Thermal Analysis of Polymeric Materials.pdf

Bernhard Wunderlich

Thermal Analysis of Polymeric Materials

Bernhard Wunderlich

Thermal Analysis

of Polymeric Materials

With 974 Figures

123

Prof. Dr. Bernhard Wunderlich

200 Baltusrol Road

Knoxville, TN 37922-3707

USA

wunderlich@chartertn.net

Library of Congress Controll Number: 2004114977

ISBN 3-540-23629-5 Springer Berlin Heidelberg New York

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Preface

Thermal analysis is an old technique. It has been neglected to some degree because

developments of convenient methods of measurement have been slow and teaching

of the understanding of the basics of thermal analysis is often wanting. Flexible,

linear macromolecules , also not as accurately simply called polymers, make up the

final, third, class of molecules which only was identified in 1920. Polymers have

never been fully integrated into the disciplines of science and engineering. This book

is designed to teach thermal analysis and the understanding of all materials, flexible

macromolecules, as well as those of the small molecules and rigid macromolecules.

The macroscopic tool of inquiry is thermal analysis, and the results are linked to

microscopic molecular structure and motion.

Measurements of heat and mass are the two roots of quantitative science. The

macroscopic heat is connected to the microscopic atomic motion , while the

macroscopic mass is linked to the microscopic atomic structure . The macroscopic

units of measurement of heat and mass are the joule and the gram, chosen to be easily

discernable by the human senses. The microscopic units of motion and structure are

the picosecond (10 12 seconds) and the ångstrom (10 10 meters), chosen to fit the

atomic scales. One notes a factor of 10,000 between the two atomic units when

expressed in “human” units, second and gram—with one gram being equal to one

cubic centimeter when considering water. Perhaps this is the reason for the much

better understanding and greater interest in the structure of materials, being closer to

human experience when compared to molecular motion.

In the 19 th century the description of materials could be based for the first time on

an experiment-based atomic theory. This permitted an easy recognition of the

differences between phases and molecules . Phases are macroscopic, homogeneous

volumes of matter, separated from other phases by well-defined boundaries, and

molecules are the constituent smallest particles that make up the phases. As research

progressed, microphases were discovered, initially in the form of colloidal

dispersions. More recently, it was recognized that phase-areas may be of nanometer

dimensions (nanophases). On the other hand, flexible macromolecules have

micrometer lengths or larger. Particularly the nanophases may then have structures

with interfaces that frequently intersect macromolecules, giving the materials unique

properties.

Finally, the classical phases, gases, liquids, and solids, were found to be in need

of expansion to include mesophases and plasmas. The discussion of history in the

first lecture shows the tortuous path scientific discovery takes to reach the present-day

knowledge. Easier ways can be suggested in hindsight and it is vital to find such

simpler approaches so to help the novice in learning. In this book on “Thermal

Analysis of Polymeric Materials” an effort is made to discover such an easy road to

understand the large, flexible molecules and the small phases, and to connect them

to the small molecules and macroscopic phases which are known for much longer.

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Preface

Since the goal of this book is to connect the new knowledge about materials to the

classical topics, but its size should be restricted to two to three semesters’ worth of

learning, several of the standard classical texts were surveyed by the author. Only

when a topic needed special treatment for the inclusion of thermal analysis or macro-

molecules, was this topic selected for a more detailed discussion in this book. The

knowledge in polymer science, in turn, often improves the understanding of the other

types of molecules. A typical example is discussed in the first lecture when

describing the classification-scheme of molecules. With this approach, the learning

of materials science, as a whole, may be less confusing. A series of six additional

examples of such improvement of the understanding is given on pg. VII.

The study of “Thermal Analysis of Polymeric Materials” is designed to

accomplish two goals: First, the learning of the new subject matter, and second, to

stimulate a review of the classical topics. Naturally, one hopes that in the future all

topics are included in the main educational track. This joining of the physics,

chemistry, and engineering of small and large molecules with thermal analysis is of

urgency since most students must in their career handle polymeric materials and deal

with the application of some type of thermal analysis. A list of short summaries of

the seven chapters of the book is given below for a general orientation and to allow

for reading, starting at different entry points:

Chapter 1 Atoms, Small, and Large Molecules is designed to enhance the understanding

and history of the development of knowledge about small and large molecules. Furthermore,

the nomenclature, description, and characterization of linear macromolecules by basic theory

and experiment are summarized.

Chapter 2 Basics of Thermal Analysis contains definitions of systems, flux, and

production and the following thermodynamic functions of state which are needed for the

description of thermal analysis results: heat capacity, enthalpy, entropy, and free enthalpy.

Chapter 3 Dynamics of Chemical and Phase Changes is a summary of the syntheses by

matrix, stepwise, step, and chain reactions. It also contains information on emulsion

polymerizations, cross-linking, gelation, copolymerization, and decomposition. Kinetics of

nucleation, crystallization, and melting, as well as glass transitions are chosen as representative

of the dynamics of phase changes.

Chapter 4 Thermal Analysis Tools contains a detailed description of thermometry,

calorimetry, temperature-modulated calorimetry (TMC), dilatometry, thermomechanical

analysis (TMA), dynamic mechanical analysis (DMA), and thermogravimetry (TGA).

Chapter 5 Structure and Properties of Materials covers the solid states (glasses and

crystals), mesophases (liquid, plastic, and condis crystals), and liquids. Also treated are multi-

phase materials, macroconformations, morphologies, defects and the prediction of mechanical

and thermal properties.

Chapter 6 Single Component Materials provides detailed descriptions of phase diagrams

with melting, disordering, and glass transitions. In addition, the effects of size, defects, strain

on transitions and properties of rigid amorphous and other intermediate phases are treated in

the light of thermal and mechanical histories.

Chapter 7 Multiple Component Materials , finally covers our limited knowledge of

chemical potentials of blends, solutions, and copolymers. The Flory-Huggins equation, phase

diagrams, solvent, solute, and copolymer effects on the glass, melting, and mesophase

transitions are the major topics.

This book grew out of the two three-credit courses “Physical Chemistry of

Polymers” and “Thermal Analysis” at The University of Tennessee, Knoxville

(UTK). First, the lectures were illustrated with overhead foils, generated by

computer, so that printouts could be provided as study material. In 1990 these

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