High-Temperature Properties and Applications of Polymeric Materials

259 Pages·1995·21.3 MB·English

by  Martin R. Tant

ACS SYMPOSIUM SERIES 603
High-Temperature Properties
and Applications of Polymeric
Materials
1
0
0
w
3.f
60 Martin R. Tant, EDITOR
0
95- Eastman Chemical Company
9
1
k-
b
1/
102 John W. Connell, EDITOR
0.
oi: 1 National Aeronautics and Space Administration
s.org 995 | d
s.ac3, 1 Hugh L. N. McManus, EDITOR
b1
http://puOctober Massachusetts Institute of Technology
2 | e:
201Dat
August 19, Publication Dbeyv tehloe pDeidv firsioomn o af s Pymolypmoseiurimc Mspaotnersoiarlesd:
Science and Engineering, Inc.,
at the 207th National Meeting
of the American Chemical Society,
San Diego, California,
March 13-17, 1994
American Chemical Society, Washington, DC 1995
In High-Temperature Properties and Applications of Polymeric Materials; Tant, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
Library of Congress Cataloging-in-Publication Data
High-temperature properties and applications of polymeric materials /
Martin R. Tant, editor, John W. Connell, editor, Hugh L. N. McManus,
editor.
p. cm.—(ACS symposium series; 603)
"Developed from a symposium sponsored by the Division of Polymeric
Materials: Science and Engineering, Inc., at the 207th National Meeting
of the American Chemical Society, San Diego, California, March 13-17,
1994."
1
0
0 Includes bibliographical references and indexes.
w
3.f ISBN 0-8412-3313-6
0
6
0
5- 1. Polymers—Thermal properties. 2. Polymeric composites—Thermal
99 properties.
1
k-
b I. Tant, Martin R., 1953- . II. Connell, John W., 1959- .
21/ III. McManus, Hugh L. N., 1958- . IV. American Chemical Society.
10 Meeting (207th: 1994: San Diego, Calif.) V. American Chemical
0. Society. Division of Polymeric Materials: Science and Engineering.
1
oi: VI. Series.
s.org 995 | d T62A0.415 5'9.P205482H956—8 d1c92905 95-33341
s.ac3, 1 CIP
b1
http://puOctober This book is printed on acid-free, recycled paper.
2 | e:
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In High-Temperature Properties and Applications of Polymeric Materials; Tant, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
1995 Advisory Board
ACS Symposium Series
Robert J. Alaimo Cynthia A. Maryanoff
Procter & Gamble Pharmaceuticals R. W. Johnson Pharmaceutical
Research Institute
Mark Arnold
University of Iowa Roger A. Minear
1
0 University of Illinois
0
w David Baker at Urbana-Champaign
03.f University of Tennessee
6
0 Omkaram Nalamasu
5-
9 Arindam Bose AT&T Bell Laboratories
9
k-1 Pfizer Central Research
1/b Vincent Pecoraro
02 Robert F. Brady, Jr. University of Michigan
1
0. Naval Research Laboratory
1
oi: George W. Roberts
s.org 995 | d MChaermy EEd.i t CCaosmteplalnioyn North Carolina State University
bs.ac13, 1 Margaret A. Cavanaugh JUonhivne rRsit. yS ohfa Iplllienyoi s
http://puOctober National Science Foundation at Urbana-Champaign
2 | e: Arthur B. Ellis Douglas A. Smith
201Dat University of Wisconsin at Madison Concurrent Technologies Corporation
August 19, Publication GUnuinvedras itIy. oGf Keoarngsa s LD.u PSoonmt asundaram

Madeleine M. Joullie Michael D. Taylor
University of Pennsylvania Parke-Davis Pharmaceutical Research
Lawrence P. Klemann William C. Walker
Nabisco Foods Group DuPont
Douglas R. Lloyd Peter Willett
The University of Texas at Austin University of Sheffield (England)
In High-Temperature Properties and Applications of Polymeric Materials; Tant, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
Foreword
IHE ACS SYMPOSIUM SERIES was first published in 1974 to
provide a mechanism for publishing symposia quickly in book
form. The purpose of this series is to publish comprehensive
books developed from symposia, which are usually "snapshots
1
0 in time" of the current research being done on a topic, plus
0
w
3.f some review material on the topic. For this reason, it is neces
60 sary that the papers be published as quickly as possible.
