From the Preface This book is the first extended look at a new and
multifaceted polymer processing technology that has already been
discussed in numerous articles. Called Solid-State Shear
Pulverization (S3P), this innovative process produces polymeric
powders with unique physical properties not found in the output of
conventional size-reduction methods.... This technology, which
utilizes a pulverizer based on a modified co-rotating twin-screw
extruder..., has profound implications for both the creation of new
polymer blends and recycling of plastic and rubber waste. Unlike
[earlier processes] where polymers are melted prior to
pulverization, ...pulverizing mixtures of polymers with the S3P
process...does not involve melting. By contrast, S3P maintains
polymers in the solid state and avoids the additional heat history
that occurs during [other processes], which can be detrimental to
the physical properties of pulverized materials. The research and
development of the S3P technology...has grown significantly since
1990 from the development of a new plastics recycling process to a
much broader polymer processing method that allows intimate mixing
of polymers with very different viscosities, sold-state dispersion
of additives, including pigments, and continuous production of
powder with unique shapes and larger surface areas. Polymeric
powders are of growing importance to plastics processors due to the
increase use of plastics in various applications, such as
rotational molding, powder coatings, and compounding, which require
powder as the feedstock. ...[I]t has become clear that this process
allows for in-situ compatibilization of dissimilar polymers by
applying mechanical energy to cause chemical reactions. This aspect
of S3P technology that we describe in this book should [be useful
in] developing new polymer blends with the use of pre-made
compatibilizing agents. In addition, it has been discovered that
S3P efficiently mixes polymer blends with different component
viscosities, resulting in the elimination of phase inversion. The
S3P process directly produces blends with matrix and dispersed
phase morphology like those obtained after phase inversion during a
long melt-mixing process. This phenomenon is of practical
importance because a long processing time is required by
conventional melt-mixing to produce a stable blend morphology. S3P
is also advantageous for producing thermoplastic or thermoset
powder-coating compounds in a one-step process as opposed to a
conventional multi-step operation that involves melt extrusion
followed by batch grinding. The major capabilities of this new
process can be summarized as follows: o Continuous powder
production from plastics or rubber feedstocks o Blending of
immiscible polymers o Efficient mixing of polymers with unmatched
viscosities o Environmentally friendly recycling of multicolored,
commingled plastics waste o Sold-state dispersion of heat-sensitive
additives o Engineered plastic/rubber blends Materials and
processes well illustrated The text is well illustrated with 60
photographs, micrographs, diagrams and others figures. Here is a
small sampling of the captions of these figures. o Particle-size
distribution for virgin LDPE powder made with PT-25 pulverizer o
Optical photograph of virgin LDPE powder made with PT-25 pulverizer
o Layout for a three-stage rubber pulverizer o Flow chart for
powder coating production by conventional process and with new S3P
technology o SEM image of pulverized virgin PP at 40X (first in
series of SEM images of polymer powders) o Optical micrograph of
melt-crystallized thin films of unpulverized virgin PP under
polarized light o Log of viscosity vs. log shear rate for virgin
HDPE after S3P processing o Gel permeation chromatograms (GPC) of
polystyrene subjected to S3P processing Color-photo section One of
the several functions of Solid-State Shear Pulverization technology
is recycling mixed plastic waste. This section of twenty full-color
photographs and micrographs illustrates different processed
materials, as well as the machinery and mixed waste used. Here is a
small sampling of the photo and micrograph captions. o Resultant
flake feedstock from granulation o S3P-made uniform powder from
feedstock o Flake feedstock of post-consumer HDPE/PP blend (90/10
ratio) o Injection-molded test bar (with translucence) made from
S3P powder without pelletization o Injection-molded test bar made
from S3P powder without pelletization showing uniform color o
Several test bars subjected to tensile testing showing
exceptionally high elongation at break Useful reference data in
tables More than 60 tables provide useful data in convenient form.
Here is a small sampling of table captions. o Physical properties
of virgin PP 8020 GU injection-molded from S3P-made powder (first
in series of tables on physical properties of various plastics
processed from S3P-made powder) o Sieve analysis of powder
resulting from S3P of virgin LDPE 509.48 (one of series of tables
on sieve analysis of polymer powders) o Melt-flow rate before and
after S3P processing for virgin PS and two PP samples o Key
physical properties of injection-molded post-consumer polyolefin
blends pulverized by S3P process The Authors Klementina Khait, M.S.
Ch.E., Ph.D., is Research Associate Professor and Director of the
Polymer Technology Center in the Department of Chemical
Engineering, Northwestern University. Her industrial experience in
polymer science and engineering includes work with Borg-Warner
Chemicals and Quantum Chemical Corporation. She received her two
advanced degrees, in chemical engineering and polymer chemistry,
from the Technological Institute, St. Petersburg, Russia. Dr. Khait
holds several patents and has published more than 50 papers in
scientific and technical journals. Stephen Carr, Ph.D., is
Professor of Materials Science and Engineering and Chemical
Engineering at Northwestern University. His industrial work
includes work in polymer science and engineering with General
Motors Corp. He received a doctorate in polymer science from Case
Western Reserve University. He has been on the Northwestern
University faculty since 1969. Martin H. Mack is Vice President for
R&D with the Berstorff Division of Krauss-Maffei Corporation.
He holds an engineering degree from the University of Stuttgart. He
has served for more than ten years on the Board of Directors of the
Society of Plastics Engineers (SPE).
General
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