Hydraulic Seal Materials - General Information

　　The majority of hydraulic seals and pneumatic seals are made from elastic materials. These are all polymers (macromolecules) which differ in how their chain molecules are connected. Basically there are two material groups:

　　• Elastomers: rubber-elastically deformable polymers and thermoplastic elastomer-thermoplastics which can be deformed elastically within a defined temperature range.

　　• Plastomers: plastically deformable polymers.

　　The most important factor property of a material for sealing is its elasticity . It enables the material to have the capability of changing shape without disrupting the cohesion of its molecules. Elasticity gives seals their two most important properties:

　　• to adapt to the changing profile of the sealed surfaces

　　• to react automatically to pressure changes by altering the contact pressure.

　　The following are important properties to be considered when selecting a seal material:

　　mechanical

　　• tensile strength and hardness

　　• resistance to abrasion

　　• sliding and friction properties

　　• flexibility and resilience

　　• compression set and elongation

　　thermal

　　• temperature resistance

　　• caloric

　　• thermal expansion

　　• joule effect

　　• softening

　　physical and chemical

　　• compatibility with media

　　• swelling

　　• aging

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