing rather than enjoying
various activities with them.
Tharwat F. Tadros