0
5- Before a symposium-based book is put under contract, the
9
19 proposed table of contents is reviewed for appropriateness to
k-
b the topic and for comprehensiveness of the collection. Some
1/
02 papers are excluded at this point, and others are added to
1
0. round out the scope of the volume. In addition, a draft of each
1
oi: paper is peer-reviewed prior to final acceptance or rejection.
s.org 995 | d Terhsi)s oafn othney msyomusp orseivuimew, wphroo cbeessc oims es uthpee revdisiteodr (bsy) othf et heo rbgaonoikz.
s.ac3, 1 The authors then revise their papers according to the recom
b1
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2 | e: who check that all necessary revisions have been made.
201Dat As a rule, only original research papers and original re
August 19, Publication vtiioenws poaf pperresv iaorues liyn pcluubdliesdh iend tphaep evrosl uamre ens.o t Vaecrcbeapttiemd. reproduc

In High-Temperature Properties and Applications of Polymeric Materials; Tant, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
Preface
HIGH-TEMPERATURE-HIGH-PERFORMANCE ORGANIC POLYMERS and
polymer composites are materials that exhibit superior properties, in
terms of both thermal and mechanical behavior, to those of more typical
materials. These properties include stability at high temperatures (tens of
thousands of hours at 350 °F in air), light weight (low density), high
specific strength and stiffness, high toughness, low heat distortion and
1 warpage, and good processability.
0
pr0 The maturation of the field of synthetic polymer chemistry, as well as
3. the development of an improved understanding of structure-property
0
6
0 relationships, has resulted in the ability to synthesize materials with prop
5-
99 erties designed for a particular application. This versatility makes these
1
k- high-temperature-high-performance organic polymers attractive for
b
1/ aerospace, microelectronic, and other industrial applications. Current
2
0
1 uses include films in semiconductor applications, matrix resins in carbon
0.
oi: 1 fiber reinforced composites, foams for insulation, ablatives, adhesives for
d metals and composites, fibers for sporting goods, and membranes for
s.org 995 | industrial gas separation.
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12 | ate: chapter designed to give an overview of the entire field. The remainder
0D
9, 2on of book is organized into three sections: Properties; Processing and
st 1cati Modeling; and Applications and New Materials. Each section contains
gubli four to six chapters describing leading edge research and development
uu
AP that encompass a variety of materials, experimental techniques, theories,

processes, and applications. Work is included from an international
group of scientists and engineers from the United States, Canada, France,
Italy, and Australia.
The breadth of the information presented in this book should make it
useful for materials scientists, polymer chemists, and engineers in the
aerospace, automotive, chemical, and electronics industries. We hope
that the book will become a useful resource for a broad spectrum of
scientists and engineers whose work concerns the preparation, processing,
properties, and applications of polymers and polymer composites.
vii
In High-Temperature Properties and Applications of Polymeric Materials; Tant, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
Acknowledgments
Several organizations generously provided funds to support the sympo
sium upon which this book is based. We thank Eastman Chemical Com
pany, Netzsch, AMETEK— Haveg Division, the Petroleum Research
Fund of the American Chemical Society, and the ACS Division of Poly
meric Materials: Science and Engineering, Inc.
We very much appreciate the help of Anne Wilson and Rhonda Bit-
terli of the ACS Books Department who managed to keep both the edi
tors and contributors on track. Finally, we thank the contributors for
sharing the results of their work with us.
MARTIN R. TANT
Research Laboratories
01 Eastman Chemical Company
0
pr Kingsport, TN 37662
3.
0
6
0
5- JOHN W. CONNELL
9
19 Langley Research Center
k-
b National Aeronautics and Space Administration
1/
02 Hampton, VA 23681-0001
1
0.
1
oi: HUGH L. N. MCMANUS
d
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bs.a13, Cambridge, MA 02139
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viii
In High-Temperature Properties and Applications of Polymeric Materials; Tant, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
Chapter 1
High-Temperature Properties and Applications
of Polymeric Materials
An Overview
Martin R. Tant1, Hugh L. N. McManus2, and Martin E. Rogers1
1Research Laboratories, Eastman Chemical Company, P.O. Box 1972,
Kingsport, TN 37662
2Technology Laboratory for Advanced Composites, Department
of Aeronautics and Astronautics, Massachusetts Institute
1
0 of Technology, Cambridge, MA 02139
0
h
c
03. In this chapter we present an overview of the high-temperature
6
5-0 properties and applications of polymers and polymer composites.
