Cirlex all-polyimide laminate Cirlex

Poly(4,4'-oxydiphenylene-pyromellitimide), the Kapton polyimide chemistry

Also known as Cirlex

Cirlex is a thick all-polyimide material made by Fralock from DuPont Kapton adhesiveless polyimide film, joined by Fralock's Adhesiveless Lamination Technology into one monolithic piece.

8 sources · Updated 2026-11-01 · CC BY 4.0

Evidence level

2 of 5

Lab-measured

High-temperature stiffness

402 kpsi at 200 degC

Electrical insulation

2790 V/mil

Heat flow

0.17 W/m K

Recipe, share of the weight

  • PMDA Molar mass 218.120 g/mol, Wikipedia infobox (CAS 89-32-7)Pyromellitic dianhydride
  • ODA Molar mass 200.24 g/mol, Wikipedia infobox (CAS 101-80-4); the Kapton article prints the name as oxydiphenylamine4,4'-Oxydianiline

Best for

Thick, dimensionally stable polyimide parts for thermal barriers, sealing shims, stand-offs and electrical isolation, where an adhesive-free laminate is wanted

Weakest at

Outgassing and long-term exposure to strong acids and strong oxidizers. The Fralock data sheet gives a total mass loss of 0.5 % in vacuum, and the Kapton safety sheet lists strong acids and strong oxidizers as incompatible.

Risk at a glance

  • People Low. No hazard classification on the family sheet
  • If it fails High. Use above the rated temperature
  • Corrosion Moderate. The Kapton safety sheet prints "Temperature > 400 °C" as a condition to avoid, while Cirlex is rated to 351 degC.

Quick facts: Cirlex

Key properties of Cirlex
PropertyValueBasis
Density1.421 sourced value
Yield strength42.1 MPa1 sourced value
Tensile strength224 MPa1 sourced value
Young's modulus2.28 GPa1 sourced value
Thermal conductivity0.17 W/(m·K)1 sourced value
Thermal expansion (CTE)30 to 118 ppm/K2 sourced values across conditions
Specific heat1,090 J/(kg·K)1 sourced value
Maximum service temperature351 °C1 sourced value

What is the density of Cirlex all-polyimide laminate?

Cirlex all-polyimide laminate has a density of 1.42. The source and test conditions are listed in the properties table on this page.

What is the thermal conductivity of Cirlex all-polyimide laminate?

Cirlex all-polyimide laminate has a thermal conductivity of 0.17 W/(m·K). The source and test conditions are listed in the properties table on this page.

What is the coefficient of thermal expansion of Cirlex all-polyimide laminate?

Cirlex all-polyimide laminate has a coefficient of thermal expansion of 30 to 118 ppm/K. The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.

What is the yield strength of Cirlex all-polyimide laminate?

Cirlex all-polyimide laminate has a yield strength of 42.1 MPa. The source and test conditions are listed in the properties table on this page.

What is the tensile strength of Cirlex all-polyimide laminate?

Cirlex all-polyimide laminate has a tensile strength of 224 MPa. The source and test conditions are listed in the properties table on this page.

What is Cirlex all-polyimide laminate used for?

Uses recorded in the sources include Thermal barriers and thermal shields; Flex and rigid-flex circuits, electrostatic chucks and flexible multizone heaters; Stand-offs, component stiffeners and washers with adhesive.

Why it exists

Cirlex is a thick all-polyimide laminate made by Fralock from DuPont Kapton film, without adhesive. Its Tg is 351 degC and its thermal conductivity is 0.17 W/m K, which is why Fralock sells it for thermal barriers and shims. Fralock's statement that it is used in aerospace is the only aerospace link in the sources read this run.

Where it's used

Thermal barriers and shields

The Fralock flyer lists thermal barriers and thermal shields as the first applications of Cirlex.

Electrical isolation and flexible electronics

The Fralock web page lists flex circuits, electrostatic chucks and flexible multizone heaters as customer uses, next to electrical insulators.

