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4 Rheological Properties of Newtonian Polymeric Materials Filled with Microparticles

5.3.3 Comparison between Dynamic-Mechanical and Creep and Creep-Recovery Experiments

5.3.6 Extension of the Frequency Range of Dynamic-Mechanical Experiments by Retardation Spectra

5.3.10 Influence of the Molecular Structure of the Matrix on Rheological Properties of Silica-Filled Polymers

6.1.4 Comparison of the Effect of Carbon Black on the Storage Modulus and the Electrical Conductivity

6.3.2 Rheological Properties of Polymethylmethacrylate Filled with Multiwall Nanotubes

6.3.3 Rheological Properties of Polypropylene Filled with Multiwall Carbon Nanotubes

8.2.1 Elongational Viscosity of a Low-Density Polyethylene Filled with Various Particles

8.2.3 Elongational Viscosity of a Low-Density Polyethylene Filled with Glass Beads

9 Rheological Behavior of Polymer Melts with Intrinsic Structural Heterogeneities

9.2 Rheological Properties of Polycarbonate and Their Relation to Internal Structures

9.2.2 Rheological Behavior as a Function of Time for Various Polycarbonate Samples

10.4.2 Composites of PMMA and Multiwall Carbon Nanotubes Prepared by Solution Mixing

14.1 Rheological Properties of Various Acrylonitrile-Butadiene-Styrene Copolymers

14.2 Rheological Properties of Acrylonitrile-Styrene-Acrylicester Copolymers (ASA)

14.4 Models for Particle Interactions in Rubber-Filled Styrene-Acrylonitrile Copolymers

17.2 Morphology Development in Newtonian Liquids under Simple Shear and Planar Extension

19.6 Determination of the Anisotropy of Particle Distributions by X-ray Diffraction

Helmut Münstedt

Rheological and
Morphological Properties
of Dispersed Polymeric
Materials

Filled Polymers and Polymer Blends

1st Edition

The author:

Prof. Dr. Helmut Münstedt, Institute of Polymer Materials, Friedrich-Alexander-University Erlangen-Nürnberg, Martensstr. 7, D-91058 Erlangen, Germany; E-mail: helmut.muenstedt@fau.de

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The idea of this book, “Rheological and Morphological Properties of Dispersed Polymeric Materials,” came up during my work, together with F. R. Schwarzl, on our book, “Deformation and Flow of Polymeric Materials,” published in 2014. Writing the manuscript, we found that we had to restrict ourselves to homogeneous polymer melts in order to keep the volume at a reasonable size. It is obvious, however, that flow properties of heterogeneous polymeric systems are of interest from two points of view. First, materials of that kind play an important role in practice as filled polymers and polymer blends. Their rheological behavior is the basis for an assessment of processing. In addition to the molecular structure as in the case of homogeneous melts, the heterogeneous components may build up morphological features that affect various properties. Second, it is challenging from a more fundamental aspect to find out what can be learned from rheological properties with respect to interactions between fillers and matrix molecules and those between the heterogeneous phases themselves.

Another interesting topic is the different nature of the heterogeneous phases used: rigid particles in filled polymeric materials and deformable organic phases in polymer blends. In particular, the latter ones offer a wide scope for variation and, consequently, lead to a variety of physical effects. However, an understanding of properties of heterogeneous materials is not possible without a comprehensive knowledge of the morphological development. This is different, of course, for polymers filled with particles and polymer blends. Especially interesting from a fundamental point of view and, therefore, particularly suited to educate students in the field of rheology are comparisons of the different properties of heterogeneous phases with respect to their influences on the rheological behavior. On the other hand, morphologies can be generated or changed under the influence of flow fields in the molten state. The interplay between morphology and rheology is an interesting field of research with respect to fundamental insights and applications.

Investigations of this kind on polymeric materials have been scarce in the literature and that was the reason why, over the years, research has been performed at the Institute of Polymer Materials of the Friedrich-Alexander-University Erlangen-Nuremberg. The results of diploma and doctoral theses gradually became actual parts of the lectures for students in advanced phases of their studies. This book contains some teaching topics and, therefore, may be particularly suited for students interested in the interaction of rheological and morphological features of heterogeneous systems. Moreover, the book is thought to offer an introduction to dispersed polymers and provide valuable information for those working in research, development, and application of these materials.

