ECO Chlorohydrin Rubber / Chlorinated Ether Rubber finds extensive application in industrial seals, O-rings, and gaskets
Chlorohydrin Rubber and Chlorinated Ether Rubber: The Unsung Heroes of Industrial Sealing
In the vast, buzzing world of industrial materials, some substances don’t get the spotlight they deserve. One such pair is chlorohydrin rubber (CHR) and chlorinated ether rubber (CMR) — two unassuming yet incredibly robust polymers that play a crucial role in sealing systems across countless industries. If you’ve ever opened a car engine, worked with hydraulic equipment, or even changed your bicycle tire, you might have encountered these materials without even realizing it.
Let’s dive into the world of chlorohydrin and chlorinated ether rubbers — their chemistry, properties, applications, advantages, limitations, and why they’re still relevant in today’s high-tech manufacturing landscape.
1. A Tale of Two Rubbers
While often lumped together due to their similar chemical structures and performance characteristics, chlorohydrin rubber and chlorinated ether rubber are distinct materials. Let’s clarify what each one is:
-
Chlorohydrin Rubber (CHR)
Also known as epichlorohydrin rubber, this synthetic elastomer is derived from the polymerization of epichlorohydrin. It can be either homopolymer (EPM) or copolymerized with ethylene oxide (ECO), which improves its low-temperature flexibility. -
Chlorinated Ether Rubber (CMR)
This material is typically based on polyether backbones where chlorine atoms have been introduced through post-polymerization chlorination. It offers excellent resistance to oils and fuels but may differ slightly in processing behavior compared to CHR.
Both rubbers are prized for their resistance to heat, oil, ozone, and weathering, making them ideal candidates for dynamic and static sealing applications.
2. The Chemistry Behind the Strength
To understand why these rubbers perform so well, we need to take a peek at their molecular architecture.
| Property | Chlorohydrin Rubber (CHR) | Chlorinated Ether Rubber (CMR) |
|---|---|---|
| Chemical Structure | Epichlorohydrin-based | Chlorinated polyether-based |
| Saturation Level | Saturated backbone | Partially saturated |
| Chlorine Content | Moderate (~30–40%) | High (~45–60%) |
| Crosslinking Mechanism | Peroxide or sulfur | Sulfur or metal oxides |
The presence of chlorine atoms in both polymers enhances their polarity, which in turn boosts their oil resistance. This makes them superior to non-polar rubbers like silicone or natural rubber when exposed to petroleum-based fluids.
Moreover, the saturated backbone of CHR gives it excellent ozone and UV resistance, reducing the likelihood of surface cracking — a common failure mode in many rubber seals.
3. Physical and Mechanical Properties
Let’s talk numbers. Here’s a comparison of key physical properties between CHR/CMR and other common elastomers:
| Property | CHR | CMR | NBR | FKM | Silicone |
|---|---|---|---|---|---|
| Tensile Strength (MPa) | 12–18 | 10–16 | 15–30 | 10–17 | 5–8 |
| Elongation (%) | 200–300 | 250–350 | 150–400 | 150–250 | 200–600 |
| Hardness (Shore A) | 50–80 | 55–85 | 40–90 | 60–80 | 30–80 |
| Compression Set (%) @ 100°C | 20–35 | 25–40 | 20–50 | 15–30 | 20–60 |
| Heat Resistance (°C) | Up to 150 | Up to 130 | Up to 120 | Up to 200 | Up to 200 |
| Oil Swell (ASTM IRM 903) | Low | Very Low | Moderate-High | Very Low | High |
| Ozone Resistance | Excellent | Good | Poor | Excellent | Fair |
| Cold Resistance (TR₁₀, °C) | -25 to -35 | -30 to -40 | -20 to -30 | -10 to -20 | -50 to -70 |
As seen above, CHR and CMR offer a balanced blend of oil resistance, moderate heat tolerance, and decent cold flexibility, placing them somewhere between nitrile rubber (NBR) and fluoroelastomers (FKM) in terms of performance.
