CR (chloroprene, commonly called Neoprene) and EPDM are both go-to elastomers for weather, water, and outdoor sealing. They look interchangeable on a datasheet, but they are not drop-in substitutes. The wrong choice shows up as premature compression set in hot glycol, brittle cracking under UV, or seal blow-out in a refrigerant line.
Quick answer: Choose EPDM O-rings for continuous hot water, steam, glycol-based fluids, and aggressive outdoor weathering. Choose CR O-rings for refrigerant service, moderate oil exposure, marine environments, and outdoor seals where oil mist or refrigerant contact is possible. If the seal must tolerate petroleum oil, EPDM will fail; if the seal must tolerate glycol brake fluid or saturated steam, CR will fail.
Quick Reference: CR vs EPDM
| Property | CR (Chloroprene / Neoprene) | EPDM |
|---|---|---|
| Ozone & UV weathering | Excellent | Excellent |
| Water resistance (ambient) | Excellent | Excellent |
| Hot water (+80–120°C) | Good | Excellent |
| Saturated steam | Limited — not recommended above +100°C | Excellent (peroxide cure to +150°C) |
| Glycol / coolant | Fair — hardens at high temperature | Excellent |
| Refrigerant compatibility | Excellent | Good to limited |
| Mineral oil / grease | Good | Not suitable (30–80% swell) |
| Brake fluid (glycol DOT 3/4) | Poor | Excellent |
| Temperature range (dry heat) | −35°C to +120°C | −45°C to +150°C (peroxide cure) |
| Low-temperature flexibility | −35°C (standard grade) | −45°C (peroxide cure) |
| Tensile strength | 15–25 MPa | 10–20 MPa |
| Compression set at +100°C | 20–35% | 18–28% (peroxide cure) |
| Relative cost | 1× | 1.0–1.2× |
Polymer Structure: Why the Difference Exists
CR (Chloroprene) Chemistry
CR is produced by polymerizing chloroprene (2-chloro-1,3-butadiene). The repeat unit contains a chlorine atom (~40% by weight) attached to the polymer backbone and retains a small number of C=C double bonds. The chlorine substituent gives CR moderate resistance to non-polar hydrocarbons such as mineral oil and grease, while the stabilized double bonds make CR far more ozone-resistant than NBR, though not as fully saturated as EPDM.
EPDM Chemistry
EPDM is a terpolymer of ethylene, propylene, and a diene termonomer. The main chain is fully saturated — the diene provides side-chain crosslink sites, not backbone double bonds. This makes EPDM inherently ozone- and UV-resistant, resistant to hydrolysis by hot water and steam, and incompatible with petroleum oil. The chlorine atom in CR makes CR more polar: CR tolerates oil and refrigerants better, while EPDM tolerates glycol, steam, and polar solvents better.
Chemistry Comparison Table
| Property | CR | EPDM |
|---|---|---|
| Backbone | Mostly saturated with some residual C=C | Fully saturated C–C backbone |
| Halogen content | Chlorine (~40%) | None |
| Polarity | Moderately polar | Non-polar |
| Oil resistance mechanism | Polar chlorine resists non-polar hydrocarbon absorption | Non-polar backbone absorbs petroleum — swells |
| Ozone resistance | Excellent | Excellent |
| Water/steam resistance | Good to hot water; poor in saturated steam | Excellent |
| Refrigerant compatibility | Excellent (R-134a, R-410A, ammonia) | Good to limited depending on refrigerant |
Temperature Range
| Property | CR (Standard 70 ShA) | EPDM (Peroxide, 70 ShA) | Test Method |
|---|---|---|---|
| Continuous service max (dry heat) | +120°C | +150°C | ASTM D573 |
| Continuous service max (water) | +100°C | +150°C | — |
| Continuous service max (steam) | Not recommended above +100°C | +150°C | — |
| Low-temperature limit (dynamic) | −35°C | −45°C | ASTM D1329 (TR10) |
| Low-temperature limit (static, special grade) | −50°C (G-type) | −55°C | — |
| Compression set, +100°C / 22h | 20–35% | 18–28% | ASTM D395 Method B |
| Compression set, +120°C / 22h | 40–60% | 20–30% | ASTM D395 Method B |
CR has slightly better dynamic toughness than many EPDM grades, but it cannot match EPDM for continuous hot-water or steam service above +100°C. Special low-temperature CR grades (G-type) extend flexibility to approximately −50°C for cold-climate equipment with oil or refrigerant contact.