Recipe

Poly(4,4'-oxydiphenylene-pyromellitimide), the Kapton polyimide chemistry; Fralock prints no formula for Cirlex

Cirlex is made from DuPont Kapton adhesiveless polyimide film, using Fralock's Adhesiveless Lamination Technology to form a monolithic all-polyimide part. The Kapton chemistry is the condensation of pyromellitic dianhydride with an oxydianiline, followed by a thermal ring closure, per the Wikipedia Kapton article.

What Cirlex is made of
IngredientShare of the weightWhat it does
Pyromellitic dianhydride PMDA Molar mass 218.120 g/mol, Wikipedia infobox (CAS 89-32-7) Dianhydride monomer of the Kapton film, per Wikipedia Kapton article.
4,4'-Oxydianiline ODA Molar mass 200.24 g/mol, Wikipedia infobox (CAS 101-80-4); the Kapton article prints the name as oxydiphenylamine Diamine monomer of the Kapton film, per Wikipedia Kapton article.

Weight shares are as printed in the sources.

What it can do

High-temperature stiffness

402 kpsi at 200 degC

Fralock typical tensile modulus at 200 degC is 402 kpsi, with a glass transition temperature of 351 degC.

Electrical insulation

2790 V/mil

Fralock typical dielectric strength is 2790 V/mil, and the dielectric constant is 3.45 at 10 kHz.

Heat flow

0.17 W/m K

Fralock typical thermal conductivity is 0.17 W/m K, which the sheet presents as low.

How it compares

Cirlex is the thick, adhesive-free form of the Kapton chemistry. Fralock's typical data give a Tg of 351 degC, an in-plane CTE of 30 µm/m °C from 23 to 350 degC, and a through-thickness CTE of 118 µm/m °C, so the material expands much more through its thickness than in its plane. The Kapton film profiles in this database cover thin film, not thick laminate, so their outgassing and erosion numbers do not transfer to Cirlex without a test on the Cirlex grade.

The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details. Other materials are shown beside it; each was measured under its own conditions, so open its page before comparing closely. Compare every grade in the family.

Benchmarks
MeasurementCirlexPI (CP1)PI (Kapton H)PI (Kapton HN)PI (PMR-15)PI (Upilex-S)
Thermal behavior and safety
Thermal conductivity of Cirlex0.17 W/m K21no datano data0.12 W/(m K)no data0.29 W/(m.K)
Specific heat of Cirlex1.09 J/g K23no datano data1.09 J/(g K)no data1.13 kJ/(kg.K)
Water vapor regain (outgassing), ASTM E5950.42 %28no datano datano datano datano data
Temperature behavior
Glass transition temperature of Cirlex351 °C22263 °Cno datano data332 °Cno data
Other measurements
Ultimate compressive strength at 23 degC45.26 kpsi1no datano datano datano datano data
Ultimate compressive strength at 100 degC42.79 kpsi2no datano datano datano datano data
Ultimate compressive strength at 200 degC35.61 kpsi3no datano datano datano datano data
Ultimate tensile strength at 23 degC32.49 kpsi487 MPano datano datano data520 MPa
Ultimate tensile strength at 100 degC21.4 kpsi587 MPano datano datano data520 MPa
Ultimate tensile strength at 200 degC17.4 kpsi687 MPano datano datano data520 MPa
Ultimate tensile strength at 250 degC16.5 kpsi787 MPano datano datano data520 MPa
Tensile modulus at 23 degC330 kpsi82 GPano datano datano data9.1 GPa
Tensile modulus at 100 degC488 kpsi92 GPano datano datano data9.1 GPa
Tensile modulus at 200 degC402 kpsi102 GPano datano datano data9.1 GPa
Tensile modulus at 250 degC381 kpsi112 GPano datano datano data9.1 GPa
Tensile yield strength at 3 % elongation, 23 degC6.11 kpsi12no datano datano datano datano data
Tensile yield strength at 3 % elongation, 200 degC5.49 kpsi13no datano datano datano datano data
Shear strength at 100 degC6.4 kpsi14no datano datano datano datano data
Shear strength at 200 degC5.4 kpsi15no datano datano datano datano data
Poisson's ratio at 23 degC0.329 -16no datano datano datano datano data
Specific gravity of Cirlex1.42 -17no datano datano datano datano data
Dielectric strength of Cirlex2790 V/mil18no datano data303 kV/mmno data6.8 kV
Dielectric constant of Cirlex at 10 kHz3.45 -192.4 -no data3.4 (dimensionless)no data3.5 -
Dissipation factor of Cirlex0.004 -20no datano datano datano data0.0013 -
Coefficient of thermal expansion, in-plane30 µm/m °C2451 ppm/°Cno data20 ppm/Kno data12 ppm/°C
Coefficient of thermal expansion, through thickness118 µm/m °C2551 ppm/°Cno data20 ppm/Kno data12 ppm/°C
Total mass loss (outgassing TML)0.5 %26no datano datano datano datano data
Collected volatile condensable material (outgassing CVCM), upper bound< 0.01 %27no datano datano datano datano data
Lowest temperature the laminate keeps its integrity (Fralock claim)Features list, as printed in the Fralock flyer-269 °Cno data4 K-269 °Cno datano data
Highest temperature the laminate keeps its integrity (Fralock claim)Features list, as printed in the Fralock flyer351 °Cno data400 °C400 °C316 °Cno data

