Graphite Composite Plate_OTHER PLASTIC PRODUCTS-Hansa seal

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Graphite Composite Plate

Graphite Composite Plate Professional Profile

Material Definition

Graphite composite plate is a sheet material formed by using flexible graphite as the base functional unit and metal or non-metal materials as the structural reinforcement unit through mechanical pressing, bonding, or lamination composite processes. Its core component is flexible graphite coil, produced from high-purity flake graphite through chemical treatment and high-temperature expansion, which is then compressed and composited with reinforcement materials such as perforated/tanged metal sheets (Stainless Steel 304/316, tin-plated steel, carbon steel), flat metal foils, wire mesh, fiberglass, or polyester film. It is primarily categorized into tanged mechanical interlocking type and bonding type.

Main production methods include:

1. Tanged Sheet Composite: A 0.05-0.25mm metal sheet is perforated (tanged) and then mechanically interlocked with flexible graphite coil under pressure. The graphite embeds into the metal perforations, forming an interlocked structure with high bond strength, suitable for high-pressure dynamic sealing.

2. Flat Sheet Composite: Metal foil and flexible graphite sheet are laminated using an adhesive. This offers high surface flatness and is suitable for low-pressure static sealing and large sheet size requirements.

3. Lay-up Molding: For low-fluidity materials like fine flake graphite, semi-cured thin sheets and reinforcing substrates are alternately layered and consolidated via vacuum hot pressing. This allows precise control of component content and sheet thickness.

4. Multi-layer Laminated Composite: Consists of alternating layers of multi-layer stainless steel cores and high-purity anti-oxidant flexible graphite thin sheets, fused through proprietary processes to form high-strength laminates with excellent load-bearing characteristics and low leakage rates.

Core Performance Advantages

1. Extreme Temperature Dual-Domain Adaptability

Long-term service temperature in air: -200°C to 650°C; in non-oxidizing media: withstands -240°C to 3000°C ultra-high temperature. Extreme temperature resistance significantly surpasses fluoroplastics and traditional rubber materials.

Excellent thermal shock resistance; direct transfer from -200°C cold state to 600°C high-temperature conditions without embrittlement.

2. Full pH Range Chemical Resistance

Chemically inert to almost all acids, alkalis, salts, and organic solvents (pH 0-14). Only slight corrosion by high concentrations of strong oxidizing acids (e.g., concentrated nitric acid, hot concentrated sulfuric acid).

Completely free of organic binders; no aging, embrittlement, or hardening; service life comparable to the equipment itself.

3. Synergy of Metallic Strength and Graphite-grade Sealing

Overcomes strength limitations of pure graphite sheets: Tensile strength of tanged composite sheets ≥ 4.0-5.0 MPa; multi-layer high-pressure laminates withstand pressures up to 250 Bar (PN40 class), suitable for high-temperature and high-pressure conditions.

Retains excellent compression recovery of flexible graphite: compressibility 15-55%, recovery ≥ 9-20%, offering strong compensation for flange surface irregularities.

4. Integration of Thermal Conduction and Self-lubrication Functions

Thermal conductivity along the plane direction: 25-150 W/m·K (depending on density and type), enabling rapid hot spot dissipation; through-plane thermal conductivity: 5-10 W/m·K, providing design flexibility for both heat dissipation and insulation.

Solid self-lubricating properties, low friction coefficient, no cold flow, creep relaxation rate ≤ 10%.

5. Nuclear Purity and Low Leachables

Nuclear grade products: Sulfur content ≤ 1200 ppm, Chlorine content ≤ 30 ppm, meeting irradiation requirements for nuclear power plant valves and main pump seals.

Optional boron-modified type (Boron content ≥ 3%) offering neutron shielding capability.

6. Processing Convenience and Edge Protection

Easily cut and stamped; can be processed into basic types, inner edge wrapped, outer edge wrapped, inner/outer edge wrapped, etc. Stainless steel edging preserves graphite's excellent performance while preventing medium erosion, facilitating installation/removal, and improving pressure rating.

