ASTM C1594-23

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C1594 − 11 (Reapproved 2017) C1594 − 23
Standard Specification for
Polyimide Rigid Cellular Thermal Insulation
This standard is issued under the fixed designation C1594; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This specification covers the composition and physical properties of polyimide foam insulation with nominal densities from
3 3 3 3
1.0 lb/ft to 8.0 lb/ft (16 kg ⁄m to 128 kg/m ) and intended for use as thermal and sound-isolating insulation for temperatures from
−423°F to +600°F (−253°C to +316°C) in commercial and industrial environments.
1.1.1 The annex shall apply to this specification for marine applications.
1.1.2 This standard is designed as a material specification and not a design document.
1.1.3 The values stated in Table 1 and Table 2 are not to be used as design values. It is the buyer’s responsibility to specify design
requirements and obtain supporting documentation from the material supplier.
NOTE 1—The subject matter of this material specification is not covered by any other ASTM specification. There is no known ISO standard covering the
subject of this standard.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.3 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 healthsafety, health, and environmental practices and determine
the applicability of regulatory requirementslimitations prior to use.
NOTE 1—The subject matter of this material specification is not covered by any other ASTM specification. There is no known ISO standard covering the
subject of this standard.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C168 Terminology Relating to Thermal Insulation
This specification is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.22 on Organic and
Nonhomogeneous Inorganic Thermal Insulations.
Current edition approved March 1, 2017March 1, 2023. Published March 2017April 2023. Originally approved in 2004. Last previous edition approved in 20112017 as
C1594 – 11.C1594 – 11 (2017). DOI: 10.1520/C1594-11R17.10.1520/C1594-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1594 − 23
TABLE 1 Polyimide Foam Classification (inch pound)
Type II Type II Type II Type II Type II Type II
Type I Type I Type I Type III
Property Grade 1 Grade 2 Grade 3 Grade 1 Grade 2 Grade 3
Grade 1 Grade 2 Grade 3 Grade 4
Class 1 Class 1 Class 1 Class 2 Class 2 Class 2
Density, lb/ft (max) 8.0 6.0 3.0 8.0 6.0 3.0 8.0 6.0 3.0 1.5
Thermal Conductivity,
Btu-in./h-ft -°F (max)
-238°F * * * * * 0.048 * * * *
-150°F * * * * * 0.036 * * * *
-50°F * * * * * 0.096 * * * *
24°F 0.230 0.220 0.210 * * 0.180 * * * *
65°F 0.248 0.238 0.220 * * 0.228 * * * *
75°F 0.250 0.240 0.240 0.260 0.250 0.246 0.234 0.250 0.225 0.240
100°F 0.260 0.250 0.250 * * 0.264 * * * *
150°F 0.280 0.270 0.270 * * 0.324 * * * *
200°F 0.305 0.295 0.300 * * 0.396 * * * *
300°F * * * * * 0.516 * * * *
572°F * * * * * 0.876 NA NA NA *
Upper Temperature Limit – test temperature for 600 600 600 600 600 600 400 400 400 600
C411, °F
High Temperature Stability – % of initial tensile * * * * * 95 * * * *
strength retained
after 1000 hours in air oven at 572°F, (min.)
Tensile Strength PSI (min.) 244 134 41 180 80 14 180 80 14 41
Compressive Strength PSI @ 10% def. (min.) 95 65 28 * * * * * * *
Compressive Force Deflection PSI @ 20% def. * * * 18 6 2 18 6 2 26
(min.)
Steam Aging 25 25 25 25 25 25 25 25 25 25
Change in tensile Strength % (max.) 10 10 10 10 10 10 10 10 10 10
Dimensional and weight changes % (max.)
Water Vapor Permeability Perm in. (max.) 0.5 0.5 3.5 2.5 5.0 8.0 2.0 2.5 5.0 2.9
Oxygen Index % (min.) 46 45 43 52 50 48 30 30 30 47
Surface Burning Characteristics, 2 in. thickness 10 10 10 10 10 10 10 10 10 10
Flame Spread Index, (max.) 15 15 15 15 15 15 15 15 15 15
Smoke Developed Index, (max.)
