What are the common bladder materials used in accumulator construction, and how do they impact performance?

Accumulators are devices used to store potential energy in the form of a pressurized fluid. The bladder is a crucial component in accumulator construction, as it separates the hydraulic fluid from a compressible gas, usually nitrogen. The choice of bladder material can significantly impact the performance and reliability of the accumulator. Common bladder materials include:
Butyl Rubber:
Characteristics: Butyl rubber is known for its excellent gas impermeability, chemical resistance, and low gas permeation rates. It is also resistant to ozone and weathering.
Impact on Performance: Butyl rubber bladders are suitable for applications where low gas permeation is critical, and resistance to environmental factors is required.
Hydrogenated Nitrile Butadiene Rubber (HNBR):
Characteristics: HNBR offers improved chemical resistance and high-temperature stability compared to standard nitrile rubber. It is often used in applications where exposure to oil, fuel, or harsh chemicals is a concern.
Impact on Performance: HNBR bladders are chosen for applications where resistance to specific chemicals or oils is necessary, ensuring long-term durability.
Nitrile Rubber (NBR):
Characteristics: Nitrile rubber provides good resistance to oils, fuels, and hydraulic fluids. It is known for its flexibility and resilience.
Impact on Performance: NBR bladders are commonly used in hydraulic accumulators for general-purpose applications where resistance to oils and flexibility are important.
Ethylene Propylene Diene Monomer (EPDM):
Characteristics: EPDM is known for its excellent resistance to weathering, ozone, and ultraviolet (UV) radiation. It also has good electrical insulating properties.
Impact on Performance: EPDM bladders are suitable for outdoor or exposed applications where resistance to environmental factors is crucial.
Fluoroelastomers (Viton):
Characteristics: Fluoroelastomers, commonly known by the brand name Viton, provide exceptional chemical resistance, high-temperature stability, and resistance to aggressive fluids.
Impact on Performance: Viton bladders are chosen for applications involving extreme temperatures, aggressive chemicals, or where a high level of chemical resistance is required.
Polyurethane:
Characteristics: Polyurethane is valued for its high tensile strength, abrasion resistance, and flexibility. It can be formulated to provide specific properties such as low-temperature flexibility or resistance to hydrolysis.
Impact on Performance: Polyurethane bladders are used in applications where a balance of strength, flexibility, and resistance to wear and tear is important.
The choice of bladder material depends on the specific requirements of the application, including the type of hydraulic fluid, environmental conditions, temperature range, and chemical exposure. Proper selection ensures optimal performance, longevity, and safety of hydraulic accumulators.