Material Types and Specification System

Type	Structural Features	Common Thickness Range (mm)	Width/Size (mm)	Main Production Method	Main Application Scenarios
Tanged Metal Composite	0.1-0.25mm metal core, perforated & mechanically interlocked with graphite	0.8 - 3.2	1000×1000, 1500×1500, 1524×1524	Tanged Roller Compounding	Chemical reactors, high-pressure valves, engine head gaskets
Flat Sheet Composite	0.05mm metal foil bonded with graphite via adhesive	0.8 - 3.2	1000×1000, 1500×1500	Lamination Bonding	Power plant condensers, low-pressure flanges, instrument connections
Wire Mesh Reinforced	Stainless/carbon steel woven mesh embedded in graphite matrix	1.5 - 4.0	1000×1500 (custom)	Compression Composite	Heat exchangers, marine piping, vibration-prone seals
Non-metal Composite	Reinforcement layer like fiberglass cloth/polyester film	1.0 - 3.0	1000×1200 (custom)	Adhesive Lamination	Electronic/electrical insulation gaskets, low conductivity seals
Multi-layer High-Pressure Laminates	Alternating layers of stainless steel foil and high-purity graphite	1.5 - 6.0 (custom)	1500×1500 (custom)	Proprietary Fusion Lamination	Refinery high-pressure flanges, NPP reactor coolant pumps, high-pressure HX
Fine Flake Graphite Composite	Phenolic resin bonded fine flake graphite, slurry/lay-up molded	1.0 - 5.0	Custom	Slurry + Hot Press / Lay-up + Hot Press	Low-cost sealing gaskets, automotive parts, general industry

Technical Parameters and Performance Indicators

Physical & Mechanical Properties

Property	Typical Value/Range	Standard/Reference
Density (g/cm³)	1.0 - 2.1 (post-composite)	GB/T 3521-2023
Tensile Strength (MPa)	4.0 - 15.0 (depends on reinforcement)	ASTM F152
Compressibility (%)	15 - 55	ASTM F36
Recovery (%)	9 - 20	ASTM F36
Stress Relaxation (%)	≤ 10	DIN 52913
Ash Content (%)	≤ 1.0 - 2.0	GB/T 3521
Sulfur Content (ppm)	≤ 1200 (lower for nuclear grade)	GB/T 43887-2024
Chlorine Content (ppm)	≤ 30 - 50	GB/T 43887-2024

Thermal & Electrical Properties

Property	Typical Value/Range	Standard/Reference
Service Temp (Air, °C)	-200 to 650	—
Service Temp (Non-oxidizing, °C)	-240 to 3000	—
Thermal Weight Loss (450°C, %)	≤ 0.5 - 1.0	ISO 1887
Thermal Weight Loss (600°C, %)	≤ 10 - 20	ISO 1887
Thermal Conductivity (∥, W/m·K)	25 - 150	ISO 22007
Thermal Conductivity (⊥, W/m·K)	5 - 10	ISO 22007
Volume Resistivity (μΩ·m)	5 - 10 (High-density conductive type)	GB/T 24525
Saturated Water Absorption (%)	< 2.0	ASTM D570

Typical Application Areas

Application Field	Specific Uses	Recommended Type	Key Requirements
Petroleum Refining	High-temp/pressure flanges, reactor manways, HX, valve packing	Tanged SS Composite, Multi-layer HP Laminate	Resists hydrocarbons, creep resistant @600℃, high recovery
Nuclear Power	NPP main pump seals, fuel transfer systems, boron shielding layers	Nuclear Grade Flexible Graphite Composite (Low S/Cl/Boron)	Radiation resistance, ultra-low leachables, neutron absorption
Automotive Industry	Head gaskets, intake/exhaust manifold gaskets, EGR cooler seals	Tanged Tin-plated Steel/Carbon Steel Composite	Resists high-temp combustion gas, vibration fatigue resistance
Chemical & Metallurgy	Strong corrosive media tanks, pickling line flanges, electrolytic cell seals	Flat SS Composite, Wire Mesh Reinforced	Full pH resistance, long-term temp resistance, non-stick
Electronics/Electrical	Thermal conductive insulation gaskets, EMI shielding gaskets	Fiberglass/Polyester Reinforced Composite	High thermal conductivity, low electrical conductivity, tight tolerances
Aerospace & Marine	Fuel system seals, seawater line gaskets, exhaust systems	Wire Mesh Reinforced/Tanged Composite	Salt spray resistance, thermal shock resistance, flame retardant
General Industry	Compressors, refrigeration units, vacuum pumps, sight glass seals	General Purpose Graphite Composite	Low leakage rate, easy install/removal, cost-effective

Processing, Joining & Installation Guide

1. Machining

Cutting: Use waterjet, circular shear, oscillating knife, or laser cutting (control HAZ). Die cutting recommended for batch gasket production; die clearance recommended at 5%-8% of sheet thickness.

