Custom Rubber Extrusion Service | OEM Material Specifications

For overseas buyers sourcing custom rubber extrusion service, the decisive factor is not the shape but the polymer matrix — tensile strength, compression set, and thermal aging dictate sealing performance over a 10-15 year lifecycle. Below are the material specifications we have validated through 15 years of production at our Hunan factory, with data drawn from ASTM D573, ASTM D395, and ISO 1817 testing protocols.

Elastomer Selection Matrix by Application Environment

Selecting the correct durometer and polymer compound for your custom rubber extrusion service begins with three parameters: operating temperature range, fluid contact, and required compression set resistance. The table below summarizes our standard compounds.

Material	Shore A Hardness	Tensile Strength (MPa)	Temperature Range (°C)	Compression Set 22h/70°C (%)	Ozone Resistance (ASTM D573)	Oil Resistance (ASTM #3, 70h/100°C)
EPDM 70A	70 ± 5	8.5 – 11.0	-40 to +150	≤ 25%	Excellent (no cracks @ 100 pphm x 40°C x 70h)	Poor (swell > 80%)
Silicone (VMQ) 60A	60 ± 5	6.5 – 8.5	-60 to +230	≤ 30%	Excellent	Fair (swell 20-40%)
NBR (Buna-N) 70A	70 ± 5	10.0 – 14.0	-30 to +120	≤ 20%	Fair	Excellent (swell < 10%)
SBR 65A	65 ± 5	7.0 – 9.0	-40 to +100	≤ 35%	Poor	Poor (swell > 100%)

In our Hunan factory experience, a project for offshore cabinet seals required NBR 70A with a tensile strength of 12.5 MPa and compression set below 18%. We achieved this by adjusting the sulfur vulcanization system and adding a specific anti-oxidant package — the seals passed 1,000 hours of ISO 1817 immersion in hydraulic oil with < 5% volume change.

Tensile Strength and Elongation Balance

For a custom rubber extrusion service, tensile strength alone is insufficient. The elongation at break and modulus at 100% elongation determine how the profile withstands installation stress and cyclic compression.

EPDM for Outdoor Sealing

• Tensile Strength: 8.5 – 11.0 MPa (ASTM D412)
• Elongation at Break: 300 – 450%
• Modulus at 100%: 2.0 – 3.5 MPa
• Application: door sealing strips for architectural openings, exposed to UV and ozone.

Silicone for High-Temperature Environments

• Tensile Strength: 6.5 – 8.5 MPa
• Elongation at Break: 400 – 600%
• Modulus at 100%: 1.5 – 2.5 MPa
• Application: silicone series for oven gaskets, LED lighting seals, and food-grade enclosures.

Compression Set and Long-Term Sealing Force

Compression set (ASTM D395 Method B) is the primary indicator of a seal’s ability to maintain a tight barrier over years. For a custom rubber extrusion service targeting industrial enclosures, we target ≤ 25% after 22 hours at 70°C for EPDM, and ≤ 20% for NBR.

Factors Influencing Compression Set

• Vulcanization crosslink density: Higher crosslink density reduces set.
• Filler loading: Excessive carbon black increases set.
• Post-cure treatment: A secondary oven bake at 150°C for 2 hours reduces set by 5-8%.

Thermal Aging and UV/Ozone Resistance

Thermal aging tests per ASTM D573 (70h at 100°C for EPDM, 70h at 200°C for silicone) measure retention of tensile strength and elongation. Our standard compounds retain > 85% of original tensile strength after aging.

Property	EPDM (70A)	Silicone (60A)	NBR (70A)
Tensile retention after thermal aging	88%	92%	82%
Elongation retention after thermal aging	80%	85%	75%
Ozone resistance (50 pphm, 40°C, 100h)	No cracks	No cracks	Cracks after 48h
UL 94 flame rating (option)	HB	V-0	HB

Extrusion Tolerance and Cross-Section Precision

Custom rubber extrusion service demands tight dimensional control. Our standard extrusion tolerance for profiles under 25 mm cross-section is ±0.30 mm; for profiles 25-50 mm, ±0.50 mm. Tighter tolerances (±0.15 mm) are achievable with post-extrusion vulcanization and die tuning.

Typical Tolerance Table

Profile Dimension (mm)	Standard Tolerance (mm)	Precision Tolerance (mm)
< 10	±0.20	±0.10
10 – 25	±0.30	±0.15
25 – 50	±0.50	±0.25
> 50	±0.80	±0.40

For cabinet seals requiring airtight performance, we recommend precision tolerance and 100% dimensional inspection.

Custom Compounding for Specialized Fluids

When your custom rubber extrusion service must resist acids, alkalis, or specific industrial fluids, the polymer matrix must be modified. We use ASTM D471 immersion testing (70h at 100°C) to validate swell and hardness change.

• EPDM: Excellent for dilute acids (5-10% H₂SO₄), alkalis (NaOH), and brake fluids (DOT 3/4). Swell < 5%.
• NBR: Suitable for mineral oils, diesel, and hydraulic fluids (ISO 32, 46, 68). Swell < 10%.
• Silicone: Not recommended for concentrated acids or steam; compatible with non-polar solvents only.

Frequently Asked Questions

What is the minimum order quantity (MOQ) for custom rubber extrusion service?

Our standard MOQ is 500 meters per profile design for standard EPDM and NBR compounds. For silicone or flame-retardant compounds, the MOQ is 300 meters due to raw material minimums. We can accommodate lower MOQs (100 meters) for prototype runs with a 50% tooling deposit.

What is the typical lead time from drawing approval to first shipment?

Lead time is 15-20 working days for standard EPDM profiles after final drawing approval and tooling confirmation. Silicone and specialty compounds require 20-25 working days. Urgent orders (7-10 days) are possible with expedited tooling and production scheduling.

What extrusion tolerance (±mm) can you guarantee?

Standard tolerance is ±0.30 mm for cross-section dimensions under 25 mm, and ±0.50 mm for dimensions 25-50 mm. Precision tolerance of ±0.15 mm is available for profiles under 10 mm with additional die tuning and post-extrusion inspection.

How are the rubber extrusions packed for export?

Standard packing is on wooden spools (1.0 – 1.5 meter diameter) wrapped in stretch film and polyethylene bags, then crated in plywood boxes. For profiles under 10 mm, we also offer coil packing in cardboard cartons. Each spool is labeled with batch number, material grade, and length.

Can I request free samples before placing a bulk order?

Yes. We provide free A4-size sample pieces (300 mm length) of standard compounds for qualification testing. The buyer covers shipping cost. For custom compounds, sample production requires a tooling fee (refundable upon bulk order) and a 10-15 day lead time.

Material	Tensile (MPa)	Compression Set (%)	Max Temp (°C)	Best For
EPDM	8.5 – 11.0	≤ 25	150	Outdoor, UV, ozone
Silicone	6.5 – 8.5	≤ 30	230	High heat, food contact
NBR	10.0 – 14.0	≤ 20	120	Oil, fuel, hydraulic fluid
SBR	7.0 – 9.0	≤ 35	100	Cost-sensitive, dry environments

Send your CAD drawing for a 24-hour quote.