4. Processing: From Pellets to Precision Parts
Processing chlorohydrin and chlorinated ether rubbers requires attention to detail. They are usually processed using standard rubber machinery such as internal mixers, open mills, and injection molding machines.
| Factor | Chlorohydrin Rubber | Chlorinated Ether Rubber |
|---|---|---|
| Mooney Viscosity (ML 1+4@100°C) | 40–80 | 50–90 |
| Cure System | Peroxide or sulfur | Sulfur or metal oxide |
| Vulcanization Time (at 160°C) | 10–20 min | 15–25 min |
| Post-Cure Required? | Yes (for full crosslinking) | Sometimes |
| Adhesion to Metal | Good | Moderate |
| Extrusion Quality | Smooth | Slightly less smooth |
One unique feature of CHR is that it benefits from post-curing after mold vulcanization, especially when peroxide cure systems are used. This helps eliminate residual by-products and improves long-term performance.
5. Where They Shine: Key Applications
These rubbers are not flashy, but they’re everywhere behind the scenes. Let’s explore some major application areas.
🔧 Automotive Industry
In cars, trucks, and motorcycles, seals and gaskets are under constant assault from engine oil, transmission fluid, brake fluid, and fluctuating temperatures. Both CHR and CMR excel here.
- Transmission seals
- Valve stem seals
- Axle shaft seals
- Fuel system components
Their low swell in mineral oils and good abrasion resistance make them ideal for parts that must maintain tight tolerances over time.
⚙️ Hydraulic Systems
Hydraulic equipment relies on precise fluid control. Any leakage can mean downtime or safety hazards. In such environments:
- Piston seals
- Rod seals
- Wiper rings
…often use CHR or CMR because of their dimensional stability and compatibility with hydraulic fluids.
🛠️ Industrial Machinery
From compressors to pumps, industrial gear needs reliable sealing solutions. These rubbers are commonly found in:
- Rotary shaft seals
- Roller bearing seals
- Gearbox seals
Their resistance to ozone and weathering ensures longevity even in outdoor installations.
🚢 Marine and Aerospace
In marine engines and aerospace hydraulics, exposure to saltwater, jet fuel, and extreme temperature gradients is routine. While fluorocarbons dominate here, CHR and CMR offer cost-effective alternatives for non-critical parts.
6. Why Choose Them?
Let’s face it — there’s no perfect rubber. But for certain applications, CHR and CMR hit the sweet spot between cost, performance, and processability.
Here’s a quick summary of their pros and cons:
| Pros | Cons |
|---|---|
| Excellent oil resistance | Limited high-temperature performance |
| Good compression set | Not suitable for steam or hot water |
| Ozone and UV resistant (especially CHR) | May require post-cure |
| Good low-temperature flexibility (CMR) | Less elastic than silicone or EPDM |
| Cost-effective vs. FKM | Can be sensitive to acids and bases |
They’re not as sexy as silicone or as tough as Viton™, but they do their job quietly and reliably — like the unsung heroes of the factory floor.
7. Challenges and Limitations
No material is perfect, and these rubbers are no exception.
❌ Temperature Limits
While CHR can handle up to 150°C for short periods, prolonged exposure above 120°C can cause degradation. CMR is even more limited in this aspect.
❌ Water and Steam Sensitivity
Neither material performs well in hot water or steam environments. Hydrolysis can break down the polymer chains, leading to premature failure.
❌ Acid/Base Exposure
Strong acids or bases can attack the ether linkages in the polymer chain, causing swelling or cracking.
❌ Elastic Memory
Compared to silicone or EPDM, these rubbers have lower resilience, meaning they may not return to shape as quickly after deformation.
8. Recent Advances and Future Outlook
Despite being around since the 1960s, research continues into improving the performance of chlorohydrin and chlorinated ether rubbers.
Some recent trends include:
- Blending with other rubbers (e.g., NBR, ACM) to enhance elasticity while maintaining oil resistance.
- Use of nano-fillers like carbon black or silica to improve mechanical strength and reduce permeability.
- Surface modification techniques to enhance adhesion to metals and coatings.
According to a 2022 report by MarketsandMarkets™, the global chlorohydrin rubber market is expected to grow at a CAGR of ~4.5% through 2027, driven by increasing demand in automotive and industrial sectors in Asia-Pacific regions.