Drilling/Hole-making: Use HSS drills, 118° point angle, cooling with compressed air to avoid dust clogging. For edge-wrapped sheets, drill before edging or use a trepanning tool.

2. Edging & Sealing Enhancement

Metal Edging: 304/316 stainless steel strip (0.1-0.2mm) completely covers the inner/outer edge using specialized edging machine. Prevents medium erosion of gasket body, improves pressure rating, and facilitates installation positioning.

Edging Form Selection: Inner edge wrap for strong corrosive media; Outer edge wrap for anti-stick high-viscosity media; Inner/Outer edge wrap for vacuum or pressure-fluctuating conditions.

3. Installation Key Points

Flange Face Preparation: Ensure flange face has no radial scratches, surface roughness Ra 3.2-6.3μm. Applying liquid sealant on graphite surface is strictly prohibited.

Bolt Pre-tensioning: Recommended to use torque wrench, tighten in 2-3 symmetrical passes. Graphite composite plate has very low cold flow tendency, but over-compression damages reinforcement skeleton; recommended pre-tightening stress: 30-50 MPa.

Static Electricity Protection: Pure graphite component is conductive. For flanges handling flammable media, ensure flange cross-bonding to prevent static accumulation due to gasket resistivity fluctuations.

Selection Decision Matrix

Application Scenario	Primary Performance Requirement	Recommended Plate Type	Key Considerations
High-temp/pressure Steam Lines	Ultra-low leakage rate, thermal shock resistance	Multi-layer Stainless Steel HP Laminate (RGS-HP Grade)	Verify temp ≥ 550℃, pressure class matches PN40
Strong Corrosive Chemical Plants	Full chemical resistance, high purity	Flat SS Composite Plate (316L Foil)	Prefer inner/outer edge wrap to avoid end-grain penetration
Engine Cylinder Seals	High-frequency vibration resistance, combustion gas resistance	Tanged Tin-plated Steel Composite Plate	Thickness tolerance ±0.05mm, density ≥ 1.2 g/cm³
NPP Nuclear Island Seals	Ultra-low sulfur/chlorine, radiation resistance	Nuclear Grade Flexible Graphite Composite Plate	Must comply with GB/T 43887-2024 nuclear grade standard
Must comply with GB/T 43887-2024 nuclear grade standard	Economy, ease of processing	Fine Flake Graphite Composite Plate	Control phenolic resin content to avoid high-temp embrittlement
Electronics Thermal Management	High thermal conductivity, electrical insulation	Fiberglass Reinforced Graphite Composite Plate	Thermal path design must differentiate in-plane vs through-plane

Industry Customized Solutions

High-Pressure Flange Seals for Integrated Refining Units

Requirement: Catalytic cracking, hydrocracking units; operating temp 500-650℃, pressure 10-25 MPa; media containing H₂S, H₂.

Solution: Multi-layer Stainless Steel/Graphite High-Pressure Laminate (Flexicarb® RGS-HP Grade); laminate structure effectively prevents high-pressure extrusion; bonded interfaces reduce permeation leakage.

Application: Hydrotreater reactor manways, high-pressure heat exchanger channel covers.

Sealing Systems for Generation IV Nuclear Reactors

Requirement: High-temperature gas-cooled reactors (HTGR), Helium medium, temp 800-950℃, neutron radiation resistance, ppt-level impurity leachables.

Solution: Boron-containing isostatically pressed graphite composite plate; matrix density ≥ 1.85 g/cm³; boron distribution uniformity ±0.3%; combines sealing and shielding functions.

Application: Control rod drive mechanism seals, fuel handling system seals.

Bipolar Plates for Hydrogen Fuel Cells

Requirement: High electrical conductivity (≥ 100 S/cm), ultra-low gas permeability (He leakage rate < 10⁻⁶ mbar·L/s), resistance to acidic wet environment.

