O-ring FDA certified food-grade rubber ring Suzhou sealing ring manufacturer
Silicone rubber is divided into heat-curing type and room temperature curing type. Heat-curing types include methyl silicone rubber (MQ), methyl vinyl silicone rubber (VMQ, the most widely used with numerous product grades), methyl vinyl phenyl silicone rubber (PVMQ, resistant to low temperatures and radiation), as well as nitrile silicone rubber and fluorosilicone rubber, among others. MQ is a colorless, transparent, highly viscous, plastic linear polymer compound, with a backbone composed of silicon and oxygen atoms, and methyl groups attached to the silicon atoms. Its molecular weight ranges from 500,000 to 800,000. VMQ is a colorless, transparent, highly viscous, plastic linear polymer compound, with a backbone composed of silicon and oxygen atoms, and methyl and vinyl groups attached to the silicon atoms. Its molecular weight ranges from 500,000 to 800,000. PVMQ is obtained by introducing diphenyl siloxane segments or methylphenyl siloxane segments into the molecular chain of vinyl silicone rubber.
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Temperature range: -60°C (special down to -115°C) to 204°C (special up to 260°C)
O-ring material selection: Silicone rubber
Silicone rubber refers to rubber whose backbone consists of alternating silicon and oxygen atoms, with silicon atoms typically bonded to two organic groups. Ordinary silicone rubber mainly consists of siloxane segments containing methyl groups and a small amount of vinyl groups. The introduction of phenyl groups can improve the high and low-temperature resistance of silicone rubber, while the introduction of trifluoropropyl and cyano groups can enhance its temperature and oil resistance.

Silicone rubber has good low-temperature resistance and can generally operate at -55°C. With the introduction of phenyl groups, it can withstand temperatures as low as -73°C. Silicone rubber also excels in heat resistance, operating long-term at 180°C and withstanding temperatures slightly above 200°C for several weeks or longer while retaining elasticity. It can momentarily endure temperatures above 300°C. Silicone rubber has excellent gas permeability, with an oxygen transmission rate that is among the highest in synthetic polymers. Additionally, silicone rubber is physiologically inert and does not cause blood clotting, making it widely used in medical applications.

High-temperature performance. The most notable feature of silicone rubber is its high-temperature stability. Although its strength at room temperature is only half that of natural rubber or some synthetic rubbers, at temperatures above 200°C, silicone rubber can maintain a certain degree of flexibility, resilience, and surface hardness, with no significant changes in mechanical properties.
Properties
1. Low-temperature performance. The glass transition temperature of silicone rubber is generally between -70°C and -50°C, with special formulations reaching -100°C, indicating excellent low-temperature performance. This is highly significant for the aviation and aerospace industries.
2. Weather resistance. The Si-O-Si bonds in silicone rubber are highly stable against oxygen, ozone, and ultraviolet light, providing excellent weather resistance without the need for additives.
3. Electrical properties. Silicone rubber has outstanding insulation properties, with excellent corona and arc resistance.
4. Physical and mechanical properties. At room temperature, the physical and mechanical properties of silicone rubber are inferior to those of general-purpose rubbers. However, at high temperatures of 150°C and low temperatures of -50°C, its physical and mechanical properties surpass those of general-purpose rubbers.
5. Oil and chemical resistance. Ordinary silicone rubber has moderate resistance to oil and solvents.
6. Gas permeability. At room temperature, the permeability of silicone rubber to gases such as air, nitrogen, oxygen, and carbon dioxide is 30-50 times higher than that of natural rubber.