What should be noted when optimizing the sealing ring formula?

The optimization of the sealing ring formula should be comprehensively considered from six core dimensions: material selection, vulcanization system, reinforcing filling system, softener and antioxidant, process compatibility, and economy. The specific analysis and suggestions are as follows:

I. Material Selection: Adaptation to Working Conditions is the Foundation

Media Compatibility

Oil-based media: Preferentially select nitrile rubber (NBR), which has excellent oil resistance; if the temperature exceeds 150°C, it is necessary to upgrade to hydrogenated nitrile rubber (HNBR) or fluororubber (FKM).

Chemical Corrosion Media: Fluororubber (FKM) is suitable for strong acid and strong alkali environments; silicone rubber (VMQ) is resistant to extremely low temperatures, but has poor oil resistance and needs to avoid contact with oil.

Dynamic Sealing: In addition to media compatibility, extra attention should be paid to wear resistance. For example, blending nitrile rubber with polyurethane (PU) can enhance wear resistance.

Temperature and Pressure Adaptation

High Temperature Environment: Silicone rubber (VMQ) has a temperature range of -100°C to 250°C, while fluororubber (FKM) can withstand temperatures above 200°C.

High Pressure Conditions: The hardness of the sealing ring needs to be increased (such as Shore A hardness of 85-90) to enhance the compressive resistance, but a balance must be maintained between elasticity and wear resistance.

II. Vulcanization System: Balance Performance and Process

Vulcanization Type Selection

Sulfur Vulcanization: Low cost and mature process, but poor heat resistance. Suitable for routine conditions.

Peroxide Vulcanization (such as DCP): Excellent heat resistance and low-temperature resistance, small compression permanent deformation, but low elongation. It is necessary to optimize performance through a composite vulcanization system (such as DCP + sulfur + accelerator).

Low or No Sulfur Blends: Reduce vulcanization backreaction and improve heat resistance, suitable for high-temperature dynamic sealing.

Vulcanization Parameter Control

Temperature and Time: Excessive vulcanization temperature will cause rubber decomposition, while too low a temperature will result in insufficient vulcanization. For example, the vulcanization temperature of nitrile rubber is usually 150-180°C, and the time needs to be adjusted according to the thickness.

Pressure Management: Insufficient vulcanization pressure may cause bubbles, while excessive pressure may lead to mold damage. It is necessary to adjust the pressure dynamically according to the hardness of the rubber and the size of the mold.

III. Reinforcement and Filling System: Enhance Hardness and Wear Resistance

Carbon Black Selection

High Wear Resistance Carbon Black (HAF): Significantly improves wear resistance and strength, suitable for dynamic sealing.

Spray Carbon Black: Gives the rubber good elasticity, reduces compression permanent deformation, but requires a large amount of filling (such as more than 120 parts) to achieve high hardness, which may affect processing performance.

Carbon Black Blending: For example, blending high wear resistance carbon black with semi-reinforcing carbon black can balance wear resistance and elasticity.

Application of Nano Fillers

Nano Silica (SiO?): Improves tensile strength and wear resistance, but the dosage needs to be controlled to avoid agglomeration.

Carbon Nanotubes (CNTs): Enhances conductivity and wear resistance, suitable for special conditions (such as electromagnetic sealing).

IV. Softeners and Antioxidants: Optimize Processing and Durability

Softener Selection

Low Molecular Weight Polyester: Good weather resistance, can improve elasticity without significantly reducing wear resistance.

Epoxy Soybean Oil: Environmentally friendly plasticizer, but may slightly affect wear resistance, need to balance according to the working conditions.

Antioxidant Combination

Antioxidant (such as 4010NA): Inhibits oxidation degradation, improves heat resistance against aging.

Anti-Ozone Agent (such as IPPD): Prevents ozone erosion, extends the service life of the sealing ring in outdoor use.

Ultraviolet Absorber: Protects the sealing ring from photo-oxidation damage, suitable for outdoor equipment.

V. Process Adaptability: Ensure the Feasibility of the Formula

Mixing Process Optimization

When filling a large amount of carbon black, the mixing time needs to be extended and the temperature increased (such as above 145°C), to ensure uniform dispersion of the fillers and avoid scorching.

Nano fillers need to be treated by surface modification (such as silane coupling agent treatment) to improve compatibility with the rubber.

Mold and Molding Process

Precision mold design: Reduce burrs and size deviations, avoid distortion or deformation of the sealing ring during installation.

Injection Molding: Suitable for complex-shaped sealing rings, can reduce flash and internal defects, and improve production efficiency.

VI. Economy and Environmental Friendliness: Balance Cost and Sustainability

Cost Optimization While meeting the performance requirements, it is preferable to select materials with higher cost-effectiveness (such as replacing some fluorine rubber with nitrile rubber).

By adding low-cost fillers (such as calcium carbonate) to reduce the raw material cost, the dosage should be controlled to avoid performance degradation.

Environmental compliance

Avoid using toxic plasticizers (such as phthalate esters), and choose environmentally friendly alternatives (such as polyester plasticizers).

Comply with environmental regulations such as RoHS and REACH, and reduce the use of heavy metals and harmful substances.

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