How To Improve The Aging Resistance Of Rubber Seals?

The main types of aging of rubber seals

Rubber seal aging refers to the process of deterioration of the performance of rubber materials under the action of environmental factors (such as light, heat, oxygen, ozone, mechanical stress, etc.). The main types of aging include:

Thermal-oxidative aging: Under the combined action of heat and oxygen, the rubber molecular chain undergoes oxidative degradation or cross-linking.

Ozone Aging: Ozone reacts with rubber double bonds, resulting in surface cracks (ozone cracks).

Photoaging: Ultraviolet rays trigger the photooxidative decomposition of rubber molecules, producing free radicals to accelerate aging.

Damp heat aging: In a high-humidity environment, water vapor promotes the hydrolysis of rubber or accelerates oxidation.

Mechanical aging: Dynamic stress and friction cause microcracks to propagate, further accelerating aging.

A method to improve the aging resistance of rubber

Material selection and formulation optimization

Choose the type of rubber seal with excellent aging resistance:

Rubbers with high saturation: such as hydrogenated nitrile butadiene rubber (HNBR), ethylene propylene rubber (EPDM), and fluoroelastomer (FKM), due to the high saturation in the molecular structure, the low double bond content, and better oxidation and ozone resistance.

Silicone rubber (SiR) is excellent at resisting heat, ozone, and UV but relatively weak at maintaining mechanical strength.

Recipe Design Optimization:

Filler: Nano filler (such as nano-silica or nano calcium carbonate) or modified carbon black is selected to improve rubber's strength and aging resistance.

Plasticizers: Choose plasticizers with good stability, such as phthalates (DOA, DOP) or environmentally friendly plasticizers, to avoid aging caused by plasticizer decomposition.

Cross-linking system: Use a peroxide cross-linking system (such as di-tert-butyl peroxide) instead of sulfur cross-linking to avoid the problem of thermal and oxygen degradation of vulcanized rubber.

Add anti-aging agents

The anti-aging agent is an important measure to improve the aging resistance of rubber seals. Commonly used anti-aging agents include:

Antioxidant:

Antioxidants include hydroquinone (BHT) and phosphite, which can capture free radicals and slow down oxidant reactions.

Ultraviolet absorbers, such as benzophenones (UV-531) and parabens, absorb ultraviolet rays and convert them into heat.

Metal passivator: inhibits the reaction of rubber with catalytically oxidized metal ions.

Ozone inhibitors:

Paraffin wax (e.g. microcrystalline paraffin): Prevents ozone exposure by migrating to the rubber surface to form a barrier.

Chemical ozone inhibitors (e.g., diphenylamines, amine antioxidants): react with ozone to reduce ozone concentrations.

Co-stabilizers: Synergistically used with antioxidants and UV absorbers to enhance the overall protective effect.

Improve the production process

Strict control of vulcanization conditions: Overvulcanization can lead to rubber aging problems, and the vulcanization temperature and time should be optimized.

Mixing uniformity: avoid too many or too few local components to ensure that the anti-aging agent is evenly distributed.

Improved thermal oxidation in processing: Reduced air contact during compounding and vulcanization, reducing the risk of oxidation.

Surface protection measures

Surface coating: Apply anti-aging coatings (such as polyurethane coatings, and silicon-oxygen coatings) to rubber products to form a physical barrier.

Spray protective fluid: Spray a liquid containing antioxidants to delay the aging process.

Surface coating: Metal coatings or composite coatings are used to improve UV resistance.

Control of environmental factors

Protect from light: Reduce UV radiation, such as using light-out packaging or storing in the dark.

Moisture-proof: control the ambient humidity to avoid moisture and promote the aging of rubber.

Low-temperature storage: Storing rubber products in a low-temperature environment can slow down the rate of aging.

Avoid contact with active substances: Avoid contact with oils, organic solvents, acids, and alkalis, which can accelerate the aging of rubber.