Ozone & UV Weathering
Both CR and EPDM are excellent choices for outdoor weathering, but for slightly different reasons.
Under ASTM D1171 ozone testing, quality CR compounds show no cracking at 50 pphm / 72 hours, while EPDM routinely passes at 200 pphm. CR's chlorine atom stabilizes residual double bonds; EPDM's saturated backbone has essentially nothing for ozone to cleave.
Practical Outdoor Comparison
| Environmental Factor | CR | EPDM |
|---|---|---|
| Atmospheric ozone (0.02–0.10 ppm) | Excellent — years of service | Excellent — decades of service |
| UV exposure | Good — slight surface oxidation over time | Excellent — minimal surface change |
| Salt spray / marine | Excellent — chlorine content resists salt | Excellent — stable in seawater |
| Cyclic wet/dry | Good | Excellent |
| Abrasion from wind-blown dust | Slightly better | Good |
EPDM is usually preferred for long-life architectural glazing and roofing gaskets because it hardens less over 10–20 years. CR is preferred for marine deck seals, dock bumpers, and outdoor covers where oil or fuel contact is possible.
Water & Steam Resistance
Both resist cold water indefinitely; the divergence appears above +80°C.
| Condition | CR | EPDM | Recommendation |
|---|---|---|---|
| Cold water (ambient) | Excellent | Excellent | Either |
| Warm water (+60°C) | Excellent | Excellent | Either |
| Hot water (+100°C continuous) | Good | Excellent | EPDM preferred |
| Saturated steam (+120°C) | Not suitable | Excellent (peroxide cure) | EPDM required |
| Saturated steam (+150°C) | Not suitable | Excellent (peroxide cure) | EPDM required |
| Boiler feedwater / condensate | Fair — may harden | Excellent | EPDM preferred |
| Deionized / ultrapure water | Good | Excellent | EPDM preferred |
CR can slowly harden in continuous hot-water service, making it acceptable for intermittent exposure but not for boiler seals, steam valves, or continuous hot-water circulation. Specify peroxide-cured EPDM for those conditions.
Refrigerant Compatibility
This is one of the strongest reasons to select CR over EPDM. Chlorinated and fluorinated refrigerants are aggressive toward many elastomers, and CR has a long history as a refrigerant seal material.
| Refrigerant | CR Rating | EPDM Rating | Notes |
|---|---|---|---|
| R-134a (1,1,1,2-tetrafluoroethane) | Excellent | Fair to good | CR is OEM standard |
| R-410A (50/50 R-32/R-125 blend) | Excellent | Limited | CR preferred |
| R-32 (difluoromethane) | Good | Limited | CR preferred |
| R-404A | Excellent | Fair | CR preferred |
| R-407C | Excellent | Fair | CR preferred |
| R-22 (HCFC) | Excellent | Fair | CR standard |
| Ammonia (R-717) | Excellent | Good | CR preferred; verify compound |
| CO₂ (R-744, transcritical) | Fair — depends on pressure | Good | Special compounds required for both |
Always test the compound with the exact refrigerant–lubricant combination per ASTM D471 or OEM protocols. For automotive air-conditioning systems, see our automotive AC application guide.
