In the field of industrial sealing, the correct choice of material is key to determining equipment service life and reliability. When the working environment is filled with high temperatures, oil, and high-speed operation, general-purpose rubbers often fall short. It is under these conditions that Polyacrylate Rubber (ACM) Sealing Rings stand out as indispensable critical components. This article provides an in-depth analysis of the exceptional performance and unique characteristics of ACM seals.
I. Core Positioning: The Expert in Balancing Heat and Oil Resistance
Polyacrylate Rubber (ACM) is a synthetic rubber copolymerized from alkyl acrylate monomers. It is not a “jack-of-all-trades,” but rather an “expert” material that performs exceptionally well in resisting hot oil and high temperatures. Its market positioning is very clear: to fill the gap where general-purpose Nitrile Rubber (NBR) is inadequate, and the more expensive Fluoroelastomer (FKM) is an overkill, achieving the best balance between performance and cost.
II. Detailed Core Performance and Characteristics
1. Excellent Heat Resistance
- Continuous Operating Temperature: ACM seals can maintain elasticity and sealing performance over the long term in high-temperature environments ranging from 150°C to 175°C, with short-term resistance reaching 180°C or higher. This characteristic far exceeds the limit of Nitrile Rubber (NBR, typically up to 120°C).
- Performance: At high temperatures, the decline in its physical properties (such as hardness, tensile strength) is small, effectively resisting hot air aging and preventing seal failure caused by hardening and cracking.
2. Outstanding Oil Resistance
- Targeted Advantage: ACM has excellent resistance to polar lubricants, gear oils, engine oils, and oils containing sulfur-based extreme pressure additives. In high-temperature oils, it has a low volume swelling rate, maintaining dimensional stability for a long time, which is one of its core advantages.
- Comparative Advantage: In terms of resistance to hot oils, its performance is significantly better than that of NBR and close to that of Fluoroelastomer (FKM), but at a lower cost.
3. Good Ozone and Weather Resistance
ACM seals have strong resistance to ozone aging and good UV resistance. This means they are not only suitable for enclosed oil chambers but can also operate stably in environments partially exposed to air, such as engine compartments, without surface cracking.
4. Good Compression Set Resistance (After Optimization)
The compression set resistance (the ability of a seal to return to its original shape after compression) was a weakness of early ACM products, which could lead to a loss of sealing force. However, through continuous improvements in formulation and process (especially through optimization of the curing system), modern high-performance ACM seals (e.g., epoxy-type ACM) have significantly improved compression set performance, providing lasting and stable sealing pressure.
III. Limitations: An Objective Look at its Shortcomings
No material is perfect. Understanding the limitations of ACM seals is crucial for correct selection.
- Poor Low-Temperature Resistance: This is the main drawback. Its glass transition temperature is relatively high (approximately -15°C to -40°C, depending on the grade), causing it to harden and lose elasticity at low temperatures. Therefore, it is not suitable for applications requiring dynamic sealing at low temperatures.
- Average Water/Steam Resistance: ACM performance degrades rapidly in hot water or steam environments due to hydrolysis, leading to material degradation. It is unsuitable for sealing water, glycol-water fluids, etc.
- Limited Resistance to Acids, Alkalis, and Polar Solvents: Poor resistance to strong polar solvents like ketones, esters, chlorinated hydrocarbons, as well as strong acids and alkalis.
- Moderate Mechanical Strength and Abrasion Resistance: Its tensile strength and abrasion resistance are generally lower than those of natural rubber or polyurethane rubber, requiring careful evaluation in scenarios with severe friction or high pure mechanical loads.
IV. Typical Applications
Leveraging its core advantages, ACM seals are widely used in the following fields:
- Automotive Industry: This is the largest application market. Widely used in automobile engines, transmissions, crankshaft front/rear seals, valve stem seals, power steering systems—any core component in contact with high-temperature lubricating oil.
- Hydraulic Systems: For sealing high-temperature hydraulic oil, such as in heavy machinery, injection molding machines.
- Other Industries: Suitable for various rotary or reciprocating sealing applications requiring heat-resistant oil, such as compressors, reducers.
V. Selection Comparison: Brief Comparison of ACM, NBR, FKM
| Property | Nitrile Rubber (NBR) | Polyacrylate Rubber (ACM) | Fluoroelastomer (FKM) |
|---|---|---|---|
| Heat Resistance | ★★☆ (approx. 120°C) | ★★★☆ (150-175°C) | ★★★★ (200-230°C) |
| Oil Resistance | ★★★ (Good) | ★★★☆ (Excellent, esp. with additives) | ★★★★ (Outstanding) |
| Low-Temp Resistance | ★★★ (down to -40°C) | ★☆ (Poor, > -15°C) | ★★ (down to -20°C) |
| Cost | Low | Medium | High |
| Core Positioning | General-Purpose Oil-Resistant Rubber | Expert in High-Temp Oil Resistance, Cost-Effective | Top-tier Heat/Chemical Resistance |
Conclusion: When to choose ACM?
Polyacrylate Rubber (ACM) seals are the ideal choice when your application meets the following criteria:
- The primary medium is high-temperature lubricating/gear oil.
- The operating temperature is consistently around 150°C, exceeding the limit of NBR.
- Cost-sensitive, where using FKM would be over-specification.
Post time: Nov-20-2025