Polyurethane seals are one of the most versatile and durable materials used in fluid dynamic seals, such as pump shaft seals and hydraulic cylinder piston and piston rod seals. This material has many chemical formulas, so it can be applied to many working conditions.
Hallite 606 Single acting, single lip asymmetric piston seal with easy installation and low temperature performance
1, high strength and toughness
Due to their good hardness and toughness, polyurethane seals have excellent resistance to extrusion. In addition, good hydraulic seals must resist shear and tear. Under the action of pressure, hydraulic oil can easily break through the defense lines of inferior seals. Polyurethane deforms under pressure to adapt to changes in the gap to ensure reliable sealing; when the pressure is removed, its high strength allows it to return to its original shape without permanent deformation.
2, high wear resistance
Oil contamination is a common symptom of hydraulic systems. When particulate matter abrades a seal, the seal is at risk of premature failure. Polyurethane benefits from naturally high wear resistance, especially compared to other polymers such as nitrile rubber and fluoroelastomer.
3, high temperature resistance
Under high temperature conditions, polyurethane is still the first choice for high-pressure hydraulic systems. Polyurethane is rated for temperatures in excess of 120°C while also being able to withstand pressures of 5000 psi and higher, an extreme combination that makes polyurethane the best in its class for hydraulic cylinders. Although fluororubber can easily handle temperatures above 200°C, its pressure-bearing capacity is poor and is usually limited to 2000psi or even lower.
4, processability
Because polyurethane seals are not cast from a liquid base or formed in one go, but can be processed directly on a CNC lathe, they can be processed into more complex shapes.
With advances in advanced polymer formulations and manufacturing technologies, new high-performance seals will drive further development of hydraulic technology toward ultra-high pressure. For example, previous urethanes were prone to hydrolysis when operating in aqueous hydraulic fluids, especially when operating at high temperatures. The current advanced polyurethane polymers are completely resistant to hydrolysis, thus improving the previous shortcomings. As polyurethane technology advances, it is expected that this material can cover almost all hydraulic sealing applications.
(Wang Xin)