Vertical Burn
Flame Application sec 60 60 60 60 60 60 60 60 60 60
Flame Time sec (max.) 0 0 0 0 0 0 0 0 0 0
Burn Length in. (max.) 0.6 0.6 1.6 0.5 0.6 0.6 0.6 0.6 0.8 0.6
Dripping None None None None None None None None None None
Specific Optical Density 3 2 1 2 2 2 5 5 5 1
Avg. Dm. Flaming Exposure (max.) 3 2 1 1 1 1 3 3 3 1
Avg. Dm. Non-Flaming Exposure (max.)
Corrosiveness Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
Chemical resistance Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
By-Products of Combustion, ppm (max.)
Carbon Monoxide 275 200 100 300 300 300 300 300 300 125
Flaming 3 2 1 10 10 10 10 10 10 3
Non-Flaming
Hydrogen Fluoride 5 4 4 5 5 5 5 5 5 2
Flaming 5 4 4 5 5 5 5 5 5 2
Non-Flaming
Hydrogen Chloride 9 7 5 10 10 10 10 10 10 3
Flaming 9 7 5 10 10 10 10 10 10 3
Non-Flaming
Nitrogen Oxides 10 10 10 10 10 10 10 10 10 6
Flaming 10 10 10 10 10 10 10 10 10 3
Non-Flaming
Sulfur Dioxide 5 5 5 5 5 5 5 5 5 2
Flaming 5 5 5 5 5 5 5 5 5 2
Non Flaming
Hydrogen Cyanide 5 5 5 5 5 5 10 10 10 4
Flaming 5 5 5 5 5 5 5 5 5 3
Non Flaming
⁄4 Scale Room Burn – No Flash Over Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
Percent closed cell (range) 100–76 100–76 100–76 30–0 30–0 30–0 30–0 30–0 30–0 75–20
Tumbling Friability
600 Revolutions, mass loss, max, % 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0
1200 Revolutions, mass loss, max, % 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0
Odor Emission Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
Fungi Resistance Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
Wicking, 48 hrs, distance above water line, 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
max. @ 72°F, in.
* = Not available consult manufacturer for additional information.
NA = Not Applicable
NB = A manufacturer can only claim conformance to this standard to the values reported in this table. The * notes are confidential data to the manufacturers and as such
C1594 − 23
are not considered part of any qualifying requirements for the standard and only tell the user to inquire about that data.
C177 Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the
Guarded-Hot-Plate Apparatus
C335 Test Method for Steady-State Heat Transfer Properties of Pipe Insulation
C390 Practice for Sampling and Acceptance of Thermal Insulation Lots
C411 Test Method for Hot-Surface Performance of High-Temperature Thermal Insulation
C421 Test Method for Tumbling Friability of Preformed Block-Type and Preformed Pipe-Covering-Type Thermal Insulation
C447 Practice for Estimating the Maximum Use Temperature of Thermal Insulations
C518 Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus
C634 Terminology Relating to Building and Environmental Acoustics
C665 Specification for Mineral-Fiber Blanket Thermal Insulation for Light Frame Construction and Manufactured Housing
C1045 Practice for Calculating Thermal Transmission Properties Under Steady-State Conditions
C1058 Practice for Selecting Temperatures for Evaluating and Reporting Thermal Properties of Thermal Insulation
C1114 Test Method for Steady-State Thermal Transmission Properties by Means of the Thin-Heater Apparatus
C1304 Test Method for Assessing the Odor Emission of Thermal Insulation Materials
C1338 Test Method for Determining Fungi Resistance of Insulation Materials and Facings
C1482 Specification for Polyimide Flexible Cellular Thermal and Sound Absorbing Insulation
C1559 Test Method for Determining Wicking of Fibrous Glass Blanket Insulation (Aircraft Type)
