Rubber & Silicone Material Selection Guide

Rubber and Silicone Material Selection Guide

Anlintech supplies custom molded rubber and silicone parts and helps engineers choose the right elastomer before tooling begins. The six families below cover most sealing and gasket work: FKM/Viton resists heat, fuel and aggressive chemicals up to 200 C; silicone stays flexible from -60 C to 200 C and meets FDA and USP Class VI for food and medical contact; NBR is the cost-effective choice for oil and fuel up to 100 C; EPDM resists weather, ozone, steam and hot water; HNBR adds heat and oil resistance for automotive powertrain; FFKM approaches PTFE chemical resistance while remaining elastomeric. Start with the comparison table, then send a drawing with material, hardness and quantity to receive a quote within two business days.

FKM / Viton

FKM, commonly known as Viton, is a fluorocarbon rubber rated for continuous service from -20 C to 200 C with short peaks near 230 C. It resists gasoline, diesel, hydraulic fluid, acids and most solvents, which is why it is specified for fuel-system seals, engine gaskets and chemical-pump components. FKM is not suitable for brake fluid, amines or hot steam, and its low-temperature flexibility is poorer than silicone.

Silicone

Silicone rubber stays elastic from -60 C to 200 C and is inherently clean, odorless and tasteless. Anlintech supplies FDA-compliant and USP Class VI silicone for food, beverage, medical and infant-contact parts. Silicone has lower tensile strength than FKM or NBR, so it is chosen for temperature range and biocompatibility rather than high mechanical load or abrasion.

NBR

Nitrile, or NBR, is a copolymer of acrylonitrile and butadiene with good resistance to petroleum oils, fuels and greases at temperatures from -40 C to 100 C. It is the standard low-cost material for O-rings, oil seals and fuel-handling gaskets. NBR performs poorly outdoors because ozone and weather crack it over time, so it is not used for exterior weatherstripping.

EPDM

EPDM is an ethylene-propylene rubber that resists weather, ozone, UV, steam and hot water up to 150 C. It is widely used for outdoor seals, HVAC gaskets, automotive weatherstrips and radiator hoses. EPDM is not compatible with petroleum oils or fuels and should never be specified where oil contact is expected.

HNBR

Hydrogenated NBR, or HNBR, is NBR with a saturated backbone, raising the service ceiling to 150 C and improving oil, ozone and abrasion resistance. It is the default elastomer for automotive timing belts, power-steering seals and downhole oil-and-gas equipment. HNBR costs more than NBR but lasts far longer under heat and pressure.

FFKM

Perfluoroelastomer, or FFKM, places fluorine on every backbone chain and resists nearly all chemicals across -20 C to 320 C. It is used where FKM fails: semiconductor, aggressive-acid and high-purity pharmaceutical service. FFKM is the most expensive family and is specified only when no other elastomer survives the media.

Molding processes

Anlintech molds parts by four processes. Compression molding suits large or simple shapes and low volumes from 100 to 10,000 pieces. Transfer molding gives better flash control for medium runs. Injection molding is the choice for high volume, tight tolerances and complex geometries from 10,000 to millions of pieces, with cycle times of 30 to 120 seconds. Liquid silicone rubber injection is used for silicone parts requiring flash-free, high-precision medical and food components. Prototype tooling is cut in 7 to 15 days and production tooling in 2 to 4 weeks.

Size standards and tolerances

Anlintech machines to the major global O-ring and gasket standards so parts interchange with catalog items. AS568 covers US dash numbers and cross-sections, ISO 3601 covers metric sizes, JIS B2401 covers Japanese sizes and GB/T 3452 serves the Chinese market. Standard O-ring cross-sections run from 1.02 mm to 6.99 mm with custom cross-sections available. Dimensional tolerance for molded parts is typically plus or minus 0.1 mm on small features and plus or minus 0.3 mm on diameters above 50 mm.

Hardness and durometer guidance

Elastomer hardness is measured on the Shore A scale, where 40 is soft and 90 is rigid. Soft parts at 40 to 60 Shore A seal better against rough surfaces and low pressure, while hard parts at 70 to 90 Shore A resist extrusion, compression set and high pressure. Most static seals use 70 Shore A, dynamic seals use 60 to 75 Shore A and LSR medical parts range from 30 to 80 Shore A. Anlintech measures every batch on a durometer and reports the value on the inspection certificate.

Chemical compatibility quick reference

For petroleum oil and diesel, choose NBR, HNBR or FKM. For gasoline and biodiesel, choose FKM or HNBR. For steam, hot water and brake fluid, choose EPDM and avoid FKM. For strong acids and solvents in semiconductor or pharma lines, choose FFKM. For food, beverage and medical contact, choose FDA or USP Class VI silicone. When the media is unknown, send the fluid name and concentration to Anlintech for a compatibility check before tooling.