99 Included are discussions of heat transfer in polymer-based
1
k- materials, their physical and mechanical properties at elevated
b
1/ temperatures, chemical and physical aging of polymers and effects
2
10 of aging on properties, and the thermal and mechanical response in
0.
1 high-temperature, high-heat-flux environments. Finally, we present
oi: a brief discussion of modern high-temperature polymers and the
d
s.org 995 | effect of molecular structure on their properties.
c1
s.a3, Polymeric materials have long been utilized in high-temperature and high-heat-flux
b1
puer environments. From the natural rubbers first utilized in internal combustion engines
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012 | Date: met the high-performance challenge presented by the design engineer. Much of the
9, 2on credit for this success is due to the maturation of the field of synthetic polymer
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the improved understanding of relationships between polymer structure, both molecular
and morphological, and the physical and mechanical properties of these materials.
Advances in modeling of high-temperature heat transfer in polymers have aided in the
understanding of how polymers react to extreme environments. Finally, advances
made in processing of high-performance polymers and their composites continue to
trigger improvements in their performance in critical applications.
In this introductory chapter, we present a broad overview of the field of high-
temperature properties of polymers and polymer composites. We begin by considering
the basic principles of heat transfer in polymer-based materials. The thermophysical
properties of these materials relative to their performance in thermal environments are
then discussed. The thermomechanical behavior of polymers is then addressed,
0097-6156/95/0603-0001$12.00/0
© 1995 American Chemical Society
In High-Temperature Properties and Applications of Polymeric Materials; Tant, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
2 HIGH-TEMPERATURE PROPERTIES AND APPLICATIONS OF POLYMERS
followed by brief discussions of chemical and physical aging during service and the
potential influence of aging on physical and mechanical properties. Having thus
established a fundamental understanding of the important aspects of heat transfer and
thermophysical properties of polymers, we then describe important aspects of their
response in moderately high temperature service and then in extreme environments.
Finally, we give a brief overview of the chemistry of modern polymers developed
specifically for use in high-performance, high-temperature applications.
Mechanisms of Heat Transfer in Polymers and Polymer Composites
Heat transfer in solid, liquid, and gaseous media occurs by conduction, convection, and
radiation. The mechanism of overwhelming importance in non-decomposing polymer-
based materials is conduction. Fourier's law of one-dimensional, steady-state heat
1
0 conduction in an isotropic medium is given as
0
h
c
3.
0 (1)
6
0
5-
9
9
1
bk- where q is the heat flux in the χ direction resulting from the temperature gradient
21/ dT/dx, and k is the thermal conductivity. For composites, the thermal conductivity is
0
0.1 generally anisotropic, and this must be considered in heat conduction problems. Heat
1
oi: transfer within a thermally decomposing polymer also occurs by convection or flow
d of decomposition gases within the material. Though radiant heat transfer within a
s.org 995 | polymer or polymer composite is negligible, radiant heat transfer between the material
s.ac3, 1 and its surroundings may indeed be important. This problem is well described in
b1 standard heat transfer treatises (7,2).
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012 | Date: q = h(T- TB) (2)
9, 2on
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the concept of the convective heat transfer coefficient (and thus the Nusselt number)
cannot be applied to dissipative flows such as flowing polymer melts. This is
illustrated by the fact that for highly dissipative flows the convective heat transfer
coefficient may actually turn out to be negative, which, of course, is physically
meaningless. Winter uses the Biot number (often used for the thermal boundary
condition for solids) for polymer melts.
The energy equation is general and describes energy conservation in any
material or process. It is given by
DU
= -(V«g) -Ρ(ν·ν) - (x:Vv) + S (3)
pDt
where D/Dt is the substantial derivative, defined by
In High-Temperature Properties and Applications of Polymeric Materials; Tant, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
1. TANT ET AL. An Overview 3
(4)
and V is the differential operator
V=8 (5)
1 dx1 2 dx2 3 3x3 "
U is the specific internal energy (per unit mass), ρ is the density, t is time, and q is
the heat flux vector. The single term on the left side of equation (3) represents the
rate of internal energy gain per unit volume. The term -(ν·^) is the rate of internal
energy input by conduction per unit volume. The term -P(Vev) is the reversible rate
1 of internai energy increase per unit volume by compression, and the term -(x:Vv) is
0
0
h the irreversible rate of internal energy increase per unit volume by viscous dissipation.
c
03. Finally, S is the thermal energy source term that accounts for curing of thermosets,
6
0 crystallization and melting of thermoplastics, and thermal decomposition. The equation
5-
99 of energy is coupled with the equation of motion through the viscous dissipation term
1
k- as well as the temperature-dependent viscosity. These two equations must be solved
b
1/ simultaneously along with the equation of continuity. This coupling can make the
2
10 modeling of polymer processing operations quite complex. But the most complicating
0.
