PU rods (polyurethane rods) are thermosetting elastomer rods made of polyurethane (PU) as the base material. They are cured and formed by the polymerization reaction of polyols and isocyanates to form materials with unique molecular structures. Polyurethane (PU) is a polymer material invented by German chemist Otto Bayer in 1937. Its main molecular chain contains repeated urethane groups (-NH-COO-). By adjusting the ratio of soft segments (flexible polyether or polyester) to hard segments (diisocyanate and chain extender), the hardness, elasticity, wear resistance and other properties of the material can be precisely controlled, making it a "universal material" between rubber and plastic.
The Shore hardness range of PU rods covers Shore A20 (super soft) to Shore D85 (super hard). It has both the high elasticity of rubber and the high strength of plastic. It is widely used in industrial fields with strict requirements on wear resistance, impact resistance, oil resistance and elasticity. It is an ideal substitute for traditional rubber, plastic and metal materials.
Advantages
Wear resistance
One of the core advantages of PU rods is that they have far superior wear resistance than traditional rubber and plastic. This feature stems from the synergistic effect of hard segments and soft segments in their molecular structure:
Hard segment (diisocyanate + chain extender): provides material rigidity, enhances intermolecular forces, and resists abrasive intrusion.
Soft segment (polyether/polyester): gives the material elasticity, absorbs impact energy, and reduces energy loss during wear.
Elasticity and impact resistance
The elastic modulus (0.5-50 MPa) of PU rods is between rubber (0.01-10 MPa) and plastic (1-10 GPa), and has both high resilience and high load-bearing capacity:
High resilience: The rebound rate of Shore A70 hardness PU rods can reach 40%-60% (the rebound rate of rubber is usually 30%-50%), and it can quickly return to its original state after repeated compression. It is suitable for scenes that require long-term pressure, such as cushions and spring replacements.
High impact resistance: Its energy absorption capacity (through the drop ball impact test) is 3-5 times higher than that of polyvinyl chloride (PVC) and 2-3 times higher than that of polyethylene (HDPE), which is suitable for safety protection fields such as explosion-proof housings and anti-collision guards.
Dynamic performance advantages
Fatigue resistance: Under cyclic compression/tensile loads (frequency 1Hz, amplitude ±10%), the life of PU rods can reach 10⁶-10⁷ times (rubber is only 10⁵-10⁶ times), which is suitable for high-frequency moving parts such as vibrating screens and conveyor belt rollers.
Low temperature elasticity: It can still maintain 70%-80% of normal temperature elasticity at -40℃ (rubber tends to become brittle below -20℃), which is suitable for low temperature scenes such as polar equipment and cold storage seals.
Chemical and oil resistance
The molecular structure of PU rods does not contain weakly polar carbon-carbon single bonds (such as PE and PP), but uses strongly polar urethane bonds (-NH-COO-) as the main chain, which makes it show excellent resistance to oils, solvents and chemical media:
Oil resistance: After immersion in hydraulic oil (ISO 32) and lubricating oil (SAE 10W-40) for 1000 hours, the volume expansion rate is <5% (ordinary rubber>20%), and the tensile strength retention rate is >85% (rubber<60%), which is suitable for oil seals, gear protective sleeves and other parts in contact with oil.
Solvent resistance: The tolerance to non-polar solvents (such as gasoline, diesel) and weakly polar solvents (such as acetone and ethyl acetate) is better than that of ordinary rubber (such as nitrile rubber), and there is no obvious decline in performance after short-term contact (<24h).
Acid and alkali resistance: It is resistant to weak acids (pH 4-6) and weak bases (pH 8-10), but it will degrade in strong acids (concentrated sulfuric acid, concentrated nitric acid) or strong bases (NaOH>30%), and it is necessary to improve chemical resistance through surface coating or composite materials (such as PU/PTFE).
Lightweight and easy processing
Low density: The density of PU rods is 1.1-1.3 g/cm³, which is only 1/7 of steel and 1/3 of aluminum. It can significantly reduce the weight of components and is suitable for automotive shock absorbing components, drone shells and other fields that are sensitive to weight reduction.
Easy to form and process:
Forming process: It can be formed by casting (CPU, thermosetting polyurethane) or extrusion (TPU, some thermoplastic polyurethane) process, and complex shapes (such as gears, seals) can be customized.
Secondary processing: It supports cutting, drilling, grinding, bonding (using polyurethane special glue) and other processing, and the edges can be chamfered or polished (surface roughness Ra≤3.2 μm).
Weather resistance and environmental adaptability
PU rods can significantly improve their outdoor durability by adding UV absorbers (such as benzotriazole), antioxidants (such as phenols) and hydrolysis agents (such as carbodiimide):
UV resistance: The yellowing index ΔYI <5 after 2000 hours of outdoor exposure (ΔYI of untreated PU rods can reach more than 20), suitable for roof waterproofing membranes and outdoor amusement facilities.
Hydrolysis resistance: Polyether PU rods (such as PTMEG-based) have a service life of 5-10 years in a humid environment (humidity 95%RH, 60℃), which is more suitable for high humidity environments such as ships and water conservancy projects than polyester PU (easy to hydrolyze).
PU rods achieve precise control of wear resistance, elasticity, oil resistance and other properties through the molecular structure design of soft and hard segments, becoming a high-performance alternative to traditional materials (rubber, plastic, metal) in the industrial field. Its wide application in wear protection, automobile, chemical, electronics, construction and other industries not only improves the service life and reliability of components, but also promotes the development of lightweight and functional integrated design.
