What material is used for seal rings?

Here's a simple explanation of commonly used materials for seal rings:

1. Rubber Family: The Flexible and Durable Basics

▸ Nitrile Rubber (NBR): Like an "oil-resistant workhorse"
Strengths: Resistant to oil and gasoline, inexpensive and durable
Applications: Automotive engine oil seals, hydraulic pipe fittings
Weaknesses: Prone to cracking after prolonged exposure to UV rays
▸ Fluororubber (FKM/Viton): The "Special Forces" of the Chemical Industry
Strengths: Resistant to strong acids and high temperatures (200℃+), corrosion resistant
Applications: Chemical plant pumps and valves, aerospace engines
Weaknesses: Expensive, slightly less elastic
▸ Silicone Rubber: The "calm guy" of temperature changes
Strengths: Unaffected by temperatures from -50℃ to 250℃, food-grade safe
Applications: Coffee machine seals, medical equipment
Weaknesses: Easily swells when soaked in oil

2. Plastic Elites: The Hard-Bone of Wear and Resilience

▸ Polytetrafluoroethylene (PTFE/Teflon): The Smooth "Non-Stick King"
Strengths: Surface so smooth it doesn't stick to dirt, resistant to almost all chemicals
Applications: Chemical pipeline sealing, food machinery
Weaknesses: Poor elasticity, often requires springs for support
▸ Polyurethane (PU): The "Tough Guy" Under Pressure
Strengths: Wear-resistant and pressure-resistant, like an upgraded version of tire rubber
Applications: Excavator hydraulic cylinders, high-pressure valves
Weaknesses: Prone to hydrolysis and powdering in humid and hot environments

3. Metals and Composite Materials: The "Saviors" of Extreme Environments

▸ Metal-Coated Rubber: Explosion-Proof Experts
Structure: Outer stainless steel shell + inner rubber core
Strengths: Resistant to high-pressure extrusion, explosion-proof
Applications: Oil drilling equipment, high-pressure reactors
▸ Graphite-Filled Sealing Rings: The "Firefighter" of High Temperatures
Strengths: Does not melt at 800℃, self-lubricating
Applications: Engine exhaust pipes, high-temperature valves

4. Key to Material Selection in One Sentence

▸ When choosing sealing ring materials, consider three points:
What liquid will it be soaked in? → Choose nitrile rubber for oily surfaces, fluororubber for acidic surfaces.
How will it change temperature? → Use silicone for large temperature differences, graphite for ultra-high temperatures.
Dynamic or static? → Use polyurethane for rotating shafts, PTFE for static seals.
▸ Avoid these pitfalls:
Don't use ordinary rubber instead of fluororubber in car repairs → It will deteriorate after three days in gasoline.
Food factories must choose non-toxic white materials for sealing → Gray industrial materials will cause pollution.