High Temperature Resistant Rubber Seal | Material Comparison

For industrial sealing applications above 150°C, silicone rubber (VMQ/PVMQ) and fluorocarbon rubber (FKM) dominate the high temperature resistant rubber seal market, with continuous service ratings of 200°C and 230°C respectively—though selection depends on whether your environment involves oil contact, steam exposure, or dry heat cycling.

Comparative Thermal Performance: Silicone vs. FKM vs. EPDM

The table below presents verified thermal aging data from 1000-hour exposure tests per ASTM D573:

Material	Continuous Temp. (°C)	Peak Temp. (°C)	Tensile Retention @ 200°C/1000h	Compression Set @ 200°C/70h
Silicone (VMQ)	200	250	78%	22–28%
Fluorosilicone (FVMQ)	200	230	74%	25–32%
Fluorocarbon (FKM)	230	280	85%	18–24%
EPDM (peroxide-cured)	150	180	52%	45–55%
HNBR	150	165	68%	35–42%

FKM offers superior tensile retention and lower compression set at extreme temperatures, but silicone remains the cost-effective choice for non-oil environments requiring flexibility retention below -50°C.

Mechanical Properties Under Thermal Stress

Tensile Strength and Elongation Degradation

Post-aging mechanical performance dictates seal longevity in dynamic applications:

• Silicone VMQ-70: Initial tensile 9.5 MPa, 450% elongation → After 2000h @ 200°C: 7.2 MPa, 280% elongation
• FKM Viton A: Initial tensile 12.0 MPa, 250% elongation → After 2000h @ 230°C: 10.8 MPa, 190% elongation
• FVMQ: Initial tensile 8.0 MPa, 300% elongation → After 2000h @ 200°C: 6.1 MPa, 210% elongation

Applications involving repeated compression cycles (door seals, hatch gaskets) require minimum 5.0 MPa tensile retention to prevent tearing at mounting points.

Compression Set Performance

Compression set percentage (ASTM D395 Method B) determines seal recovery after prolonged clamping:

• FKM at 200°C/70h: 18–24% (excellent)
• Silicone at 200°C/70h: 22–28% (good)
• EPDM at 150°C/70h: 45–55% (marginal for high-temp)

Seals exceeding 35% compression set show measurable leak rates in gasketing applications after 6 months of continuous clamping at operational temperature.

Chemical Resistance at Elevated Temperature

Oil and Fuel Resistance

Volume swell after 168h immersion (ASTM D471) at 150°C:

Fluid	Silicone VMQ	Fluorosilicone FVMQ	FKM	HNBR
IRM 903 Oil	+180% (failure)	+18%	+8%	+12%
Diesel Fuel	+220% (failure)	+22%	+6%	+15%
Hydraulic Fluid (HFD)	+95%	+15%	+10%	+9%
Biodiesel B20	+140%	+28%	+12%	+18%

Standard silicone swells catastrophically in petroleum environments. FVMQ bridges the gap at 2.5× the material cost of VMQ. FKM remains the reference standard for automotive and aerospace fuel seals.

Acid and Alkali Resistance

Chemical process sealing requires resistance to both thermal and chemical attack. Hardness change (Shore A points) after 7 days at 120°C:

• 30% H₂SO₄: FKM +3, Silicone +2, EPDM +8
• 50% NaOH: EPDM -1, Silicone +4, FKM +6
• 98% Acetic Acid: Silicone +5, FKM +9, EPDM +15

EPDM excels in alkaline steam environments (caustic washdown systems), while FKM and silicone divide acid exposure applications based on concentration and temperature.

Low-Temperature Flexibility: Critical Selection Factor

Many high-temperature seals fail during cold-start conditions. TR-10 cold stiffening temperature (ASTM D1329):

• Silicone VMQ: -55°C to -65°C
• Fluorosilicone FVMQ: -45°C to -50°C
• FKM standard grades: -15°C to -25°C
• FKM low-temp grades (GFLT): -35°C to -40°C
• EPDM: -45°C to -50°C

Outdoor enclosures and cold-storage seals cycling between -40°C and +180°C mandate silicone or specialty FKM compounds, adding 40–60% to material costs.

Production Tolerances and Quality Control Parameters

Extrusion Tolerance Standards

Hunan Zhouxin maintains the following dimensional tolerances for high-temperature seal extrusions:

• Cross-section dimensions: ±0.15 mm (0–5 mm width), ±0.25 mm (5–15 mm width)
• Durometer: ±3 Shore A (batch consistency)
• Length tolerance: ±2 mm per meter (straight extrusions), ±1.5% (coiled)
• Corner radius: ±0.10 mm on vulcanized corners

Critical aerospace and semiconductor applications may specify ±0.08 mm on seal lips, requiring post-extrusion precision grinding.

