1. Overview of EPDM

EPDM is a synthetic rubber made by copolymerization of ethylene, propylene and a small amount of diene (such as diene or triene). The material is widely used in many industries, such as automobiles, construction, electronics, refrigeration, etc., due to its excellent performance.

1.1 Chemical composition

The basic structure of EPDM consists of monomers of ethylene and propylene, and its molecular chain contains unsaturated diene. This structure gives EPDM good heat resistance and elasticity, and has certain chemical reactivity.

1.2 Manufacturing process

The production process of EPDM mainly includes the following steps:

• Polymerization: Under high temperature and high pressure, ethylene and propylene undergo polymerization reaction under the action of catalyst to produce polymers.

• Copolymerization: Add an appropriate amount of diene to increase the crosslinking density of the rubber, thereby improving the physical properties.

• Vulcanization: The rubber is crosslinked through the vulcanization process to enhance its strength and elasticity.

2. Performance characteristics of EPDM rubber seals

2.1 Excellent weather resistance

EPDM seals perform well in harsh environments and can resist sunlight ultraviolet rays, ozone and extreme climates. This makes EPDM seals very suitable for outdoor applications, such as window seals in buildings, automotive exterior parts, etc.

2.2 Mechanical properties

• Tensile strength: usually between 15-25 MPa, with good tensile resistance.

• Elongation at break: can be as high as 300-600%, and can maintain good performance even under large deformation conditions.

• Hardness range: EPDM's hardness is usually between 40 and 90 Shore A, suitable for a variety of sealing applications.

2.3 Temperature resistance

EPDM has excellent heat resistance and can maintain stable performance in the range of -40°C to 120°C. The short-term temperature resistance can reach 150°C, which is suitable for various extreme working conditions.

2.4 Chemical resistance

EPDM is highly resistant to chemicals such as water, acid, alkali, and salt, but is less resistant to certain solvents such as oils and alcohols. Therefore, when selecting sealing materials, its chemical compatibility must be considered comprehensively.

3. Analysis of the causes of deformation of the seal ring

3.1 Physical factors

• Over-compression: During installation, if the seal ring is subjected to compression exceeding its elastic limit, it will cause permanent deformation and affect the sealing effect.

• Chemical corrosion: Contact with incompatible chemicals (such as oil, acid, or alkali) will cause the material to swell, harden, or soften.

• Mechanical wear: Frequent mechanical movement and friction can cause damage and deformation to the surface of the seal ring.

3.2 Environmental factors

• Temperature fluctuations: Extreme temperatures can soften or harden EPDM materials, resulting in deformation.

• Aging and UV exposure: Long-term exposure to sunlight or the aging process can cause rubber to harden, crack, and deform.

4. Repair method of EPDM rubber seal ring

4.1 Heat treatment recovery:

Principle of the method: EPDM rubber can recover a certain elastic deformation when heated. This is because the molecular chains of the rubber material will rearrange when heated, and may partially recover its original shape.

Operation steps:

• 1. Heating: Place the seal ring in hot water to heat it, and the water temperature should usually be kept between 70-80 degrees Celsius. Or use a hot air gun to heat the seal ring to 70°C to 80°C. The heating time can be adjusted according to the degree of deformation, generally 5-10 minutes.

• 2. Cooling: After heating, take out the seal ring and place it at room temperature to cool it, allowing it to slowly recover to a shape close to its original shape.

• 3. Repeated treatment: For more severe deformation, it may be necessary to repeat the above heating and cooling process several times.

• Note: Avoid excessive temperatures (over 80°C) to prevent aging or further damage to the rubber.

4.2  Physical correction method:

Principle of the method: Correct the deformation of the rubber seal ring by applying appropriate external force.

Operation steps:

• 1. Use a mold or fixture: Place the seal ring in the prototype mold or clamp it with a suitable fixture.

• 2. Apply uniform pressure: Gently apply uniform pressure to help the seal ring reshape. It is usually necessary to combine with heating to improve the effect.

• Note: Make sure the pressure applied is uniform to avoid damaging the rubber material.

4.3  Soaking softening method:

Method principle: Use an appropriate rubber softener or soapy water to restore the softness of the rubber.

Operation steps:

• 1. Soaking: Soak the seal ring in warm soapy water for 15-30 minutes to help soften the rubber material.

• 2. Gently massage: Gently massage the surface of the seal ring to help it restore its softness.

• Note: Avoid using incompatible solvents or chemicals, as this may cause further damage or degradation of the rubber material.

4.4  Light recovery method:

Method principle: For some EPDM seals that are hardened by ultraviolet rays, appropriately reducing ultraviolet exposure can partially restore their softness.

Operation steps:

• 1. Place in a cool place: Place the seal away from direct sunlight and let it recover naturally in the shade.

• 2. Apply protective agent: Use rubber protective agent (such as silicone-based protective agent) to apply on the surface of the seal to extend its service life and prevent further hardening.

• Note: The light recovery method is slow and usually takes a long time to take effect.

4.5  Chemical repair

There are many rubber repair agents on the market that can effectively fill cracks or gaps on the surface of the seal.

• Repair agent selection: Make sure that the selected repair agent is compatible with EPDM materials.

• Operation method: Apply according to the product instructions to ensure that the repair agent is evenly covered, and finally perform appropriate curing.

6. How to prevent deformation of EPDM rubber seals

1. Correct installation and use: When installing the seal, be sure to follow the manufacturer's instructions to avoid excessive compression. Ensure that the seal is well aligned during installation to reduce stress concentration.

2. Regular maintenance and inspection: Regularly check the status of the seal and replace aging or damaged seals in time.

3. Avoid contact with incompatible chemicals: Try to avoid contact with chemicals that are incompatible with rubber materials, such as mineral oil, strong acid, strong alkali, etc.

4. Control ambient temperature and humidity: Avoid long-term use of the seal in extremely high or low temperature environments to extend its service life.

5. Prevent UV exposure: Try to avoid long-term exposure of the seal to sunlight, use a sunshade or apply a UV protectant when necessary.

Summary

EPDM rubber seals are widely used in various industries due to their superior physical and chemical properties. Understanding the causes of deformation and repair methods can effectively extend their service life and improve the overall performance of the product. However, this recovery is usually limited, and the effect depends on the degree of deformation. Through proper maintenance and regular inspections, deformation can be prevented to a large extent, ensuring the stability and reliability of the seal in various environments.