ASTM D1673-94(1998)

Standard Test Methods for Relative Permittivity And Dissipation Factor of Expanded Cellular Polymers Used For Electrical Insulation

SCOPE
1.1 These test methods cover procedures for determining the relative permittivities and dissipation factor of flat sheets or slabs of expanded cellular polymers of both the rigid and flexible types, at frequencies from 60 Hz to 100 MHz. Provision is made for measurements on specimens up to 50 mm (2 in.) in thickness, but it is recommended that specimens greater than 25 mm (1 in.) in thickness shall be tested at frequencies up to a maximum of only about 1 MHz.  
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use .

General Information

• Status: Historical
• Publication Date: 09-Oct-1998
• ICS: 29.035.20 - Plastics and rubber insulating materials
• Technical Committee: D09 - Electrical and Electronic Insulating Materials
• Drafting Committee: D09.12 - Electrical Tests

Relations

• Replaced By: ASTM D1673-94(2004) - Standard Test Methods for Relative Permittivity And Dissipation Factor of Expanded Cellular Polymers Used For Electrical Insulation (Withdrawn 2006)
• Effective Date: 01-Mar-2004

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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An American National Standard
Designation: D 1673 – 94 (Reapproved 1998)
Standard Test Methods for
Relative Permittivity And Dissipation Factor of Expanded
Cellular Polymers Used For Electrical Insulation
This standard is issued under the fixed designation D 1673; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Although fundamentally similar to test methods used for solid electrical insulating materials in sheet
or plate form, certain modifications in the procedures and measurement techniques are necessary for
the proper determination of the relative permittivities and dissipation factors of foamed or expanded
cellular polymers. This is occasioned by the fact that in many, if not most, instances expanded cellular
materials have surfaces that preclude the use of conventional electrodes such as metal foil attached by
petrolatum and similar adhesives, or conducting silver paint applied by brushing or spraying.
Furthermore, it is generally true that slabs or plates of expanded cellular materials are available only
in substantially greater thicknesses than those commonly used for test specimens of solid insulation.
1. Scope Sponge or Expanded Rubber
D 1711 Terminology Relating to Electrical Insulating Ma-
1.1 These test methods cover procedures for determining
terials
the relative permittivities and dissipation factor of flat sheets or
slabs of expanded cellular polymers of both the rigid and
3. Terminology
flexible types, at frequencies from 60 Hz to 100 MHz.
3.1 For definitions of relative permittivity, dissipation fac-
Provision is made for measurements on specimens up to 50
tor, and loss index, refer to Test Methods D 150 or Terminol-
mm (2 in.) in thickness, but it is recommended that specimens
ogy D 1711.
greater than 25 mm (1 in.) in thickness shall be tested at
frequencies up to a maximum of only about 1 MHz.
4. Significance and Use
1.2 This standard does not purport to address all of the
4.1 Relative Permittivity:
safety concerns, if any, associated with its use. It is the
4.1.1 Because a relatively large proportion of their volumes
responsibility of the user of this standard to establish appro-
are composed of more or less uniformly distributed, isolated or
priate safety and health practices and determine the applica-
interconnected gas-filled cells, foamed or expanded cellular
bility of regulatory limitations prior to use.
polymers always have lower relative permittivities, at a given
2. Referenced Documents frequency and temperature, than the solid base resins from
which they are prepared.
2.1 ASTM Standards:
4.1.2 The relative permittivities of expanded cellular poly-
D 150 Test Methods for AC Loss Characteristics and Per-
mers are important because they determine the increase in
mittivity (Dielectric Constant) of Solid Electrical Insulat-
2 capacitance between conductors, or between conductors and
ing Materials
ground, that will result when a circuit or component is
D 374 Test Methods for Thickness of Solid Electrical Insu-
2 encapsulated in such a material, over their corresponding
lation
values before encapsulation (when air is the surrounding
D 1056 Specification for Flexible Cellular Materials
medium). Likewise, the relative permittivities of an expanded
cellular polymer may serve as a measure of the decrease of
such capacitances caused by substitution of the expanded
These test methods are under the jurisdiction of ASTM Committee D-9 on material for a solid encapsulating compound or resin of known
Electrical and Electronic Insulating Materials and are the direct responsibility of
relative permittivity.
Subcommittee D 09.12 on Electrical Tests.
Current edition approved Jan. 15, 1994. Published March 1994. Originally
e1
published as D 1673 – 59 T. Last previous edition D 1673 – 79 (1989) .
2 3
Annual Book of ASTM Standards, Vol 10.01. Annual Book of ASTM Standards, Vol 09.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 1673 – 94 (1998)
4.1.3 In transmission lines, such as coaxial cable, television 5. Apparatus
lead-in cables, etc., the reduction of relative permittivity of an
5.1 Electrical Measurement Apparatus, consisting of suit-
expanded material from its value in the original solid state has
able bridge and resonant-circuit equipment having character-
significant usefulness in design, since the capacitance per foot
istics as prescribed in Test Methods D 150. Provision shall be
of cable, and such cable characteristics as velocity of propa-
made for the performance of relative permittivity and dissipa-