D543 Practices for Evaluating the Resistance of Plastics to Chemical Reagents
D638 Test Method for Tensile Properties of Plastics
D1621 Test Method for Compressive Properties of Rigid Cellular Plastics
D2126 Test Method for Response of Rigid Cellular Plastics to Thermal and Humid Aging
D2863 Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics
(Oxygen Index)
D3574 Test Methods for Flexible Cellular Materials—Slab, Bonded, and Molded Urethane Foams
D6226 Test Method for Open Cell Content of Rigid Cellular Plastics
E84 Test Method for Surface Burning Characteristics of Building Materials
E96/E96M Test Methods for Gravimetric Determination of Water Vapor Transmission Rate of Materials
E176 Terminology of Fire Standards
E662 Test Method for Specific Optical Density of Smoke Generated by Solid Materials
E2231 Practice for Specimen Preparation and Mounting of Pipe and Duct Insulation Materials to Assess Surface Burning
Characteristics
2.2 U.S. Federal Standards:
FAR 25.853(a), Appendix F, Part 1, (a) (1) (i) Test Criteria and Procedures for Showing Compliance with Sec. 25.853, or 25.855
2.3 Private Sector Standards:
Boeing BSS 7239 Test Method for Toxic Gas Generation by Materials on Combustion
3. Terminology
3.1 Definitions—Terms used in this specification are defined in Terminology C168, Terminology C634, and Terminology E176.
In the case of a conflict, Terminology C168 shall be the dominant authority.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 slab—a rectangular section, piece, or sheet of foam that is cut from a bun, or block of foam.
4. Classification
4.1 The polyimide cellular insulations of the specification are classified into Types I, II and III. Type I is polyimide foam with a
closed cell content of greater than 75 % and Type II is open celled polyimide foam with a closed cell content of less than 30 %.
Type III is polyimide foam with a closed cell content of between 20 and 75 %. The polyimide cellular insulation is further classified
into grades according to density.
3 3
4.1.1 Grade 1—Densities to 8.0 lb/ft (128 kg/m ).
Federal Aviation Regulations Part 25 (Airworthiness Standards, Transport Category Aircraft, and Section 25.853. Procedure in appendix F, Part I (a) (1) (i) and (ii).
Available from Superintendent of Documents, U.S. Government Printing Office P.O. Box 371954, Pittsburgh, PA 15250-7954.
Available from Boeing Commercial Airplane Group, Material Division, P.O. Box 3707, Seattle, WA 98124-2207.
C1594 − 23
TABLE 2 Polyimide Foam Classification (SI)
Type II Type II Type II Type II Type II Type II
Type I Type I Type I Type III
Property Grade 1 Grade 2 Grade 3 Grade 1 Grade 2 Grade 3
Grade 1 Grade 2 Grade 3 Grade 4
Class 1 Class 1 Class 1 Class 2 Class 2 Class 2
Density, kg/m (max) 128 96 48 128 96 48 128 96 48
Thermal Conductivity,
W/m-K (max)
-150°C * * * * * 0.007 * * * *
-101°C * * * * * 0.005 * * * *
-46°C * * * * * 0.014 * * * *
-4°C 0.033 0.032 0.030 * * 0.026 * * * *
18°C 0.036 0.034 0.032 * * 0.033 * * * *
24°C 0.036 0.035 0.035 0.038 0.036 0.036 0.034 0.036 0.032 0.035
38°C 0.038 0.036 0.036 * * 0.038 * * * *
66°C 0.040 0.039 0.039 * * 0.047 * * * *
93°C 0.044 0.042 0.043 * * 0.057 * * * *
149°C * * * * * 0.074 * * * *
300°C * * * * * 0.126 NA NA NA *
Upper Temperature Limit – test temperature for 315 315 315 315 315 315 204 204 204 315
C411 °C
High Temperature Stability – % of initial tensile * * * * * 95 * * * *
strength retained
after 1000 hours in air oven at 300°C, (min.)