By using measurements on well-defined samples it is shown how the introduction of a second phase to a polymer matrix changes rheological properties. As far as possible, the underlying mechanisms are explained, leading the reader to a broader understanding and a knowledge-based assessment of the influence of a dispersed phase on the rheological behavior. In the case of polymer blends, the interplay between morphology changes and flow patterns is a key point that is elucidated.

Several doctoral works and publications that resulted from them became the basis of this book. The investigations on polyisobutylene with various glass beads and on polymethylmethacrylate with nanoparticles were so comprehensive that my former doctoral students Michael Schmidt and Christian Triebel are coauthors of the corresponding Chapters 4 and 5. Markus Heindl as doctoral student and Zdenek Stary as senior researcher at the Institute performed many investigations on the morphology development within polymer blends under elongation. That is the reason why they are coauthors of the corresponding Chapter 17. Moreover, Zdenek Stary was the initiator of the work on compatibilized blends and most of the investigations were performed under his guidance. Therefore, he coauthors the presentations in this field described in Chapter 18.

Some readers may criticize the relatively small numbers of references on each topic. But since the book is based on many in-house results, it seemed to be an appropriate way to cite the original works that contain, of course, further literature relating to the special field. The easy access to various data bases and electronic bibliographies today allows the reader of the book to go more into details according to his or her needs and interests.

However, some experimental information, which is very special and not easily available from general sources, is given in one appendix to the particle-filled polymeric materials (Chapter 10) and in another to polymer blends (Chapter 19). The appendices are intended to guide those readers who are interested in details of the experiments. Furthermore, some results of the investigations are described in the appendices that lie somewhat outside the main topics of the book, but present interesting data with some potential for applications.

Special acknowledgement goes to the former doctoral students of mine whose results from the theses they performed under my supervision have been used in this book: Dr. Marcus Heindl, Dr. Jens Hepperle, Dr. Nikolaos Katsikis, Dr. Ute M. Kessner, Dr. Andreas Kirchberger, Dr. Michael Schmidt, and Dr. Christian Triebel. I am grateful for their permission to use results from their works beyond the publications in scientific journals.

Additionally, the coauthors of some chapters, Dr. Marcus Heindl, Dr. Michael Schmidt, Dr. Zdenek Stary, and Dr. Christian Triebel, are thanked for many fruitful discussions and their proof reading.

The comments of Privatdozent Dr. Ulrich A. Handge on the rheological properties of particle-filled polymeric materials and immiscible and compatibilized blends, particularly from the doctoral thesis of Dr. Christian Sailer working under his guidance, are gratefully acknowledged. Discussions with Prof. Dr. Florian J. Stadler are also appreciated.

The experimental results forming the core of this book would not have been possible without the consistently high engagement of the technicians of the Institute of Polymer Materials and the motivated work of many diploma and master students. In particular, results from the diploma or master theses of Tobias Königer, Thomas Köppl, and Johannes A. Krückel are appreciated who have become PhDs in the meantime. Last but not least, M.Sc. Andrea Dörnhöfer, M.Sc. Alexander Heitbrink, and M.Sc. Ute Zeitler supported me in getting the many figures ready. All of them are thanked for their skillful assistance.

Special thanks go to Cheryl Hamilton from the Hanser Publishing Company who edited the manuscript with great care and competence.

Erlangen, June 2016

Helmut Münstedt

Dispersed organic systems are ubiquitous in nature. Wood consisting of lignin and cellulose is a well-known example. A natural dispersion is blood that consists of plasma and dispersed organic cells. The main ingredient of the plasma is water and, therefore, its flow behavior is Newtonian. The organic cells of various shapes and compositions are distributed in the plasma and significantly influence the flow properties of blood.

Many of our food products consist of different ingredients not miscible with each other. Their flow properties play an important role either during processing or consumption. An example is dough whose main ingredients are a liquid like water or milk and dispersed flour particles. Dough is an extremely complicated material regarding its flow properties. Another example is chocolate, for which the flow behavior of a dispersed system plays a certain role for its production and for generating special tastes when eaten.

