What is the material used for flexible rubber expansion joint.

Flexible rubber expansion joints are used for pipeline vibration and noise reduction and compensation displacement joints. Appearance looks like they are made of rubber, so what material is used in the end?
Flexible rubber expansion joint sphere is composed of an inner rubber layer, reinforced layer with multiple layers of scraped rubber nylon cord fabric, outer rubber layer composite rubber tube. According to the different media used in the rubber material is different, there are natural rubber, butyl rubber, butyl rubber, nitrile rubber, EPDM rubber, neoprene, silicone rubber, fluorine rubber, etc.. They have heat resistance, acid resistance, alkali resistance, corrosion resistance, wear resistance, oil resistance and other functions.
In general, if the grease solution and natural rubber for a long time in contact with the case of easy to cause the loosening of rubber molecules, performance in the sphere surface that will cause the local expansion of the sphere, luoying flexible rubber expansion joint using fluorine rubber (FKM) containing fluorine monomer copolymerization and organic elasticity, high temperature resistance can also have reached 300 ℃, acid and alkali resistant oil resistant chemical corrosion resistance is good FKM has good overall performance, but the disadvantage is that it is expensive, poor reprocessability, and insufficient cold resistance.
Silicone rubber main chain contains the presence of silicon atoms, more stable performance, high temperature resistance and low temperature resistance is currently one of the raw materials of good resistance to large temperature difference flexible rubber joints, the stability of thermal oxidation and ozonation is very good, chemical inertia.