Polyurethane rubber (PU), whose full name is polyurethane elastomer, is a polymer material that falls between rubber and plastic, boasting excellent mechanical strength and superior wear resistance.
PU exhibits extremely high tensile strength and tear resistance, with its tear strength significantly surpassing that of most general-purpose rubbers. Additionally, its wear resistance is 3-5 times that of natural rubber, earning it the title of "king of wear-resistant rubber". It is particularly suitable for dynamic sealing applications involving high friction and wear.
PU exhibits excellent oil resistance and chemical resistance, demonstrating outstanding durability against mineral oil, fuel oil, hydraulic oil, and non-polar solvents, allowing it to operate in oil-containing media for extended periods. However, it is not resistant to strong acids, strong alkalis, hot water, and polar solvents such as dimethylformamide.
Polyurethane rubber exhibits an exceptionally wide range of hardness, spanning from Shore A15 (extremely soft) to Shore D90 (resembling hard plastic), while still maintaining good elasticity even at high hardness levels. It exhibits minimal compression set and high load-bearing capacity, making it suitable for high-pressure hydraulic systems and heavy-duty sealing applications.
The typical operating temperature range for PU is from -40℃ to +85℃, with special high-temperature resistant formulations reaching up to +120℃ and low temperature resistance down to -50℃. Compared to most rubbers, PU has moderate heat resistance and is not suitable for long-term use in dry heat environments above 100℃.In addition, polyurethane rubber exhibits excellent ozone aging resistance and radiation resistance, and can be customized to achieve various functionalities such as transparency, flame retardancy, and conductivity through formulation adjustments. However, regular PU is not resistant to hydrolysis, and polyether-based PU or specialized hydrolysis-resistant grades should be selected for use in humid and high-temperature environments.
PU seals, which are sealing rings made of polyurethane rubber, play a pivotal role in hydraulic, pneumatic, and dynamic sealing systems across multiple industries due to their high wear resistance, high strength, and excellent oil resistance.
Construction Machinery and Hydraulic Systems: In hydraulic cylinders, piston rod seals, dust seals, and support rings of heavy machinery such as excavators, loaders, and cranes, PU seals have significantly improved the sealing life due to their high pressure resistance, extrusion resistance, and low friction characteristics. It is one of the preferred materials for hydraulic reciprocating motion seals.
Pneumatic systems and automation equipment: In cylinder piston seals, valve seals, air compressors, and pneumatic pipeline connectors, PU sealing rings, due to their good resilience, wear resistance, and low sliding resistance, can ensure no leakage for over a million reciprocating actions. Meanwhile, PU dustproof rings can effectively prevent external dust and sand particles from entering the system.
Automotive manufacturing: PU seals are widely used in automotive shock absorber seals, power steering systems, brake system piston seals, and some oil circuit connections. Their resistance to mineral oil and fuel, as well as their ability to resist vibration wear, enhance the reliability and durability of automotive chassis.
High and ultra-high pressure applications: In hydraulic jacks, hydraulic torque wrenches, ultra-high pressure water jet equipment, and injection molding machine clamping systems, PU sealing rings (especially when equipped with retaining rings) can withstand ultra-high pressures exceeding 70 MPa, and their tear resistance and extrusion resistance are superior to most ordinary rubbers.
Precision instruments and office equipment: In photocopiers, printers, optical instruments, and precision pneumatic control valves, small PU seals and diaphragms are used to transmit motion and provide sealing. They exhibit dimensional stability, low wear, and do not contaminate the interior of the equipment.
Sports equipment and general machinery: In ski pole grips, roller skate brake pads, conveyor belt guides, industrial rubber rollers, and water pump dust covers, the high wear resistance of PU material also makes it an excellent sealing and protective component.
In summary, polyurethane rubber materials and their PU seals play an irreplaceable role in fields such as construction machinery, hydraulic and pneumatic systems, automobile manufacturing, high-pressure equipment, and precision instruments due to their superior wear resistance, high tear resistance, excellent oil resistance, and wide range of adjustable hardness. They are high-performance materials tailored for demanding dynamic sealing conditions.