Why choose it, and why not

Good for

  • Thermal barriers and thermal shields where an adhesive-free all-polyimide part is wanted (Fralock flyer applications list).
  • Electrical isolation and standoffs, with a dielectric strength of 2790 V/mil and a dielectric constant of 3.45 at 10 kHz.
  • Parts that must keep their stiffness at high temperature, with a tensile modulus of 402 kpsi at 200 degC.

Watch out for

  • Outgassing in vacuum. The total mass loss is 0.5 % under ASTM E595, which the sheet reports without a bake-out procedure.
  • Strong acids and strong oxidizers, which the Kapton sheet lists as incompatible.
  • The Fralock values are typical averages and are not specification values. The 351 degC upper limit is a Fralock claim, not a rated limit for each part.
  • Atomic oxygen, radiation and thermal cycling for Cirlex were not found in any source read this run.

Cirlex is a thick, adhesive-free all-polyimide laminate from Fralock, with a glass transition temperature of 351 degC and a thermal conductivity of 0.17 W/m K. It suits thermal barriers, shims and electrical isolation where those numbers matter. For flight use, check outgassing (0.5 % total mass loss) and do not rely on typical values for specification.

Technical details

For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.

Other names and standards

The same grade under other systems, as datasheets and standards print them. Each code was checked against the page it comes from.

Other names and standards
SystemCodes
Trade nameCirlex

Notes

The method, full conditions and any caveat for the numbered rows above.