Solution: High-density compression molded graphite plate (density 1.7-1.9 g/cm³); precision micro-channel machining; surface roughness Ra ≤ 3.2μm.

Application: PEM fuel cell stacks, flow battery stacks.

Salt Spray Resistant Seals for Marine & Offshore

Requirement: Seawater cooling systems, ballast tanks; resistance to chloride ion stress corrosion cracking (SCC).

Solution: 316L tanged sheet composite with HDS101 grade flexible graphite; full wrap edging using same material.

Application: Plate heat exchanger seals, stern tube seals.

Storage & Maintenance

Storage Conditions

Environment: Clean, dry, ventilated warehouse; relative humidity < 60%. Avoid mixing storage with oils/chemicals. Strictly prohibit outdoor storage; prevent water ingress causing graphite layer moisture absorption and metal insert rusting.

Stacking: Store flat on level pallets; stack height ≤ 0.8m. Die-cut finished gaskets are recommended for hanging storage or flat layered storage to avoid compression deformation.

Shelf Life: "First-in, first-out" recommended. If storage period exceeds 2 years, retest compressibility, recovery, sulfur, and chlorine content.

Usage & Maintenance

Cleaning: Residue on disassembled gaskets can be wiped with brass brush or alcohol. Soaking metal-edged graphite gaskets in strong acid/alkali for cleaning is prohibited.

Repair: Minor surface indentation may allow reuse (non-metal reinforced type only). Must replace if metal undergoes plastic deformation, or graphite layer shows severe powdering or delamination.

Oxidation Inspection: Under long-term high-temperature operation, inspect gasket edges per cycle for white oxidation powder (graphite oxidation product). Immediate replacement required if edge oxidation depth > 1.5mm or penetrates to metal insert.

Torque Re-tightening: For high-temperature flanges, torque re-tightening at ambient temperature is recommended 24-48 hours after startup to compensate for preload loss due to thermal expansion.

Development Trends

Technological Development Directions

Ultra-Purification & Nuclear Grade: Control of corrosive impurities (S, Cl, F) towards ppm levels and below to meet stringent requirements of nuclear power and semiconductor epitaxial equipment.

Multi-layer Structures & Functional Composites: Evolution from single-layer tanged sheets to multi-layer heterogeneous laminate structures, achieving unification of high-pressure resistance and micro-leakage sealing; development of multifunctional integrated composite plates (thermal/electrical conductivity, EMI shielding).

Low-Carbon & Low-Cost Manufacturing: Promote fine flake graphite lay-up molding process as alternative to pure flexible graphite coil composite, reducing raw material costs and graphitization energy consumption; research recycling technology for waste graphite seals.

Precision Forming & Near-Net Shape: Isostatic pressing graphite composite plate near-net shaping technology to reduce machining loss; micron-level micro-channel precision engraving technology to meet accuracy requirements for fuel cell bipolar plates.

Market Application Expansion

Hydrogen Full Industry Chain: Upstream electrolyzer hydrogen production seals, midstream storage/transport bottle valve linings, downstream fuel cell bipolar plates.

Semiconductor Thermal Management: Single crystal silicon ingot growth furnace insulation shields, ion implanter shielding components; replacing imported isostatic graphite.

Data Center Liquid Cooling: Immersion cooling fluid seals, high thermal conductivity cold plate interface materials.

Aerospace Thermal Protection: High thermal conductivity/low density composite plates for airborne electronic equipment heat dissipation, engine heat shields.

Graphite composite plate achieves a classic composite logic of "metal imparts strength + graphite imparts sealing and corrosion resistance," enabling its transition from traditional asbestos sealing materials to high-end static and dynamic sealing systems. As a non-replaceable fundamental sealing component for high-temperature and high-pressure conditions, it continues to play a core "industrial articular cartilage" role in key fields such as petrochemical equipment, nuclear island primary circuits, and new energy vehicle powertrain systems. Correct composite structure selection, precise edge protection, and standardized installation pre-tensioning are the three pillars ensuring its full lifecycle sealing reliability. Amid the global wave of energy transition and equipment high-end advancement, graphite composite plate is upgrading from a单纯 sealing gasket material to a multifunctional engineering plate integrating thermal management, conductive transmission, and nuclear shielding capabilities.

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Publisher：Hansa seal Pubtime：2026-02-13 10:27:00 Close