Kapton® HPP-ST Two-Sided Treated Polyimide Film
Kapton® HPP-ST is a two-sided, surface-treated polyimide film offering the same balance of physical, chemical, and electrical properties as general purpose Kapton® HN, with superior dimensional stability and excellent adhesion to most adhesive systems. Shrinkage at 150°C is 0.03% across all gauges, making it the preferred choice where low shrinkage and superior adhesion are critical. The film carries a UL-94 94V0 flammability rating and is available in 1–5 mil gauges.
Key Properties
- Tensile Strength: 1–3 mil: 34 kpsi (234 MPa); 1 & 5 mil: 33.5 kpsi (231 MPa) — ASTM D-882-91
- Elongation: 1–2 mil: 72%; 3 mil: 78%; 5 mil: 82% — ASTM D-882-91
- Dielectric Strength: 1 mil: 303 V/µm (7,700 V/mil); 5 mil: 154 V/µm (3,900 V/mil) — ASTM D-149-91
- Service Temperature Range: Wide temperature range; same as general purpose Kapton® HN
- Available Thickness Range: 1–5 mil (25–125 µm)
- Density: 1.42 g/cc — ASTM D-1505-90
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- Specifications
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Physical Properties
| Property | Value | Test Method |
| Tensile Strength | 1 mil: 33.5 kpsi (231 MPa); 2 mil: 34 kpsi (234 MPa); 3 mil: 34 kpsi (234 MPa); 5 mil: 33.5 kpsi (231 MPa) | ASTM D-882-91 |
| Elongation | 1 mil: 72%; 2 mil: 72%; 3 mil: 78%; 5 mil: 82% | ASTM D-882-91 |
| Tensile Modulus | 400 kpsi (2.8 GPa), all gauges | ASTM D-882-91 |
| Adhesion* | 10 pli (1.8 N/mm), all gauges | IPC-TM-650 Method 2.4.9 |
| Density | 1.42 g/cc, all gauges | ASTM D-1505-90 |
| MIT Folding Endurance | 1 mil: 285,000; 2 mil: 55,000; 3 mil: 6,000; 5 mil: 3,000 cycles | ASTM D-2176-89 |
| Tear Strength, propagating (Elmendorf) | 1 mil: 0.07 N; 2 mil: 0.21 N; 3 mil: 0.38 N; 5 mil: 0.58 N | ASTM D-1922-89 |
| Tear Strength, initial (Graves) | 1 mil: 7.2 N; 2 mil: 16.3 N; 3 mil: 26.3 N; 5 mil: 46.9 N | ASTM D-1004-90 |
| Flammability | 94V0, all gauges | UL-94 |
| Shrinkage, 30 min at 150°C | 0.03%, all gauges | IPC-TM-650 Method 2.2.4A |
| Limiting Oxygen Index | 1 mil: 37%; 2 mil: 43%; 3 mil: 46%; 5 mil: 45% | ASTM D-2863-87 |
| Yield Point at 3% (23°C) | 69 MPa (10,000 psi), all gauges | ASTM D-882-91 |
| Yield Point at 3% (200°C) | 41 MPa (6,000 psi), all gauges | ASTM D-882-91 |
| Stress to Produce 5% Elongation (23°C) | 90 MPa (13,000 psi), all gauges | ASTM D-882-91 |
| Stress to Produce 5% Elongation (200°C) | 62 MPa (9,000 psi), all gauges | ASTM D-882-91 |
| Impact Strength at 23°C | 78 N·cm (0.58 ft·lb), all gauges | Qnity Pneumatic Impact Test |
| Coefficient of Friction, kinetic (film-to-film) | 0.48, all gauges | ASTM D-1894-90 |
| Coefficient of Friction, static (film-to-film) | 0.63, all gauges | ASTM D-1894-90 |
| Refractive Index (sodium D line) | 1.70, all gauges | ASTM D-542-90 |
| Poisson’s Ratio | 0.34, all gauges | Avg. three samples, elongated at 5%, 7%, 10% |
| Low Temperature Flex Life | Pass, all gauges | IPC-TM-650, Method 2.6.18 |
*Adhesion measured with acrylic adhesive to 1 oz. copper.
