1. Selection Conclusions First

This chart can be used as core content on the first screen of the page. Users are usually not searching to "learn material chemistry," but to judge: is the raw material selected correctly, and is there a more suitable substitute material?

2. ACM: The "Automotive Sealing-Type" Material Among High-Temperature Oil Products

ACM, acrylate rubber, is suitable for scenarios described as "high-temperature oil, engine oil, transmission fluid, media containing sulfur or additive lubricants."

Its main value is not "being more high-grade than FKM," but performing better in certain automotive oil environments against heat aging, oxidation aging, ozone. Parker's material description explains ACM as having good resistance to mineral oil, oxygen and ozone, but water compatibility and low-temperature performance are inferior to NBR; Trelleborg also points out ACM is mainly used for automotive applications requiring high-temperature oil with additives.

When to Consider ACM?

Typical situations suited to using ACM:

Misconceptions About ACM

ACM is not a "universal oil-resistant material." It is more like a high-temperature oil dedicated material. If the problem comes from fuel, aromatics, strong solvents, hot water, steam or low-temperature embrittlement, ACM may not be the correct answer.

Substitution Relationships for ACM

3. AEM: A Better Upgrade Option for Low-Temperature and Complex Automotive Oil Products Than ACM

AEM, ethylene acrylate rubber, common commodity names include Vamac.

It has significant overlap with ACM's application area, but AEM is more placed under discussion in automotive engine, transmission, oil-gas mixed, thermal ventilation and combustion oil-cooling environments. Parker describes AEM as a mixed polymer material of ethylene, methyl acrylate and cure-site monomers, and points out it can be seen as a broader-performance polyacrylate ester material; DuPont's Vamac data also clearly places AEM in needing heat resistance, engine oil, transmission oil and blow-by gas automotive applications.

When to Switch to AEM?

What Is AEM Not Suitable For?

AEM is not FKM, nor is it FEPM. It should not be promoted as a "broadly universal chemical material." If the medium is strong acid, strong alkali, amines, ketones, esters, hot water steam or complex chemical media, AEM needs careful validation.

Substitution Relationships for AEM

4. FEPM/AFLAS: A More Valuable Choice When Ordinary FKM Meets Acid, Alkali, Hot Water or Special Chemicals

FEPM is tetrafluoroethylene-propylene copolymer elastomer, and AFLAS is one of its common commodity names.

This is one of the most valuable pieces of content on the page, because many users mistakenly believe "FKM/Viton is the most chemically resistant O-ring." This is not entirely correct. Ordinary FKM can fail in certain amines, strong alkali, hot water, steam, some cooling liquid additives or heat and refrigeration oil-based chemicals or special additives, and FEPM/AFLAS is precisely the substitute for filling these boundary scenarios.

Parker describes FEPM/AFLAS as a copolymer of TFE and propylene, and emphasizes its excellent resistance against broad corrosive media; AGC's data on AFLAS also characterizes it as heat resistant, acid resistant, alkali/amine and hot steam resistant, and points out it outperforms ordinary FKM in strong alkalinity.

When Is FEPM/AFLAS Needed?

AGC's application data also lists semiconductor sealing, steam, oilfield, mechanical seal, marine engine coolant and transmission sealing directions for AFLAS applications, which belong to scenarios "outside ordinary material boundaries."

Relationship Between FEPM/AFLAS and FKM

FEPM/AFLAS Substitute Materials

Wording to avoid: don't write FEPM/AFLAS as "comprehensively better than FKM." A more accurate expression is:

FEPM/AFLAS is an important substitute material when ordinary FKM is not suitable for amines, alkali, hot water, steam or special additives.

5. CR: A Balanced Material of Moderate Cold Resistance, Ozone Resistance, and Moderate Oil Resistance

CR, chloroprene rubber, also commonly called Neoprene.

CR's value is in balance: it is not the most oil resistant, nor the most heat resistant, nor even the most chemically resistant; but it has relatively balanced performance among cold resistance, ozone resistance, aging resistance, and a certain degree of oil resistance. Parker notes CR has good ozone, aging and chemical acceptance, and maintains good mechanical properties across a relatively wide temperature range; Trelleborg also categorizes CR's advantages as ozone resistance, weathering resistance, chemical resistance, aging resistance and good mechanical properties.

When to Consider CR?

How Should CR Not Be Used?

CR is not suitable to be treated as a high-end oil-resistant material, nor should it substitute for FKM in high-temperature, fuel, strong solvent or strongly corrosive chemical media.

Substitution Relationships for CR

6. AU/EU Polyurethane: Not for Chemical Resistance, but for Abrasion and High Mechanical Strength

AU/EU belong to polyurethane rubber, AU usually refers to polyester-type polyurethane, EU usually refers to polyether-type polyurethane.

The key words of polyurethane O-rings are not "chemical resistant" or "high temperature resistant," but:

Wear resistance, anti-tearing, high tensile strength, anti-extrusion, dynamic sealing lifespan.

Trelleborg summarizes polyurethane's features as excellent elasticity, best abrasion resistance, outstanding tensile strength, low compression set and good oxygen/ozone resistance; ERIKS also points out PUR and special XNBR can provide the best abrasion performance.

When Is AU/EU Needed?

Differences Between AU and EU

COG's polyether-type polyurethane materials also explicitly point out EU O-rings have better hydrolysis resistance than AU materials, and are more durable in water-based media.