How to specify your custom part

Send the following to receive an accurate quote:

1. a 2D drawing or 3D STEP file with all critical dimensions;
2. the elastomer and hardness in Shore A;
3. the service media, temperature and pressure;
4. required quantity and annual volume;
5. the applicable standard such as AS568, ISO 3601 or JIS B2401;
6. any certification needs including FDA, USP Class VI, RoHS or REACH.

Anlintech returns a quote, tooling plan and lead time, usually within two business days.

Industries served

Anlintech supplies across four main sectors. Automotive programs use NBR, HNBR and FKM for seals, grommets and vibration parts on engines and transmissions. Oil and gas relies on FKM and FFKM for downhole and surface seals rated to 200 C and high pressure. Semiconductor fabs specify FFKM and high-purity silicone for wet-bench and vacuum components where contamination must stay below 1 ppb. Medical and food customers receive FDA and USP Class VI silicone for tubing, stoppers and valves. Across all sectors Anlintech holds ISO 9001:2015 and ships with full material traceability and inspection reports.

Quality, traceability and certifications

Every Anlintech batch ships with a material certificate, a factory inspection report and full lot traceability from raw compound to finished part. The Dongguan plant is ISO 9001:2015 certified and runs incoming, in-process and final inspection. Available compliance includes FDA, USP Class VI, RoHS and REACH on request, and first-article inspection reports are provided for production programs.

Common failure modes and how to avoid them

The most frequent seal failure is compression set, where a part stays permanently deformed after long heat exposure. Choose a higher-grade elastomer such as FKM or HNBR and keep the application below the rated temperature to avoid it. Extrusion happens when a soft seal is pushed into a gap under high pressure, so raise hardness to 80 to 90 Shore A or add a backup ring. Chemical swelling occurs when the elastomer absorbs the media and grows, which is why a compatibility check must run against the actual fluid and its additives, not just the elastomer family name. Finally, assembly damage from sharp tools or twisted installation causes leaks that look like material failure, so use installation sleeves and a compatible grease. Reviewing these four modes during design prevents most field returns.

From inquiry to production

A typical Anlintech project runs in five steps. First, the customer sends a drawing or sample and the service conditions. Second, Anlintech recommends material and hardness and returns a quote within two business days. Third, prototype tooling is cut in 7 to 15 days and samples are shipped for approval. Fourth, production tooling is built in 2 to 4 weeks once the prototype passes. Fifth, volume production runs from 100 pieces to millions per the agreed schedule, with inspection reports on every lot. This predictable path is why buyers in automotive, oil and gas, semiconductor and medical reuse Anlintech across programs.

Global delivery and lead times

Anlintech ships worldwide from Dongguan, Guangdong, China and serves customers in more than 30 countries across North America, Europe and Asia. Samples are dispatched by express within 24 hours of approval, and production orders ship by air or sea depending on volume and urgency. Typical transit is 3 to 7 days by air and 20 to 35 days by sea to the United States. Anlintech prepares export documentation, material declarations and REACH or RoHS files so buyers clear customs without delay. This logistics support is a key reason US distributors and OEMs keep Anlintech as a repeat supplier.

Rubber part design fundamentals

A well-designed rubber component starts with the function it must perform, not with the material alone. Engineers should first define the fluid or gas the part will contact, the temperature the part will see during operation and at rest, the pressure it must hold, and the motion it must allow or block. With those four facts known, the elastomer choice becomes a short list rather than a guess. Anlintech reviews the operating envelope with the customer and proposes two or three candidate materials with their tradeoffs, so the final selection is justified by data instead of habit. This collaborative method reduces late changes and protects the production schedule.

Geometry matters as much as chemistry. Sharp corners, thin walls and deep undercuts raise scrap rates and weaken the part at the exact spot that carries load. A small fillet, a slightly thicker section or a relocated parting line often removes the risk without changing the function. Anlintech flags these issues during design review and suggests fixes that keep the drawing close to the original intent while making the part moldable and durable.

Why work with a dedicated rubber molder

Choosing a supplier that molds rubber every day changes the outcome of a project. A dedicated molder catches tolerance risks before tooling is cut, recommends a cheaper process when volume allows, and warns about a material that will fail in the real media. Anlintech brings that discipline to every program, from a single prototype cavity to high-volume production. The result is fewer surprises, shorter lead times, and parts that pass inspection the first time. For buyers managing several product families across regions, a single accountable molder also simplifies audits, documentation and traceability.