Kapton® FWR Hydrolysis Resistant Heat-Fusible Polyimide-FEP Composite Film
Kapton® FWR is a heat-fusible polyimide-FEP fluoropolymer composite film providing tough, high dielectric strength insulation with significantly improved hydrolysis resistance compared to other commonly used polyimide materials, including higher modulus and lower water vapor permeability than equivalent Kapton® FN films. Tensile strength is 34 kpsi (234 MPa) for 150FWR019 and 30 kpsi (207 MPa) for 200FWR919. The film carries UL Electrical RTI 240°C, UL Mechanical RTI 200°C, and UL 94 V-0 ratings. Available in two constructions.
Key Properties
- Tensile Strength: 150FWR019: 34 kpsi (234 MPa); 200FWR919: 30 kpsi (207 MPa) — ASTM D882
- Elongation: 150FWR019: 60%; 200FWR919: 63% — ASTM D882
- Dielectric Strength: 150FWR019: 4500 V/mil (177 kV/mm); 200FWR919: 5000 V/mil (197 kV/mm) — ASTM D149
- UL Electrical RTI / Mechanical RTI: 240°C / 200°C — UL746B
- Thickness: 150FWR019: 1.5 mil (38 µm); 200FWR919: 2.0 mil (50 µm) — ASTM D374
- Density: 150FWR019: 1.69 g/cc; 200FWR919: 1.83 g/cc — ASTM D1505
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- Specifications
- Applications
- General Info
- FAQs
Physical Properties
| Property | 150FWR019 | 200FWR919 | Test Method |
| Thickness, mil (µm) | 1.5 (38) | 2.0 (50) | ASTM D374 |
| Tensile Strength, kpsi (MPa) | 34 (234) | 30 (207) | ASTM D882 |
| Elongation, % | 60 | 63 | ASTM D882 |
| Tensile Modulus, kpsi (GPa) | 520 (3.6) | 430 (3.0) | ASTM D882 |
| Density, g/cc | 1.69 | 1.83 | ASTM D1505 |
| Yield, ft²/lb (m²/kg) | 79.7 (16.3) | 56.8 (11.6) | — |
Electrical Properties
| Property | 150FWR019 | 200FWR919 | Test Method |
| Dielectric Strength, V/mil (kV/mm) | 4500 (177) | 5000 (197) | ASTM D149 |
| Dielectric Constant @ 1 kHz | — | 2.7 | ASTM D150 |
| Dissipation Factor @ 1 kHz | — | 0.0013 | ASTM D150 |
| Volume Resistivity, ohm-cm | — | 2.30 x 10¹⁷ | ASTM D257 |
Dielectric constant, dissipation factor, and volume resistivity are listed for 200FWR919 only per the source TDS.
Thermal Properties (Polyimide Film Data)
| Property | Typical Value | Test Method |
| UL Electrical RTI, °C | 240 | UL746B |
| UL Mechanical RTI, °C | 200 | UL746B |
Flame & Fire Performance
| Property | Typical Value | Test Method |
| Flammability | V-0 | UL-94 |
Chemical Properties (Polyimide Film Data)
| Property | Typical Value | Test Method |
| Moisture Absorption, 100% RH, % | 2.2 | ASTM D570 |
| Water Vapor Permeability, g/m²/day | 8.4 | ASTM E96 |
| Hygroscopic Coefficient of Expansion, ppm/%RH | 9 | — |
This table reflects polyimide film data only, per the source TDS.
Compliance
- UL-94 — Compliant (V-0)
- UL746B — UL Electrical RTI 240°C
- UL746B — UL Mechanical RTI 200°C
- Magnet wire insulation in motors and generators operating in high-humidity environments where hydrolysis resistance is critical
- Rail, automotive, and mining traction motor winding insulation requiring UL-rated thermal performance and moisture resistance
- Wind and hydro generator coil insulation in wet environments where standard polyimide moisture absorption limits service life
- ESP motor winding insulation in downhole applications where insulation is exposed to water and elevated temperature
- Aerospace specialty wire insulation requiring a hydrolysis-resistant, heat-fusible polyimide-FEP composite
Common industries: electric motor manufacturing, magnet wire fabrication, power generation, rail and automotive traction, oil and gas, aerospace.
Kapton® FWR is a heat-fusible composite insulation film designed for magnet wire applications where hydrolysis resistance is a critical requirement — particularly in high-humidity environments, sealed motor constructions, and applications where the insulation is exposed to moisture at elevated temperatures over an extended service life.
The film uses an FEP fluoropolymer layer on the polyimide core to provide heat fusibility and can be processed on most tape wrapping machines using induction or radiant heat fusing, with the same general approach as other Kapton® FN-family films, though wire wrapping and sealing conditions may require adjustment to account for FWR’s higher modulus and lower water vapor permeability.
Both constructions — 150FWR019 (1.5 mil, single-sided FEP) and 200FWR919 (1.0 mil polyimide with 0.5 mil FEP on each side) — are available.
Moisture absorption at 100% RH is 2.2% (polyimide film data), and water vapor permeability is 8.4 g/m²/day — notably lower than standard Kapton® FN composite films, making FWR a better barrier in wet environments. Hygroscopic coefficient of expansion is 9 ppm/%RH. Tensile modulus of 520 kpsi (3.6 GPa) for 150FWR019 and 430 kpsi (3.0 GPa) for 200FWR919 are both higher than equivalent Kapton® FN constructions.
Dielectric constant and dissipation factor are listed for the 200FWR919 construction only (2.7 and 0.0013 respectively at 1 kHz); volume resistivity is 2.30 x 10¹⁷ ohm-cm.
Compliant with UL 94 V-0. UL Electrical RTI 240°C and UL Mechanical RTI 200°C per UL746B.
What differentiates Kapton® FWR from Kapton® FN and Kapton® 150FWN019?
Kapton® FWR is specifically formulated for significantly improved hydrolysis resistance versus other commonly used polyimide insulation materials, including Kapton® FN. Its higher modulus (520 kpsi / 3.6 GPa for 150FWR019 vs. the FN family) and lower water vapor permeability (8.4 g/m²/day) make it superior as a moisture barrier. Compared to 150FWN019, FWR is selected when hydrolysis resistance — not scrape abrasion resistance or low friction — is the primary requirement.
Why does dielectric strength matter for magnet wire insulation selection?
Dielectric strength defines how much voltage the insulation withstands before breakdown between adjacent conductors or to the stator core. Kapton® FWR provides 4500–5000 V/mil (177–197 kV/mm) depending on construction, supporting the voltage withstand requirements of industrial motor and generator insulation systems across the available gauge range.
What is the service temperature rating for Kapton® FWR?
Kapton® FWR carries a UL Electrical RTI of 240°C and a UL Mechanical RTI of 200°C, both per UL746B.
Is Kapton® FWR suitable for regulated environments?
Yes. Kapton® FWR is rated UL 94 V-0 and carries UL Electrical RTI 240°C and UL Mechanical RTI 200°C per UL746B.
How should Kapton® FWR be specified?
Specify construction (150FWR019 for 1.5 mil or 200FWR919 for 2.0 mil), compliance requirements (UL 94 V-0, UL746B RTI ratings), fusing method (induction or radiant heat), overlap requirements, dimensional tolerances, and finished format (slit roll for tape wrapping or fabricated component).