1 factor is that Newton's law of viscosity does not adequately describe the relationship
oi: between stress and strain rate in polymers due to the highly viscoelastic nature of these
d
cs.org 1995 | materialFso. r Ma uflcuhi dm aotr ec ocnosmtapnlte xp rceosnsustrietu atinvde ewqiutha ticoonnss tamnut stt hbeer muasel dc o(n4d).u ctivity, and
s.a3, neglecting viscous dissipation, equation (3) reduces to
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August 19, 2Publication wsohliedr e Cp is the specific heat at copnsCtan|| t p=r esskuVrTe. For a fluid at rest as well as( 7fo)r a
p
This equation is typically used, along with the energy source term and appropriate
initial and boundary conditions, to model polymer heat transfer problems which do not
involve fluid flow, e.g. the curing of a thermoset, crystallinity development during
molding, and the response of a solid to a high heat flux. More detailed discussions
of the equations of change and their applications to polymers and polymer composites
may be obtained elsewhere (4-7),
Thermophysical Properties of Polymers and Polymer Composites
The specific heat, C, thermal conductivity, Κ and thermal diffusivity, a, are
p
thermophysical properties which must be known in order to adequately model the
In High-Temperature Properties and Applications of Polymeric Materials; Tant, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
4 HIGH-TEMPERATURE PROPERTIES AND APPLICATIONS OF POLYMERS
thermal behavior of polymers and composites during processing as well as during
application in thermal environments. For processing of thermosets, the heat of reaction
must be taken into account, and for thermoplastics, the energy of melting and
crystallization is important. For high-temperature applications, the kinetics of
decomposition and the thermochemical expansion (resulting from production of
pyrolysis gases) must be accounted for in any analysis. The thermal conductivity is
defined by Fourier's law for one-dimensional steady-state heat conduction, i.e. equation
(1). The thermal diffusivity is defined by
α = -JL (8)
PCZ>
where ρ is the density of the material.
1
0
0
ch Specific Heat The specific heat of amorphous polymers is usually in the range of
3.
0 0.7-2.5 kJ/kg-K, although specific heats as low as 0.2 and as high as 2.7 kJ/kg-K have
6
0
5- been observed for some polymers. The specific heat may decrease on crystallization,
9
9 while that for thermosetting polymers may be affected by the degree of cure.
1
k- Generally, the specific heat of polymer composites is a weighted average of the
b
21/ components.
0
1 Differential scanning calorimetry (DSC) is routinely used to measure the
0.
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s.org 995 | as the energetics of phase changes such as crystallization and melting. Because of the
c1 small sample size (-10 mg), the analyst must take care to ensure that the composition
bs.a13, of a polymer composite is representative of the material. While the application of
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2 | e: developed an iterative method to handle this problem, and this was later modified by
01Dat Henderson et al (10) to apply actual weight loss data.
9, 2on
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with crystalline solids where the lattice vibrations can be resolved into normal modes,
the quantization of which leads to the concept of phonons. The problem of calculating
thermal conductivity normally reduces to calculation of the number of phonons and
their mean free path (72). Unfortunately, this approach is not directly applicable to
polymers, since these materials are generally amorphous or only partially crystalline
because of their long-chain nature and tacticity which may be unfavorable for
crystallization.
The very low thermal conductivity of polymers is one of the primary reasons
for the very large effects of heat transfer on the structure and properties of these
materials. It is also the main reason that polymers and their composites are used in
insulating and thermal protection applications. Typically, the thermal conductivity of
amorphous polymers is in the range of 0.1-0.2 W/m-K (or J/s-m-K where J/s = W =
Watt). For oriented polymers, it has been experimentally determined that thermal
In High-Temperature Properties and Applications of Polymeric Materials; Tant, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.