From daily life one knows toothpaste as a dispersed material that flows differently according to the forces applied: It is capable of being easily pressed out of a tube, but nearly rigid on the brush. Common particle-filled materials are paints and lacquers, printing inks, and cosmetic articles, for example. A special feature of these flowable systems is a low viscosity under load and a high one at rest. A dispersed material used in huge amounts worldwide is concrete, whose flow properties can become important when transported by pumping.

It should be mentioned that the dispersed component of a system can also be a gas or another liquid. The first composition is typical of foams, for the second, oily ingredients in water; milk, soaps, and creams are good examples.

All these materials are dispersions generally defined as mixtures of various ingredients that are not soluble with each other. Solid particles dispersed in a fluidic medium are called suspensions, immiscible liquids form an emulsion, and a system of liquid or solid particles in a gaseous medium is designated as an aerosol.

The matrices of most of these materials that form the base component of a dispersion have a low Newtonian viscosity, particularly in the case of water, which is often used as dispersing medium. A lot of investigations have already been performed on dispersions based on water. Much less is known, however, on the flow properties of filled systems with matrices of higher viscosities than water or even of a non-Newtonian behavior. Such systems play an important role in the case of polymers that have found wide applications as engineering materials over the last decades. The products available on the market are numerous today. A great variety of organic and inorganic fillers mixed into various types of polymeric materials are in use. The fillers serve to improve properties of the matrices or to generate features the basic materials do not possess.

Another way of modifying existing products is blending them together to get new characteristics superior to those found for the components. Because only very few polymers are miscible with each other, most of the blends show a heterogeneous structure and can be considered as a dispersion in which both matrix and heterogeneous phase are of a polymeric nature. Such blends currently represent a big market in the field of engineering polymers.

Inherent to dispersed polymeric materials is the fact that optimizing one property by changing the composition alters other properties. This interplay has widely been investigated with respect to characteristics of the solid state, because they are interesting for applications. However, much less can be found in the literature on rheological properties, however, that may significantly be influenced by a component added to a matrix. Because the rheological behavior is a key factor for processing, it has to be balanced with respect to other material features required.

Nevertheless, the number of rheological textbooks in the field of dispersed polymeric materials is rather small. In one book, discussions on the rheology of polymer blends [1.1] are found, others are concerned with the rheology of filled polymers [1.2], [1.3]. Common books on rheology either do not deal with dispersed polymeric materials at all or only cover limited aspects, for example, [1.4], [1.5], [1.6].

The economic importance of filled polymeric materials and polymer blends and the very significant role that rheological properties play in their processing led to the conception of this book. Its main topics are related to polymers as the matrix that exhibit distinctly higher viscosities than water and are non-Newtonian in many cases. The discussion of particle-filled materials and polymer blends together in one volume offers the challenging chance to point out the similarities and differences of these two systems.

Besides rheological characterizations with respect to the different deformations and stresses occurring during processing, the other aspects dealt with are how rheological investigations can be used to get insight into interactions between structural heterogeneities themselves or interactions with matrix molecules. Another interesting field discussed in this book is the use of rheological measurements to follow up on morphological changes. Furthermore, the role of special flow fields in the molten state is elucidated for the generation of droplet distributions in polymer blends.

	[1.1] Utracki L. A., Polymer Alloys and Blends, Hanser Verlag, Munich, Germany (1989)
	[1.2] Shenoy A. V., Rheology of Filled Polymer Systems, Kluwer Academic Publishers, Berlin, Germany (1999)
	[1.3] Leblanc H., Filled polymers: science and industrial applications, CRC Press, Boca Raton, Florida (2010)
	[1.4] Vinogradov G. V., Malkin A.Ya., Rheology of Polymers, Springer Verlag, Berlin, Germany (1980)
	[1.5] Macosko C. W., Rheology: Principles, Measurements, and Applications, Wiley-VCH, Weinheim, Germany (1994)
	[1.6] Münstedt H., Schwarzl F. R., Deformation and Flow of Polymeric Materials, Springer, Berlin, Germany (2014)

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