Misconceptions About AU/EU

Polyurethane O-rings are most easily misused in the following scenarios:

The polyurethane page should reiterate one point: if the failure cause is abrasion, tearing, extrusion, AU/EU is meaningful; if the failure cause is chemical corrosion, priority should go to media compatibility.

7. ECO: An Epichlorohydrin Rubber Balanced Material, Commonly Used for Automotive Fuel, Oil-Gas Intake, Soft Tube, Diaphragm, Sealing Components

ECO, epichlorohydrin rubber, commonly used in automotive fuel, oil-gas intake, soft tube, air conditioning and vibration reduction areas.

It can be understood as: a balanced solution providing fuel/oil-resistant, low permeation, ozone-resistant, low-temperature performance between NBR, CR, FKM. Zeon's Hydrin ECO data describes it as a balanced material with heat, oil, fuel, low permeation, ozone resistance and low-temperature flexibility, and lists automotive fuel hose, intake system, tube, air conditioning and vibration reduction applications; Osaka Soda also points out epichlorohydrin rubber has oil resistance, low temperature, ozone and fuel/gas barrier related characteristics.

When to Consider ECO?

Relationship Between ECO and NBR, FKM

ECO should not be written as "a low-cost substitute for FKM." The more accurate statement is:

ECO is suitable for scenarios requiring fuel, oil-gas, low permeation and ozone resistance balance, but does not necessarily need FKM's comprehensive chemical resistance capability.

8. Constructed by "Special Media," Not by Material Names

This kind of page has the greatest content structure value when built around "special media" and "failure mode," not the material alphabet.

8.1 High-Temperature Oil, Engine Oil, Transmission Oil

Priority consider:

HNBR: More heat resistant, more oil resistant, more mechanical aging resistant than NBR.

ACM: High-temperature oil products, automotive oil seal, transmission oil environment.

AEM: High-temperature oil products, and needing better low-temperature and comprehensive automotive performance.

FKM: More high-temperature, wider chemically compatible.

ERIKS' sealing material manual also emphasizes that additives in oil products significantly affect rubber compatibility, especially in synthetic oil, hydraulic oil, engine oil and fuel scenarios, one cannot select materials only by "oil resistant" two words.

8.2 Hot Water, Steam, Cooling Liquid

Priority consider:

Note: FKM does not equal "hot water steam priority material." FKM, steam, amines, strong alkali scenarios often need to skip ordinary FKM.

8.3 Amines, Alkali, Acid-Alkali Compound Media

Priority consider:

One must avoid a claim that "a certain material is acid-alkali resistant." Acid, alkali, concentration, temperature, duration and cleaning agent systems are entirely different, results may be contrary.

8.4 Fuel, Diesel, Gasoline, Alcohol-Containing Fuel, Oil and Gas

Priority consider:

ERIKS also points out fuel is a complex mixture, and sealing material selection needs to consider differences of aromatics, alcohol type, additives, etc, usually needing testing verification.

8.5 High Wear, High Pressure, Dynamic Seal

Priority consider:

It needs to be emphasized here: many "material failures" are actually structural failures. If groove dimension, compression amount, clearance, surface roughness, lubrication and pressure peak value are not reasonable, replacing with even more expensive material may not solve the problem.

9. Substitute Paths from Special Materials to Common Materials

9.1 Starting from NBR

9.2 Starting from FKM

9.3 Starting from EPDM

9.4 Starting from HNBR

10. Fields That Must Be Confirmed Before Selection

This type of page should ultimately place a "price quote/selection field table," used to convert traffic into effective consultation.

Trelleborg's compatibility explanation also emphasizes that rubber and media's actual performance is affected by temperature, pressure, media composition, mechanical properties and other factors; laboratory compatibility tables cannot fully substitute for actual working condition testing.

11. FAQ Direction

Q1: Which is More Suitable for ACM and AEM for Automotive Oil Products?

Both are usable for automotive oil products and high-temperature environments. Generally, ACM is more suited to high-temperature hot oil applications, AEM emphasizes low temperature and blow-by comprehensive performance in the automotive environment. The specific choice should look at oil product type, temperature, low-temperature startup requirement and seal form.

Q2: Can FEPM/AFLAS Replace FKM?

It can be substituted in certain special media, such as amines, alkali, hot water, steam, media containing additives cooling liquid, but it is not a comprehensive upgrade for all FKM operating conditions. Fuel oil, low temperature, cost and processability still need to be evaluated separately.

Q3: Is AU Polyurethane O-Ring the Most Wear Resistant?

Polyurethane is usually a very outstanding elastomer material for wear resistance and high mechanical strength, suitable for dynamic wear, high tearing and anti-extrusion scenarios. But it is not suitable to be used as a high-temperature steam, strong acid-alkali or broad chemical media material.

Q4: Is CR Still Necessary to Use?

Yes. CR's advantage is the balance of weathering, ozone resistance, mechanical properties and a certain oil resistance. It is suitable for some outdoor, moderate oil, refrigeration or general industrial environments, but should not substitute for FKM, HNBR or FEPM used in high-end chemical or high-temperature oil conditions.

Q5: What Is the Relationship Between ECO and NBR, FKM?

ECO can be seen as an intermediate balanced material between NBR and FKM, especially suitable for scenarios requiring simultaneous fuel, oil-gas, low permeation, ozone resistance and low-temperature performance. But if temperature and chemical corrosion resistance requirements are very high, may need to switch to FKM, FVMQ or FFKM.