Tensile Strength MPa (min.) 1.68 0.92 0.28 1.24 0.55 0.096 1.24 0.55 0.096 0.28
Compressive Strength MPa @ 10% def. (min.) 0.65 0.45 0.19 * * * * * * *
Compressive Force Deflection MPa @ 20% * * * 0.12 0.04 0.01 0.12 0.04 0.01 0.18
def. (min.)
Steam Aging 25 25 25 25 25 25 25 25 25 25
Change in tensile Strength % (max) 10 10 10 10 10 10 10 10 10 10
Dimensional and weight changes % (max)
-9 -9 -9 -9 -9 -9 -9 -9 -9 -9
Water Vapor Permeability g/Pa s m (max.) 0.7×10 0.7×10 5.1×10 3.6×10 7.3×10 11.6×10 2.9×10 3.6×10 7.3×10 4.2×10
Oxygen Index % (min.) 46 45 43 52 50 48 30 30 30 47
Surface Burning Characteristics, 50mm thick- 10 10 10 10 10 10 10 10 10 10
ness 15 15 15 15 15 15 15 15 15 15
Flame Spread Index, (max.)
Smoke Developed Index, (max.)
Vertical Burn
Flame Application sec 60 60 60 60 60 60 60 60 60 60
Flame Time sec (max.) 0 0 0 0 0 0 0 0 0 0
Burn Length cm (max.) 1.5 1.5 4.0 1.3 1.4 1.4 1.4 1.4 2.0 1.4
Dripping None None None None None None None None None None
Specific Optical Density 3 2 1 2 2 2 5 5 5 1
Avg. Dm. Flaming Exposure (max) 3 2 1 1 1 1 3 3 3 1
Avg. Dm. Non-Flaming Exposure (max.)
Corrosiveness Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
Chemical resistance Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
By-Products of Combustion, ppm (max.)
Carbon Monoxide 275 200 100 300 300 300 300 300 300 125
Flaming 3 2 1 10 10 10 10 10 10 3
Non-Flaming
Hydrogen Fluoride 5 4 3 5 5 5 5 5 5 2
Flaming 5 4 3 5 5 5 5 5 5 2
Non-Flaming
Hydrogen Chloride 9 7 5 10 10 10 10 10 10 3
Flaming 9 7 5 10 10 10 10 10 10 3
Non-Flaming
Nitrogen Oxides 10 10 10 10 10 10 10 10 10 6
Flaming 10 10 10 10 10 10 10 10 10 3
Non-Flaming
Sulfur Dioxide 5 5 5 5 5 5 5 5 5 2
Flaming 5 5 5 5 5 5 5 5 5 2
Non-Flaming
Hydrogen Cyanide 5 5 5 5 5 5 10 10 10 4
Flaming 5 5 5 5 5 5 5 5 5 3
Non-Flaming
⁄4 Scale Room Burn – No Flash Over Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
Percent closed cell (range) 100–76 100–76 100–76 30–0 30–0 30–0 30–0 30–0 30–0 75–20
Tumbling Friability
600 Revolutions, mass loss, max, % 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0
1200 Revolutions, mass loss, max, % 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0
Odor Emission Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
Fungi Resistance Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
Wicking, 48 hrs, distance above water line, 13.0 13.0 13.0 13.0 13.0 13.0 13.0 13.0 13.0 13.0
max. @ 22°C, mm
* = Not available consult manufacturer for additional information.
NA = Not Applicable
C1594 − 23
NB = A manufacturer can only claim conformance to this standard to the values reported in this table. The * notes are confidential data to the manufacturers and as such
are not considered part of any qualifying requirements for the standard and only tell the user to inquire about that data.
3 3
4.1.2 Grade 2—Densities to 6.0 lb/ft (96 kg/m ).
3 3
4.1.3 Grade 3—Densities to 3.0 lb/ft (48 kg/m )
3 3
4.1.4 Grade 4—Densities to 1.5 lb/ft (24 kg/m )
4.2 Type II polyimide cellular insulation is further divided into Classes 1 and 2 based on Upper Temperature Limits of 600°F and
400°F (316°C and 204°C) respectively.
4.3 Use Upper Temperature Limi
...