gation and characteristic impedance are all dependent upon the
tion factor tests at any desired frequency in the range between
relative permittivity of the insulating material.
60 Hz and 100 MHz.
4.1.4 In wave guides, radomes, dielectric lenses, etc., for
6. Electrodes
use at radio frequencies, if the cellular polymer is nonmagnetic,
the relative permittivity (usually in combination with the
6.1 Expanded cellular polymers, in general, do not have
dissipation factor) determines such transmission characteristics
surfaces suitable for attachment of conventional metal foil or
as velocity of propagation, attenuation distance, decibel loss
conducting paint electrodes, so that prefabricated rigid metal
per meter, phase factor, complex index of refraction, index of plate electrodes must usually be employed for relative permit-
absorption, and dielectric conductivity.
tivity and dissipation factor tests. Such electrode systems may
be of either the direct contact type or the noncontacting type.
4.1.5 The relative permittivity determination may serve as a
6.2 Direct-Contact Electrode Systems— Direct-contact type
production control test for batch-to-batch uniformity of a given
electrodes may be one of the following:
expanded cellular polymer. For expanded cellular nonpolar
6.2.1 A calibrated micrometer electrode system of the
polymers (polyethylene, polystyrene, etc.), the relative permit-
Hartshorn-Ward type, shown in Fig. 1 (Fig. 10 of Test Methods
tivity measurement may constitute a useful control test on the
D 150), is particularly useful for samples 50 mm (2 in.) in
density of the product.
diameter and up to about 6.35 mm (0.25 in.) thick. This system
NOTE 1—For useful information concerning the relationship of the
may be used at any frequency up to 100 MHz. Specimens are
relative permittivity of an expanded cellular material to its density and to
lightly clamped and in contact with both electrodes. Care must
the relative permittivity of the solid constituent, see Appendix X1.
be observed to avoid compressing or crushing the material.
4.2 Dissipation Factor and Loss Index: 6.2.2 Two rigid plate electrodes with a single sheet speci-
men between and in contact with them may be used with the
4.2.1 The loss index of an expanded cellular polymer is a
specimen the same size as the electrodes (see Table 1). It may
measure of the ac power loss in the material. When two
be desirable to enclose this system in a metal box for shielding.
materials have the same relative permittivities, their relative
A wide range of specimen sizes and thicknesses may be
dielectric losses per unit volume at a given frequency and
handled by various modifications of this system. However, the
applied voltage gradient are directly indicated by their respec-
upper frequency limit is relatively low for larger thick speci-
tive dissipation factors.
mens.
4.2.2 Since the dielectric loss in an insulating material
6.2.3 A three-plate electrode system with a double specimen
results in the generation of heat, with a subsequent rise in
arranged in a sandwich form may be used and is recommended
temperature of the material, it is desirable in most cases that
for large sheets of thick materials for tests at relatively low
these losses be as low as possible. This is important not only
frequencies. The two specimens should be of nearly the same
from the standpoint of the overall efficiency of an electrical
thickness. The two outer plates are connected together and to
system but also because the increased temperature generally
ground or to the low side of the measuring apparatus. The third
causes significant changes in both the relative permittivity and
(middle) electrode serves as the high side. The system has the
loss and thereby may contribute to instability of operation,
advantage of being practically self-shielding.
particularly in radio-frequency circuits.
6.3 Noncontacting Electrode Systems (“Air Gap” Methods):
4.2.3 The dielectric loss, as measured by the dissipation
6.3.1 A calibrated micrometer electrode system of the
factor and loss index, may serve as a quality control criterion
Hartshorn-Ward type, shown in Fig. 1 may be used, with the
and as a means of determining batch-to-batch uniformity of a
product. It is also an excellent means of measuring the effects
of weathering, aging, and absorption of moisture by the
expanded cellular polymer, these influences generally resulting
in substantial increases in the dielectric loss index.
4.2.4 The dissipation factor (usually in combination with
the relative permittivity) is useful in estimating the contribution
of the dielectric loss to the total attenuation in coaxial cables,
and in calculations of the transmission characteristics of
radomes, dielectric lenses, and related devices, as indicated in
4.1.4.
For details see von Hippel, A. R., Dielectrics and Waves, Part I, John Wiley &
Sons, Inc., New York, NY 1954, Ch. 9, pp. 26–37. FIG. 1 Micrometer Electrode System
D 1673 – 94 (1998)
TABLE 1 Suggested Specimen and Electrode Sizes and Maximum Test Frequencies for Relative Permittivity and Dissipation Factor
Measurements on Expanded Cellular Plastic Sheets of Various Thicknesses up to 50 mm (2 in.).
Thickness of Specimen Approximate Diameter of Round, or Length of Side of Square Specimens and Electrodes Test Frequency, max, Approximate MHz
Recommended Permissible
mm in. Recommended Permissible
mm in. mm in.
A
Up to 6.35 0.25 101.6 4.0 50.8 2.0 10.0 50: 100
12.7 0.50 152.4 6.0 50.8 2.0 1.0 50
19.05 0.75 203.2 8.0 101.6 4.0 1.0 10
25.4 1.0 203.2 8.0 101.6 4.0 1.0 10
38.1 1.5 304.8 12.0 152.4 6.0 0.1 1
50.8 2.0 304.8 to 406.4 12 to 16 203.2 8.0 0.1 1
A
A frequency of 100 MHz is permissible only with micrometer electrode system (Fig. 1).
specimen t
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