Applications
Automotive & Motorcycle
Exhaust systems such as exhaust manifolds, and oil/fuel sealing for engine blocks and transmission cases.
Industrial, Construction & Agricultural Machinery
Case components around internal combustion engines and hydraulics of all kinds, from high-temperature, high-load points to low-temperature oil, fuel, and water applications.
EV & Emerging Applications
New applications, such as battery, inverter, and motor cases, that need both flame retardancy and sealing performance.
Challenges We Help Solve
Gaskets Sagging Under Exhaust-System Heat
Around exhaust manifolds and similar points under continuous high temperature and clamping load, stress relaxation (sagging) can lead to leaks.
Reliably Sealing Oil, Fuel & Antifreeze at Case Components
On engine blocks, transmission cases, and similar components, even on cast surfaces or under excessive load, you need stable sealing without lateral flow.
Flame Retardancy Now Required in EV & New Applications
Battery packs, ECU cases, and other components bring requirements different from conventional internal combustion engines: new sealing points that demand flame retardancy in addition to sealing performance.
Non-Metallic | Paper-Based Gaskets Without Metal, Sealing Oil & Fuel
A paper-based gasket material that contains no steel plate. This line puts the formulation and papermaking techniques rooted in washi papermaking to their most direct use. Choose according to where you need to seal, from Oil Sheet, an affordable option with excellent conformability, to BS Joint Sheet, which covers low to high surface pressure with a low stress-relaxation rate.
AF2000 (BS Joint Sheet)
A premium non-metallic grade for sealing lubricating oil and fuel oil at case components. Exhibits high swelling in oil, preventing surface-pressure loss from reduced clamping force or flange deformation. Low stress-relaxation rate and excellent durability.
- Application: Sealing lubricating oil and fuel oil at case components
- Thickness: 0.8 mm
- Operating temperature: -40 to 200°C / Operating surface pressure: 2-147 MPa
- Stress relaxation rate: 15% (21% at 150°C)
Oil Sheet No.500
Devised by our founder, Teruo Sekine, using a hand-papermaking method, the origin of our gasket materials. Especially resistant to oil and solvents, with an exceptionally uniform material structure. High tensile strength allows use even at high surface pressure, with excellent durability.
- Application: Sealing water, oil, and fuel
- Thickness: 0.8 mm
- Operating temperature: -40 to 150°C
- Compression rate: 26% (recovery rate 40%) / Tensile strength: 24 MPa
Semi-Metallic | Sealing the Front Line of High Temperature & High Load
A gasket material for high temperature and high load, made by bonding steel plate to a paper-based sheet material. Steel Best withstands the high heat of exhaust systems, while Sisco Metal seals oil, fuel, and antifreeze at case components under high load. We choose between them according to the severity of the sealing point.
Steel Best (AF1810SB)
A sheet made of special heat-resistant fiber, inorganic reinforcement, and a small amount of synthetic rubber, pressed onto both sides of a double-sided hooked steel plate. High strength, excellent heat resistance, and a low stress-relaxation rate. Suited to exhaust-system points that need strength at high temperature.
- Application: Exhaust-system points requiring strength at high temperature
- Structure: Double-sided hooked steel plate + sheet (AF1800), pressed together
- Standard operating temperature: -40 to 500°C
- Stress relaxation rate: 13% (21% at 200°C) / Tensile strength: 53 MPa
Sisco Metal (ES020)
A sheet containing oil-resistant synthetic rubber bonded to both sides of a steel (SPCC) core. With a facing material of 75μm or more per side, it excellently absorbs casting-surface porosity and roughness on the mating face, and resists lateral flow even under excessive load. Seals oil and fuel at case components under high load.
- Application: Oil and fuel at case components under high load
- Structure: Steel (SPCC) core + beater sheet, bonded
- Standard operating temperature: -40 to 300°C
- Stress relaxation rate: 14% (150°C × 22h) / Facing material: 75μm or more per side
Steel Best × Sisco Metal | Quick Selection Guide
| Property | Steel Best (AF1810SB) | Sisco Metal (ES020) |
|---|---|---|
| Primary application | High-temperature exhaust systems (manifolds) | Oil/fuel at case components + high-load points |
| Structure | Double-sided hooked steel plate + sheet (AF1800), pressed | Steel (SPCC) core + beater sheet, bonded |
| Standard operating temperature | -40–500°C | -40–300°C |
| Compression/Recovery rate | 11% / 55% | 7% / 58% |
| Stress relaxation rate (150°C×22h) | 13% (21% at 200°C) | 14% |
| Strengths | High-temp range, strength (53 MPa tensile), heat resistance | Casting-porosity absorption, resistance to lateral flow, oil resistance |
*The figures above are representative values, not guaranteed specification values. Please refer to each catalog for details.