Oil, Fuel & Chemical Resistance
| Fluid | CR Rating | EPDM Rating | Notes |
|---|---|---|---|
| Mineral hydraulic oil | Good | Not suitable (30–80% swell) | CR usable for light splash; NBR/HNBR better |
| Petroleum grease | Good | Not suitable | CR preferred over EPDM |
| Diesel / gasoline (low aromatic) | Fair | Not suitable | Neither ideal; FKM for fuel |
| Gasoline (high aromatic) | Poor | Not suitable | Use FKM or FFKM |
| Glycol/water coolant | Fair — hardens at high temp | Excellent | EPDM preferred |
| DOT 3/4/5.1 brake fluid | Poor | Excellent | EPDM required |
| Phosphate ester (Skydrol) | Not suitable | Excellent | EPDM required |
| Ketones (acetone, MEK) | Poor | Excellent | EPDM preferred |
| Alcohols (methanol, ethanol) | Fair | Good | Test compound-specifically |
| Dilute acids | Good | Excellent | EPDM preferred |
| Dilute alkalis | Good | Excellent | EPDM preferred |
| Concentrated acids/oxidizers | Poor | Limited | Use FKM or FFKM |
CR tolerates mineral oil and grease better than EPDM, but it is not an oil-seal material — use NBR or HNBR for continuous oil immersion. CR's advantage is in environments where water, ozone, and occasional oil mist or refrigerant coexist. For detailed compatibility, use our chemical compatibility tool.
Mechanical Properties
| Property | CR (Standard 70 ShA) | EPDM (Peroxide, 70 ShA) | Test Method |
|---|---|---|---|
| Tensile strength | 15–25 MPa | 10–20 MPa | ASTM D412 |
| Elongation at break | 250–450% | 200–350% | ASTM D412 |
| Tear resistance (Die C) | 35–55 kN/m | 20–35 kN/m | ASTM D624 |
| Abrasion resistance | Very good | Good | ASTM D5963 |
| Compression set, +100°C / 22h | 20–35% | 18–28% | ASTM D395 Method B |
| Hardness range available | 40–90 Shore A | 40–90 Shore A | ASTM D2240 |
CR generally has higher tensile strength, tear resistance, and abrasion resistance than standard EPDM, making it attractive for dynamic outdoor seals and marine applications. Peroxide-cured EPDM matches or beats CR in compression set resistance above +100°C.
Cost Comparison
| Item | CR | EPDM | Notes |
|---|---|---|---|
| Standard industrial grade | 1× | 0.9–1.1× | Competitive; EPDM often slightly cheaper at volume |
| Refrigerant-grade CR | 1.1–1.3× | N/A | Formulated for specific refrigerant/lubricant |
| Peroxide-cured EPDM | — | 1.1–1.3× | Required for steam and food service |
| FDA/food-contact grade | Limited availability | 1.2–1.5× | EPDM dominates food/pharma |
| Low-temperature grade | 1.2–1.4× | 1.1–1.3× | G-type CR or low-temp EPDM |
Raw-material cost fluctuates, so CR and EPDM often trade places as the lower-cost option. Standard EPDM is usually marginally less expensive than standard CR; refrigerant-grade CR carries a premium due to compound qualification and lower volume.
Application Selection Matrix
| Application | Recommended Material | Rationale |
|---|---|---|
| Outdoor weatherstrip, no oil contact | EPDM | Lower cost; slightly better UV aging |
| Outdoor weatherstrip, possible oil mist | CR | Oil resistance advantage |
| Marine deck seals / dock bumpers | CR | Abrasion, tear, salt resistance |
| Marine fresh-water plumbing | EPDM | Longer life in continuous water |
| Automotive AC refrigerant lines | CR (refrigerant grade) | OEM standard for R-134a/R-1234yf |
| Commercial HVAC gaskets | EPDM | Glycol compatibility and weathering |
| Chiller / refrigeration systems | CR | Refrigerant and lubricant resistance |
| Steam valves / boiler fittings | EPDM (peroxide cure) | CR not rated for saturated steam |
| Automotive cooling system | EPDM | Glycol/water coolant + ozone |
| Brake system (DOT 3/4/5.1) | EPDM | CR incompatible with glycol brake fluid |
| Potable water fitting (NSF 61) | EPDM (certified compound) | CR generally not certified |
| Food/pharma CIP/SIP | EPDM (peroxide or platinum cure) | CR not suitable for steam SIP |
| General outdoor low-dynamic seal | CR | Better tear/abrasion |
| High-cycle water actuator | EPDM (peroxide cure) | Lower compression set at temperature |
Procurement Checklist
Before ordering, confirm with your supplier:
- Continuous operating temperature — include peak spikes and cold-start minimums.
