Table Of ContentPOLYMERIC FOAMS SERIES
series editor S.T. Lee
THERMOPLASTIC
FOAM
PROCESSING
Principles and Development
© 2005 by CRC Press LLC
POLYMERIC FOAMS SERIES
series editor S.T. Lee
INCLUDED TITLES
Polymeric Foams: Mechanisms and Materials
S. T. Lee and N.S. Ramesh
Thermoplastic Foam Processing: Principles and Development
Richard Gendron
© 2005 by CRC Press LLC
POLYMERIC FOAMS SERIES
series editor S.T. Lee
THERMOPLASTIC
FOAM
PROCESSING
Principles and Development
Edited by
Richard Gendron
CRC PR ESS
Boca Raton London New York Washington, D.C.
© 2005 by CRC Press LLC
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Library of Congress Cataloging-in-Publication Data
Thermoplastic foam processing : principles and development / edited by Richard Gendron.
p. cm. — (Polymeric foams series)
Includes bibliographical references and index.
ISBN 0-8493-1701-0 (alk. paper)
1. Thermoforming. 2. Plastics—Extrusion. I. Gendron, Richard. II. Series.
TP1151.T48T44 2004
668.4'93—dc22
2004051966
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Dedication
To Ariane and Corinne, my beloved daughters,
and to all of my collaborators’ children,
with the hope that the world we are building for them
is a much, much better one.
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Foreword
Even though polymer foams have been around for about half a century, a
body of scientific literature that could have provided a better understanding
of foam processing has only become available recently. But why does one
need that kind of understanding? Being part of the industrial community, I
have lived, along with my colleagues, with the traditional trial and error
system for years and have gotten results. Well, the problem is that the
outcome resulting from such a system is uncertain. How much time, effort,
and money have we spent before getting valuable results? How many prof-
itable opportunities have we lost?
In 1993, I came to visit the National Research Council’s Industrial Materials
Institute (IMI). I brought my industrial experience and some expertise in
process development, but more importantly, I had many questions in mind:
• What makes a blowing agent work and how does it interact with
the polymer?
• How is the viscosity of the blowing agent–polymer mixture affected,
and can it be measured, instead of guessing at it by using some
fudge factors?
• Under what conditions do bubbles start to form during the foaming
process?
• Could I use this information to improve processing equipment, and
especially to improve the design of mixers and extrusion dies?
At that time, despite their long experience in polymer extrusion and com-
pounding, foaming was not part of the IMI researchers’ preoccupations, so
no definitive answers were given to any of these questions. However, being
truly motivated by that challenging process, the National Research Council
initiated a decade of collaboration with the foam industry, which led for
instance to the creation of the FoamTech technology group and to a much
more valuable and unique concentration of expertise in the foam area.
Being one of the early industrial partners who introduced polymer foam
processing and its problematics to this research team, I am very pleased also
to introduce this book. It summarizes the acquired knowledge of a group of
dedicated researchers who became devoted over the last 10 years of hard
work to the study of polymer foaming, through exploratory works or in
collaboration with the scientific and industrial community engaged in this
field.
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Foam practitioners involved in production, research, or development will
not necessarily find in this book straightforward solutions to their daily
problems or specific answers to their long-lasting questions. They will find,
instead, practical tools, valuable facts, and a basic understanding of many
aspects of the foaming process that will indubitably help them to develop
innovative solutions to many practical problems.
Louis Michel Caron
Vice President – Technologies
Valotech, Inc.
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Preface
On September 25, 1996, at the Industrial Materials Institute (IMI) of the
National Research Council of Canada (NRC), the FoamTech technology
group was officially launched, and its first meeting, regrouping people from
the foam industry and research and development (R&D) specialists, was
kicked off. Responding to industrial preoccupations focused on seeking
replacements for banned ozone-depleting foaming agents, a multidiscipli-
nary research team was set up to provide its industrial partners with scien-
tific expertise and access to the experimental facilities available in the
institutes involved in this program. In addition to IMI, the Institute for
Research in Construction (IRC) and the Institute for Chemical Processes and
Environmental Technology (ICPET) were part of the task force that was
initiated.
The core activities of the R&D program were developed in accordance
with the needs expressed at that time. It became rapidly apparent that new
foaming formulations and better mechanical properties, as well as a fine
understanding of the rheology underlying the foam extrusion process, would
be the top priorities for the NRC researchers involved in the FoamTech
program. Obviously, development and validation of innovative physical
foaming agent and polymer combinations would require accurate informa-
tion about solubility and diffusivity and a clearer understanding of the
mechanisms involved during foaming (nucleation and growth), especially
when they occur under the practical conditions experienced during produc-
tion. In-line monitoring, performed with noninvasive techniques, was iden-
tified as a valuable complement to the data generated off-line. The research
should highlight the contribution of viscoelasticity to concerns previously
addressed through thermodynamic principles only. Some research activities
conducted at IMI have focused on the development of characterization meth-
ods suitable to the thermoplastic foam extrusion process. Examples of
research conducted over the years include the development of a novel in-
line monitoring technique based on ultrasonic sensors. The technique has
provided a better understanding of the dynamics of phase separation in
terms of the key parameters that govern the formation of bubbles. Another
example is the use of an on-line rheometer directly installed on the extrusion
line, permitting the characterization of the rheological behavior of the poly-
mer–blowing agent mixture. These essential measurements were tradition-
ally difficult to achieve, the volatility of the blowing agents preventing the
use of traditional off-line rheometers.
The relevance of the work conducted by NRC researchers, which has
contributed to improving on a continuous basis their expertise in this
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domain, was validated by the reputation of their industrial partners.
Leistritz, 3M, Dow, Owens-Corning, Sealed Air, AtoFina, and Pactiv are some
of the first and longest-lasting members that supported and benefited over
the years from the work accomplished in NRC laboratories.
The topics developed in this book are intimately associated with the core
activities undertaken since the creation of the foam-related research program
at IMI. They reflect, therefore, past issues that have been addressed by the
NRC specialists at some time, and also unanswered questions that still persist
despite our laborious efforts. This book does not pretend to provide all the
answers to problems formulated during the last 10 years, although it may
suggest interesting paths that belong to the actual research inquiry. This book
was written by experts of two kinds: Dr. Jekyll supplied the rigorous aca-
demic background, while Mr. Hyde shared experience in his favorite
playground, filled with large-scale processing equipment. These experimen-
tations were addressed with practical concerns in mind, as the NRC research-
ers interacted closely with the field practitioners. Nevertheless, part of their
preoccupation in writing the manuscript was to provide the reader with
useful tools that could be relevant for foam development and, moreover, to
suggest fresh and innovative ideas that would still need dedicated efforts to
be explored. These ideas should provide potential work for the next
10 years…
© 2005 by CRC Press LLC
