Food grade seal [rubber]
Silicone rubber O-ring is a common food grade O-ring. Physical and chemical properties of silicone rubber: silicone material is a kind of saturated non-polar rubber based on the silicon element obtained from quartz, and formed by the adhesion of silicon atoms to side chains such as methyl and vinyl. Different side chains lead to different properties of silicone rubber. Methyl vinyl silicone rubber (VMQ) is a kind of silicone O-ring material which is widely used. Food grade silica gel O-ring has excellent heat resistance, low temperature elasticity, especially excellent oxidation resistance and ozone resistance, high permeability and gas permeability selectivity. Good electrical insulation performance (volume resistance is more than 1016 Ω. Cm, breakdown voltage is more than 30 kV / mm), corona resistance and arc resistance. However, with the addition of conductive carbon black, nickel powder, aluminum powder and silver powder, proper conductivity can be obtained (the volume resistance can reach 5-0.02 ohm. Cm). Silicone rubber is hygroscopic and can be used for isolation. Water resistance, but poor water vapor resistance, pressure more than 50 psi is not recommended. Compatible with most oils, chemicals and solvents. Generally, silicone rubber has good acid and alkali resistance, good resistance to polar solvents, and is not resistant to alkane hydrogen and aromatic oil products. It is not recommended to use in most concentrated solvents, oil products, concentrated acids and diluted caustic soda solutions. Special silicone rubber also has radiation resistance, fire resistance, oil resistance and other properties. Its tensile strength is low and its wear resistance is weak, so it is generally not used for dynamic sealing.
Molecular structure of silicone rubber:
CH3 CH=CH
- (Si-O) (Si-O) methyl vinyl silicone rubber O-ring
CH3 CH3
O-type rubber seal ring of other materials:
I. food grade NBR rubber O-ring: suitable for use in petroleum hydraulic oil, glycol hydraulic oil, diester lubricating oil, gasoline, water, silicon grease, silicon oil and other media. It is a rubber seal with wide application and low cost. Not suitable for polar solvents, such as ketones, ozone, nitrohydrocarbons, MEK. Generally, the temperature range is - 40 ~ 120 ℃. Heat resistance, cold resistance, oil resistance, water tightness, wear resistance, chemical resistance, deformation resistance, mechanical property, strong tensile strength, 10 years.
2. Food grade HNBR hydrogenated Buna rubber O-ring: it has excellent corrosion resistance, tear resistance and compression deformation resistance, ozone resistance, sunlight resistance and weather resistance. It has better wear resistance than NBR. It is suitable for washing machine, automobile engine system and refrigeration system using new environmental protection refrigerant R134a. It is not recommended to use in alcohol, ester or aromatic solution. Generally, the temperature range is - 40 ~ 150 ℃.
III. food grade SIL silicone rubber O-ring: excellent heat, cold, ozone and atmospheric aging resistance. It has good insulation performance. However, the tensile strength of rubber is worse than that of general rubber and does not have oil resistance. It is suitable for household appliances such as electric water heater, electric iron, microwave oven, etc. It is also suitable for all kinds of articles in contact with human body, such as water bottles, drinking fountains, etc. It is not recommended to use in most concentrated solvents, oil products, concentrated acids and sodium hydroxide. Generally, the temperature range is - 55 ~ 250 ℃. Environmental protection, ozone resistance, weather resistance, heat resistance, cold resistance, chemical resistance, oil resistance, wear resistance, deformation resistance, 30 years.
IV. food grade Viton fluororubber O-ring: superior to silicone rubber in high temperature resistance, excellent weather resistance, ozone resistance and chemical resistance, but poor in cold resistance. Resistant to most oils and solvents, especially acids, aliphatic hydrocarbons, aromatic hydrocarbons, animal and vegetable oils. It is suitable for sealing requirements of diesel engine, fuel system and chemical plant. It is not recommended to use in ketones, low molecular weight esters and mixtures containing nitrate. Generally, the temperature range is - 20 ~ 250 ℃. Ozone resistance, weather resistance, water tightness, wear resistance, fire resistance, strong tensile strength, heat resistance, cold resistance, chemical resistance, oil resistance, wear resistance, deformation resistance, 30 years.
V. food grade FLS fluorosilicone rubber O-ring: its performance has the advantages of both fluorosilicone rubber and fluorosilicone rubber, with good oil resistance, solvent resistance, fuel oil resistance and high and low temperature resistance. It can resist the attack of oxygenated compounds, aromatic solvents and chlorinated solvents. It is generally used for aviation, aerospace and military purposes. Exposure to ketones and brake oil is not recommended. Generally, the temperature range is - 50 ~ 200 ℃.