- Fluid list — all fluids, lubricants, refrigerants, coolants, and cleaners the seal will contact.
- Refrigerant type — for CR, specify exact refrigerant and lubricant.
- Cure system — specify peroxide-cured EPDM for hot water or steam; sulfur-cured EPDM is limited to ~+120°C in steam.
- Regulatory compliance — NSF/ANSI 61, FDA 21 CFR §177.2600, USP Class VI, or refrigerant approvals.
- Compression set — state acceptable ASTM D395 Method B limits at operating temperature.
- Hardness and color — 70 Shore A is standard; blue/red for food-contact detectability.
- Size standard — AS568, metric, JIS B 2401, or custom groove dimensions.
- Lead time — standard sizes often ship in 3–5 days; custom compounds 2–4 weeks.
- Certificates — MTR, batch traceability, RoHS/REACH.
FAQ
Q1: Are CR and Neoprene the same thing?
Yes. CR is the ISO/ASTM designation for chloroprene rubber; "Neoprene" is DuPont's original trade name that has become a generic term for chloroprene elastomer.
Q2: Can I use EPDM for refrigerant service?
EPDM is not the first choice for most refrigerants. It generally swells more than CR in refrigerant lubricants and is less reliable in high-pressure blends such as R-410A and R-32. Specify refrigerant-grade CR or OEM-qualified HNBR. See our automotive AC application guide.
Q3: Why does CR fail in glycol brake fluid?
Glycol-based brake fluids attack CR through extraction and swelling. CR can absorb 15–25% volume in glycol brake fluid, causing softening and groove overflow. EPDM is the OEM-standard material for glycol brake fluid seals.
Q4: Is CR better than EPDM for outdoor use?
Both are excellent outdoors. CR is better when oil mist, fuel, refrigerant, or physical abuse is possible. EPDM is better for continuous hot water, steam, glycol coolants, and very long-term UV exposure.
Q5: Can CR handle steam?
CR is not recommended for saturated steam above +100°C. Residual C=C bonds and chlorine content lead to hardening and cracking. For steam, specify peroxide-cured EPDM (to +150°C) or FFKM/AFLAS above that.
Q6: Which material is more oil-resistant, CR or EPDM?
CR is significantly more oil-resistant than EPDM and tolerates light oil splash and grease. However, CR is not a substitute for NBR or HNBR in continuous oil immersion.
Q7: Does CR cost more than EPDM?
Standard CR and EPDM are typically close in price, with EPDM often slightly cheaper in volume. Refrigerant-grade and low-temperature CR compounds carry a premium.
Q8: What is the lowest temperature each material can handle?
Standard CR is serviceable to approximately −35°C; G-type grades reach about −50°C. Standard EPDM reaches approximately −45°C, with specialized compounds reaching −55°C or lower. Verify the TR10 value on the datasheet.
---
Still deciding between CR and EPDM? Request a quote with your fluid type, operating temperature, refrigerant specification, and any NSF/FDA requirements — we stock both CR and EPDM O-rings in standard AS568 and metric sizes, with refrigerant-grade CR and peroxide-cured EPDM available. For compound-specific questions, contact our engineering team.