Thermal Aging Verification

All production batches undergo accelerated aging verification:

• 168 hours @ maximum rated temperature
• Tensile/elongation must remain ≥70% of datasheet values
• Compression set ≤1.2× datasheet maximum
• Visual inspection for cracking, surface chalking, or delamination

Certification packages include stress-strain curves and DSC thermograms upon request for material lot traceability.

Application-Specific Material Selection Guide

Oven door seals (bakery, industrial ovens): Silicone 60–70 Shore A, continuous 200°C, FDA-compliant grades for food contact

Automotive turbocharger gaskets: FKM 75–80 Shore A, oil-resistant, peak 280°C intermittent

Steam autoclave door seals: EPDM 65 Shore A or silicone 70 Shore A, steam-resistant formulations, 150°C continuous

Aerospace engine bay seals: FKM low-compression-set grades, MIL-R-83248 or AMS 7276 specification

Chemical reactor manway gaskets: FKM or FFKM (perfluoroelastomer) depending on chemical matrix, 200–230°C

Cleanroom pass-through seals: Silicone 50 Shore A, low outgassing per ASTM E595 (<1.0% TML)

OEM/ODM Customization Capabilities

Hunan Zhouxin Sealing Technology offers compound customization for project-specific requirements:

• Custom durometer blending: 40–90 Shore A in 5-point increments
• Color matching: Pantone/RAL references (added pigments may affect thermal stability by 5–10°C)
• Co-extrusion: Dense skin over sponge core for improved compression-deflection curves
• Insert molding: Metal or fabric reinforcement for high-pressure applications
• Adhesive backing: PSA tapes rated to 150°C (silicone-based) or 120°C (acrylic-based)

Minimum development quantity: 500 kg per compound variant. Mold tooling lead time: 15–20 business days for standard profiles, 25–30 days for complex multi-cavity dies.

Frequently Asked Questions

Q: What is your minimum order quantity for FKM high-temperature seals? A: 200 meters per profile for stock extrusions; 500 kg (approximately 800–1200 meters depending on cross-section) for custom compounds. Silicone VMQ has lower MOQ at 100 meters for standard 60/70 Shore A grades.

Q: What lead time should we expect for a custom silicone extrusion with ±0.10 mm tolerance? A: 18–22 business days after drawing approval: 5 days compound formulation and testing, 3 days tooling adjustment, 7–10 days production and QC, 3–4 days precision inspection and packaging. Air freight adds 4–6 days to major ports.

Q: Do you provide material certifications for high-temperature aging performance? A: Yes. Each production lot includes a C of A (Certificate of Analysis) with tensile/elongation data, compression set results, and thermal aging verification per ASTM D573. FDA compliance letters available for food-grade silicone. RoHS/REACH declarations standard.

Q: What packing methods prevent deformation during international shipping? A: Straight lengths up to 6 m: cardboard tube core, PE film wrap, plywood crate. Coiled lengths: 300–500 mm diameter coils, individually wrapped, corrugated carton with corner protectors. Fragile profiles ship in custom foam inserts. All shipments include desiccant packs.

Q: Can we receive pre-production samples with actual production tooling? A: First-article samples (3–5 meters) produced on production dies are provided within 10 business days after tooling completion. Sample cost is waived for orders exceeding 1000 meters or USD $3,000. Samples ship via DHL/FedEx with dimensional inspection report.

Technical Specification Summary

Parameter	Silicone VMQ	Fluorosilicone FVMQ	FKM Viton	EPDM Peroxide
Hardness Range	40–80 Shore A	50–75 Shore A	60–90 Shore A	50–80 Shore A
Tensile Strength	8–10 MPa	7–9 MPa	10–15 MPa	10–12 MPa
Elongation at Break	400–600%	250–400%	200–300%	300–500%
Continuous Service	200°C	200°C	230°C	150°C
Compression Set (200°C/70h)	22–28%	25–32%	18–24%	45–55% (@ 150°C)
Low Temp. Flexibility	-60°C	-50°C	-25°C (-40°C GFLT)	-50°C
Oil Resistance	Poor	Good	Excellent	Poor
Cost Index	1.0×	2.5×	3.5–4.0×	0.7×

Send your CAD drawing and operating environment specifications (temperature range, chemical exposure, compression requirements) to receive a material recommendation and 24-hour quotation with MOQ and tooling costs.