For the Next Generation | Flame-Retardant Gaskets for EV Components
We are extending the sealing technology we built in internal combustion engines to EVs, the next frontier. For applications such as battery packs and ECU cases, where flame retardancy is required in addition to sealing performance, we have developed a washi-born flame-retardant gasket material (Japanese Patent No. 7800953 / Japanese Unexamined Patent Application Publication No. 2026-75310, “Flame-Retardant Gasket Material, Secondary Battery Case, and ECU Case”). Drawing on the formulation freedom of paper, capable of taking on almost any property, we design materials tailored to your requirements.
Flame Retardancy (UL94 V-0 Equivalent)
Special heat-resistant fiber and inorganic reinforcement compounded with a flame retardant. Self-extinguishes on contact with flame and goes out when the flame source is removed. Suited to battery, inverter, and motor cases.
High Tensile Strength & Durability
Very high tensile strength and excellent durability, built directly on the formulation and papermaking sealing technology behind our roughly 80% domestic market share.
Low Stress-Relaxation Rate
A low stress-relaxation rate, with particular resistance to sagging under high temperature and high surface pressure, supporting long-term reliability of fastened joints.
Self-extinguishing on contact with flame. Our flame-retardant gasket does not spread fire when exposed to flame, and extinguishes once the flame source is removed. Suited to applications where EV component safety requirements apply.
Flame-Retardant Gasket | Properties
| Property | Value | Notes |
|---|---|---|
| Thickness | 0.5 mm (0.3-2.0 mm available) | Representative value |
| Compression/Recovery rate | 8% / 60% | P=34.5MPa |
| Tensile strength | 24 MPa | — |
| Stress relaxation rate | 15% | 100℃×22h |
| Flame retardancy | V-0 equivalent | UL-94 |
*The figures above are representative values, not guaranteed specification values. Product thickness from 0.3 to 2.0 mm is available.
Why Choose Sekine Seal Industrial
Formulation Expertise to Design the Material Itself
We’ve built a database of formulations combining special fibers, reinforcement materials, and synthetic rubber, tailoring materials from non-metallic to semi-metallic to flame-retardant, matched to where they need to seal.
~80% Domestic Share in Beater-Sheet Gaskets
The gasket materials we have made since our founding hold roughly 80% domestic share in beater-sheet gaskets, trust built with around 170 automotive and industrial machinery manufacturers.
1,300 Years of Papermaking Technology & Integrated Operations
Built on papermaking technology inherited from Hosokawa-shi, a UNESCO Intangible Cultural Heritage, offering an integrated approach from R&D through production.
Our Process
Contact Us
Start by reaching out through our contact form. We welcome everything from new product development and joint development inquiries to questions about existing products.
Selecting an Existing Product or Developing a New Formulation
Based on your requirements, application, function, budget, lead time, and more, we propose the specification we believe fits best.
Lab Evaluation
We run a lab evaluation to confirm whether a material meeting your requirements can be manufactured.
Production-Line Trial
We produce trial samples using actual production equipment.
Mass Production & Delivery
We begin mass production and deliver to you.
Feel Free to Discuss Your Sealing Material & Gasket Needs
High temperatures in exhaust systems, high loads at case components, flame-retardancy requirements for EVs: we propose the optimal material for the conditions at your sealing point.
Frequently Asked Questions
Q. How should I choose between non-metallic and semi-metallic?
As a general guide, choose non-metallic (AF2000, Oil Sheet No.500) for relatively low-temperature oil, fuel, antifreeze, and water applications, and semi-metallic (Steel Best, Sisco Metal) for high exhaust-system temperatures or high-load case components. Tell us about your operating environment and we’ll recommend the best-fit grade.
Q. What is the difference between Steel Best and Sisco Metal?
Steel Best is designed for high-temperature exhaust systems, covering a range of -40 to 500°C with a low stress-relaxation rate that resists sagging. Sisco Metal is designed for case components, with good absorption of casting-surface porosity on the mating face and resistance to lateral flow even under excessive load.
Q. Can thickness and size be customized?
Yes. We can adjust formulation, thickness, and size. Please contact us with the conditions of your sealing point.
Q. Can you provide samples or small-lot trial production?
Yes. We also support trial production at the development and evaluation stage, so please feel free to contact us.
Q. Can I also discuss flame-retardant gaskets for EV components?
Yes. For applications such as battery, inverter, and motor cases, where you need both flame retardancy (UL94 V-0 equivalent) and sealing performance, we’re happy to discuss from the development stage.
Q. Do you comply with environmental regulations such as RoHS and REACH?
Compliance varies by product and grade. Please check with us for details when you contact us.