Notes for the numbered rows
#MeasurementMethodConditionsCaveat
1Ultimate compressive strength at 23 degCTypical value printed in the Fralock data sheet table (Mechanical Property), averagedtemperature 23 °C (73.4 degF)standard ASTM D695-15basis typical value, Cirlex all-polyimide laminate—
2Ultimate compressive strength at 100 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 100 °C (212 degF)standard ASTM D695-15basis typical value, Cirlex all-polyimide laminate—
3Ultimate compressive strength at 200 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 200 °C (392 degF)standard ASTM D695-15basis typical value, Cirlex all-polyimide laminate—
4Ultimate tensile strength at 23 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 23 °C (73.4 degF)standard ASTM D638basis typical value, Cirlex all-polyimide laminate—
5Ultimate tensile strength at 100 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 100 °C (212 degF)standard ASTM D638basis typical value, Cirlex all-polyimide laminate—
6Ultimate tensile strength at 200 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 200 °C (392 degF)standard ASTM D638basis typical value, Cirlex all-polyimide laminate—
7Ultimate tensile strength at 250 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 250 °C (482 degF)standard ASTM D638basis typical value, Cirlex all-polyimide laminate—
8Tensile modulus at 23 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 23 °C (73.4 degF)standard ASTM D638basis typical value, Cirlex all-polyimide laminate—
9Tensile modulus at 100 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 100 °C (212 degF)standard ASTM D638basis typical value, Cirlex all-polyimide laminate—
10Tensile modulus at 200 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 200 °C (392 degF)standard ASTM D638basis typical value, Cirlex all-polyimide laminate—
11Tensile modulus at 250 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 250 °C (482 degF)standard ASTM D638basis typical value, Cirlex all-polyimide laminate—
12Tensile yield strength at 3 % elongation, 23 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 23 °C (73.4 degF)standard ASTM D638basis typical value; the sheet prints the yield as the stress at 3 % elongation—
13Tensile yield strength at 3 % elongation, 200 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 200 °C (392 degF)standard ASTM D638basis typical value; the sheet prints the yield as the stress at 3 % elongation—
14Shear strength at 100 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 100 °C (212 degF)standard ASTM D3846basis typical value, Cirlex all-polyimide laminate—
15Shear strength at 200 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 200 °C (392 degF)standard ASTM D3846basis typical value, Cirlex all-polyimide laminate—
16Poisson's ratio at 23 degCTypical value printed in the Fralock data sheet table (Mechanical Property)temperature 23 °C (73.4 degF)standard ASTM D3039-17basis typical value, Cirlex all-polyimide laminate—
17Specific gravity of CirlexPhysical Property table, row Specific Gravity, as printed in the Fralock data sheetbasis typical value; the sheet gives no temperature for this row—
18Dielectric strength of CirlexElectrical Property table, row Dielectric Strength, as printed in the Fralock data sheetbasis typical value; the flyer prints the same figure as a lower bound (greater than 2790 volts/mil)—
19Dielectric constant of Cirlex at 10 kHzElectrical Property table, row Dielectric Constant DC at 10 kHzfrequency 10 kHztemperature 25 °Cstandard ASTM D150basis typical value—
20Dissipation factor of CirlexElectrical Property table, row Dielectric Constant Dissipation Factorstandard ASTM D150basis typical value; the table prints no test frequency for this row—
21Thermal conductivity of CirlexThermal Property table, row Thermal Conductivity, as printed in the Fralock data sheettemperature not printed in the tablebasis typical value, Cirlex all-polyimide laminate—
22Glass transition temperature of CirlexThermal Property table, row Glass Transition, Tg, as printed in the Fralock data sheetbasis typical value, Cirlex all-polyimide laminate—
23Specific heat of CirlexThermal Property table, row Specific Heat, as printed in the Fralock data sheettemperature not printed in the tablebasis typical value, Cirlex all-polyimide laminate—
24Coefficient of thermal expansion, in-planeThermal Property table, row CTE In-plane, as printed in the Fralock data sheettemperature range 23 to 350 °Cstandard ASTM E831basis typical value, Cirlex all-polyimide laminate—
25Coefficient of thermal expansion, through thicknessThermal Property table, row CTE Thru-thickness, as printed in the Fralock data sheettemperature range 23 to 350 °Cstandard ASTM E831basis typical value, Cirlex all-polyimide laminate—
26Total mass loss (outgassing TML)Thermal Property table, row Outgassing TML, as printed in the Fralock data sheetstandard ASTM E595basis typical value; the table prints 0.5% (the flyer prints 0.50%)—
27Collected volatile condensable material (outgassing CVCM), upper boundThermal Property table, row Outgassing CVCM, as printed in the Fralock data sheetstandard ASTM E595basis printed as less than 0.01 %, so 0.01 is an upper bound—
28Water vapor regain (outgassing), ASTM E595Thermal Property table, row Outgassing Water Vapor Regain, as printed in the Fralock data sheetstandard ASTM E595basis typical value—

Corrosion and compatibility

What happens when it meets other materials and environments.

