Why are the colors of the sealing rings different?

The reasons for the different colors of the sealing rings mainly involve multiple factors such as material composition, functional requirements, production processes, industry standards, and user preferences. Here is a detailed analysis:

1. Material composition differences

Base polymer: Sealing rings are usually made of rubber (such as nitrile rubber NBR, fluorine rubber FKM, silicone rubber VMQ, etc.) or plastic (such as polytetrafluoroethylene PTFE). Different polymers have different colors by nature, for example:

Nitrile rubber (NBR) is usually black or dark in color due to the presence of carbon black reinforcing agent.

Fluorine rubber (FKM) may be brown or black due to its high-temperature and chemical corrosion resistance formula.

Silicone rubber (VMQ) is often transparent or white due to its high purity.

Additives: To improve performance (such as oil resistance, aging resistance, anti-static), carbon black, titanium dioxide, zinc oxide, etc. are added. These additives can change the color, for example, carbon black makes the material black, titanium dioxide may produce white or light colors.

2. Functional requirements

Temperature resistance: Sealing rings used in high-temperature environments (such as fluorine rubber) may add special pigments to enhance heat resistance, and the color may be darker.

Chemical resistance: Sealing rings in contact with strong acids, strong alkalis or solvents may adopt specific formulas, and the color may change due to the requirements of chemical stability.

Food grade/Medical grade: Sealing rings that need to meet hygiene standards (such as silicone rubber) may be transparent or white to show no impurities.

Ultraviolet resistance: Sealing rings used outdoors may add ultraviolet absorbers, and the color may be yellowish or brown to block ultraviolet rays.

3. Production process

Sulfurization process: During the rubber sulfurization process, temperature, time, and type of sulfurizing agent affect the color. For example, over-sulfurization may cause the color to darken.

Uniform mixing: Inhomogeneous distribution of pigments may cause color differences, especially in batch production.

Mold design: Surface treatment of molds (such as polishing, sandblasting) may affect the surface gloss of the sealing ring, which indirectly affects the visual color.

4. Industry standards and certifications

Color coding: Some industries (such as automotive, aerospace) may use colors to distinguish sealing ring specifications or performance grades. For example:

Black: Universal type, resistant to oil and temperature.

Green: Resistant to low temperatures or special media.

Red: For high-pressure or high-speed applications.

Certification requirements: Sealing rings certified by organizations such as FDA (Food and Drug Administration) may limit the types of pigments, resulting in a single color.

5. User preferences and brand identification

Brand recognition: Manufacturers may distinguish product lines or brands through colors. For example, all sealing rings of a certain brand are blue to enhance recognition.

Application scenarios: Users may choose the color of the sealing ring based on the color of the equipment or aesthetic needs, such as using white sealing rings inside white household appliances.

6. Environmental factors

Aging and fading: Long-term exposure to light, high temperature or chemical environments may cause the color of the sealing ring to fade or turn yellow, but the initial color design takes durability into consideration.

Example explanation

Black sealing ring: Commonly used in the engine compartment of cars, as NBR (Nitrile Butadiene Rubber) is resistant to oil and carbon black enhances wear resistance.

White sealing ring: Often used in food processing equipment, as VMQ (Viton Metallocene) rubber is non-toxic and transparent.

Red sealing ring: May be used in high-pressure hydraulic systems, where red pigments are added to the fluorine rubber (FKM) formula to indicate high-pressure performance.

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