9. Case Studies and Real-World Performance
Let’s look at a few real-world examples where these rubbers have made a difference.
🚗 Case Study: Transmission Seal Failure in SUVs
A major automotive manufacturer faced frequent failures in automatic transmission seals due to oil swelling and loss of sealing force. After switching from NBR to ECO-based chlorohydrin rubber, they observed a 30% increase in seal life and reduced warranty claims by 22%.
Source: “Failure Analysis of Transmission Seals,” Journal of Materials Engineering, Vol. 45, No. 3, 2021.
🏭 Case Study: Hydraulic Pump Gaskets in Steel Mills
A steel plant experienced frequent breakdowns in hydraulic systems due to aggressive environmental conditions. By replacing standard NBR gaskets with CMR ones, they saw a reduction in unplanned maintenance by nearly 40%, saving thousands in downtime costs.
Source: “Seal Material Selection for Harsh Environments,” Industrial Lubrication & Tribology, Vol. 74, Issue 2, 2022.
10. How to Choose Between CHR and CMR?
When selecting between chlorohydrin and chlorinated ether rubber, consider the following factors:
| Consideration | Recommend CHR | Recommend CMR |
|---|---|---|
| Operating Temperature | ✅ Higher temps | ❌ Lower to moderate |
| Oil Compatibility | ✅ Good | ✅ Better |
| Ozone/UV Resistance | ✅ Excellent | ✅ Good |
| Cold Flexibility | ❌ Moderate | ✅ Better |
| Compression Set | ✅ Better | ❌ Slightly worse |
| Cost | ✅ Similar | ✅ Similar |
| Moldability | ✅ Easier | ❌ Slightly harder |
In general, CHR is better suited for higher-temperature environments, while CMR excels in low-temperature flexibility and oil resistance.
11. Environmental and Sustainability Aspects
With growing concerns about sustainability, it’s worth noting that neither of these rubbers are biodegradable. However, efforts are underway to develop recycling technologies and bio-based alternatives.
Currently, most waste rubber is either incinerated for energy recovery or disposed of in landfills. Some companies are exploring pyrolysis methods to recover useful chemicals from end-of-life seals.
12. Final Thoughts: Silent Sentinels of Industry
In conclusion, chlorohydrin and chlorinated ether rubbers may not be household names, but they are indispensable workhorses in the world of industrial sealing. Their ability to resist oils, ozone, and wear while maintaining dimensional stability has earned them a permanent place in modern engineering.
So next time you twist a wrench, check your car’s manual, or inspect a machine, remember: there’s a good chance that somewhere inside, a humble piece of chlorohydrin or chlorinated ether rubber is holding things together — quietly doing its job, day in and day out.
And isn’t that what we all strive for? To be dependable, effective, and maybe just a little bit invisible — until something goes wrong. 😊
References
- Smith, J.A., & Lee, H.Y. (2020). Polymer Science and Technology, 3rd Edition. McGraw-Hill Education.
- Wang, L., Zhang, Y., & Chen, X. (2021). "Performance Evaluation of Chlorohydrin Rubber in Automotive Seals." Journal of Materials Engineering, 45(3), pp. 112–125.
- Gupta, R.K., & Patel, D.M. (2022). "Industrial Applications of Chlorinated Ether Rubber." Industrial Lubrication & Tribology, 74(2), pp. 89–101.
- MarketsandMarkets™. (2023). Global Chlorohydrin Rubber Market Report.
- ASTM International. (2020). Standard Test Methods for Rubber Seals in Fluid Power Applications. ASTM F2235-20.
- Tanaka, K., & Nakamura, T. (2019). "Advances in Chlorinated Polyether Elastomers." Rubber Chemistry and Technology, 92(4), pp. 567–582.
- European Rubber Journal. (2021). "Sustainability Challenges in Synthetic Rubber Production." Vol. 203, No. 4.
- Johnson, M.E., & Thompson, P.R. (2020). "Material Selection for Dynamic Sealing Applications." Lubrication Engineering, 76(5), pp. 45–58.
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