Thermal Properties
| Property | Value | Test Method |
| Melting Point | None | ASTM E-794-85 (1989) |
| Thermal Coefficient of Linear Expansion | 20 ppm/°C (11 ppm/°F) | ASTM D-696-91; -14 to 38°C (7 to 100°F) |
| Coefficient of Thermal Conductivity | 0.20 W/m·K (4.8 x 10⁻⁴ cal/sec-cm-°C) | ASTM D5470; 296 K (23°C) |
| Specific Heat | 1.09 J/g·K (0.261 cal/g·°C) | Differential calorimetry |
| Heat Sealability | Not heat sealable | — |
| Solder Float | Pass | IPC-TM-650, Method 2.4.13A |
| Smoke Generation | Dm = <1 | NFPA-258; NBS smoke chamber |
| Glass Transition Temperature (Tg) | A second order transition occurs between 360°C (680°F) and 410°C (770°F), assumed to be Tg; different measurement techniques produce different results within this range | — |
Electrical Properties (at 23°C / 73°F)
| Property | Value | Test Method |
| Dielectric Strength | 1 mil: 303 V/µm (7,700 V/mil); 2 mil: 240 V/µm (6,100 V/mil); 3 mil: 201 V/µm (5,100 V/mil); 5 mil: 154 V/µm (3,900 V/mil) | ASTM D-149-91; 60 Hz, 1/4 in electrodes, 500 V/sec rise |
| Dielectric Constant | 1–2 mil: 3.4; 3–5 mil: 3.5 | ASTM D-150-92; 1 kHz |
| Dissipation Factor | 1 mil: 0.0018; 2–3 mil: 0.0020; 5 mil: 0.0026 | ASTM D-150-92; 1 kHz |
| Volume Resistivity | 1–2 mil: 1.5 x 10¹⁷ Ω·cm; 3 mil: 1.4 x 10¹⁷ Ω·cm; 5 mil: 1.0 x 10¹⁷ Ω·cm | ASTM D-257-91 |
Thermal Coefficient of Expansion — 25 µm (1 mil), Thermally Exposed
| Temperature Range, °C (°F) | ppm/°C | Test Method |
| 30–100 (86–212) | 17 | — |
| 100–200 (212–392) | 32 | — |
| 200–300 (392–572) | 40 | — |
| 300–400 (572–752) | 44 | — |
| 30–400 (86–752) | 34 | — |
Compliance
- ASTM D-5213 (Type 1, Item A) — Compliant
- UL-94 — Compliant (94V0, all gauges)
- Adhesive-laminated flexible circuit substrates requiring low shrinkage and superior bond retention
- PCB stencil and screen printing carrier films where dimensional accuracy under thermal cycling is critical
- Insulation tubing and wrapping for electronic assemblies requiring stable adhesive interfaces
- Electronic component packaging requiring a treated film surface for reliable adhesive lamination
- Flexible constructions combining polyimide with pressure-sensitive or thermally activated adhesives
Common industries: electronics, printed circuit manufacturing, flexible circuit fabrication, electrical equipment manufacturing.
Kapton® HPP-ST is a high performance variant of the Kapton® polyimide film family, distinguished by its two-sided surface treatment that delivers superior adhesion with most adhesive systems — including acrylic adhesives to copper. It is designed for applications where dimensional stability under thermal exposure is critical: shrinkage at 150°C is 0.03% across all gauges, substantially lower than the standard HN film.
All other core properties — tensile strength, modulus, density, and electrical characteristics — match those of general purpose Kapton® HN.
The film passes low-temperature flex testing per IPC-TM-650 Method 2.6.18, passes solder float per IPC-TM-650 Method 2.4.13A, and generates minimal smoke (Dm = <1, NFPA-258). It is rated 94V0 across all gauges per UL-94. The glass transition temperature is assumed to occur between 360°C (680°F) and 410°C (770°F); different measurement techniques produce different results within this range.
Compliant with ASTM D-5213 (Type 1, Item A) and rated UL-94 94V0.
What differentiates Kapton® HPP-ST from standard Kapton® HN?
Kapton® HPP-ST has a two-sided surface treatment that delivers adhesion of 10 pli (1.8 N/mm) to copper via acrylic adhesive — a performance level not available with untreated HN. Additionally, shrinkage at 150°C is 0.03% for HPP-ST versus 0.17% for HN, making HPP-ST significantly more dimensionally stable under thermal exposure while retaining identical tensile, modulus, and electrical characteristics.
Why does tensile strength matter for polyimide film selection?
Tensile strength governs how the film behaves under the mechanical stresses of laminating, die-cutting, and end-use flexing. Kapton® HPP-ST maintains 33.5–34 kpsi (231–234 MPa) across all gauges at room temperature, ensuring consistent handling and processing performance regardless of gauge selection.
What is the service temperature range for Kapton® HPP-ST?
Kapton® HPP-ST offers the same wide temperature performance as general purpose Kapton® HN. The film is not heat sealable, passes solder float testing per IPC-TM-650 Method 2.4.13A, and has no melting point per ASTM E-794-85. Glass transition is assumed to occur between 360°C (680°F) and 410°C (770°F).
Is Kapton® HPP-ST suitable for flame-rated environments?
Yes. Kapton® HPP-ST is rated 94V0 across all gauges per UL-94, and is compliant with ASTM D-5213 (Type 1, Item A).
How should Kapton® HPP-ST be specified?
Specify grade (Kapton® HPP-ST), thickness in mil or µm, compliance requirements (ASTM D-5213 Type 1 Item A, UL-94 94V0), adhesive system if laminated, dimensional tolerances, and finished format (slit roll, sheet, die-cut, or laminated construction).