Corrosion and compatibility
EnvironmentConcernWhat happens
Strong acids and strong oxidizers not rated The Kapton safety sheet lists strong acids and strong oxidizers as incompatible with the film, and gives no rate.1
Humid air (water uptake) low Cirlex regains 0.42 % water vapor on the outgassing test, a small uptake.2
Heat above the family limit moderate The Kapton safety sheet prints "Temperature > 400 °C" as a condition to avoid, while Cirlex is rated to 351 degC.3
Corrosion details
#EnvironmentDetailsTest conditions
1 Strong acids and strong oxidizers The sheet names strong acids and strong oxidizers as incompatible and gives no test or rate. Fralock describes the laminate as chemically inert but gives no test for it. basis Kapton FPC, HN and related family sheet, version 2.2 (the H grade is not named on the sheet)
2 Humid air (water uptake) The Fralock sheet prints a water vapor regain of 0.42 % under ASTM E595. The sheet does not give a humidity-exposure test, so the rating below is our reading of that single value. standard ASTM E595, water vapor regain
3 Heat above the family limit Two sources give different limits for the film family and for this laminate. The Kapton sheet prints "Temperature > 400 °C" as a condition to avoid. The Fralock flyer gives 351 degC as the upper limit of integrity for Cirlex. The laminate limit is the lower of the two. basis the sources are printed side by side, not reconciled

Risks and side effects

Hazards to people, what happens when a cell overheats, and how the material is handled and stored.

For people

The DuPont family sheet gives no hazard classification for the film. Thick laminate can cut, and unwrapping can build up static.

The laminate
The Kapton family sheet lists no hazard classification and says inhalation and ingestion are not considered routes of exposure. Thick films have sharp edges that can cut.
Fire
The sheet says the film does not burn in air but will burn in 100% oxygen.
Static
Processing and unwrapping can generate static charge, so the sheet advises avoiding static discharge.

If it fails

The failure modes come from the datasheet limits and the incompatibility list, not from tests on finished hardware.

Temperature
The Kapton sheet prints "Temperature > 400 °C" as a condition to avoid, and Cirlex is rated to 351 degC in the Fralock flyer.
Chemicals
Strong acids and strong oxidizers are listed as incompatible, with no rate of attack given.
Vacuum
The laminate loses 0.5 % of its mass in the ASTM E595 test, so it can add volatiles in a sealed vacuum volume.

Handling and storage

Storage
Keep the film dry, away from strong acids and strong oxidizers. The Kapton sheet gives the storage temperature as "20 - 30 °C".
Static
Avoid static discharge when unwrapping, and avoid breathing dust.

Test details
The original wording and numbers from the sources, for readers who want them.

Failure risks

Failure risks
FailureTrigger and consequence
Attack by strong acids and strong oxidizersmoderate severityContact with strong acids or strong oxidizersThe film is listed as incompatible with them. No rate of attack is given for the laminate.
Use above the rated temperaturehigh severityExposure above the Kapton sheet's "Temperature > 400 °C" condition to avoidCirlex is rated to 351 degC in the Fralock flyer, so use above that rating is outside the stated range.
Mass loss and condensed volatiles in vacuumlow severityUse in vacuum, such as a spacecraft interior or a sealed instrumentTotal mass loss of 0.5 % and CVCM below 0.01 % under ASTM E595. Condensable volatiles may deposit on nearby optics.

Side effects on surrounding parts

Side effects on surrounding parts
AffectsEffect
SurroundingsThe Fralock data sheet prints an outgassing water vapor regain of 0.42 % under ASTM E595. The sheet does not say that moisture affects the laminate in use.

Handling and storage

  • The Kapton sheet gives the storage temperature as "20 - 30 °C" and says "Keep in a dry place" for the family. The sheet does not name Cirlex separately.
  • Take action to avoid static discharge when unwrapping and processing. Avoid breathing dust. Thick films have sharp edges which can cause cuts.

Supply and geography

How common the raw materials are and where they come from.

Cirlex all-polyimide laminate

Not read in a fetched page for this product.

Top producers
USA (2023), USA, USA (2025)
Recycling
Not sourced.
Substitutes
Fralock names ceramic and Vespel as materials that Cirlex can replace (Fralock generic data sheet, first page).

Updated