Ruitang Patent | How Does the Rotomolded Urea Tank Material Resist Corrosion by Urea Solution?

The Ruitang Patent column continues to interpret the authorized patents of Ruitang Plastic Group. In the previous issue, we focused on the municipal landscape traffic security track and interpreted the utility model patent for stone-like plastic bollards. In this issue, we turn to the supporting track of commercial vehicle exhaust aftertreatment, and introduce an invention patent for modified polyethylene material specially developed for the production of rotomolded urea tanks.

Patent Name: A Polyethylene Material for Rotomolded Urea Tanks and Its Preparation Method

Patent No.: ZL 2015 1 0535991.8

In the SCR exhaust aftertreatment system of commercial vehicles, the urea tank is a core liquid storage component for holding automotive urea solution. It is widely used in diesel heavy trucks, light trucks, construction machinery, buses and other power equipment. With the advantages of one-piece forming, weld-free structure and suitability for large hollow parts, rotomolding is the mainstream molding process for urea tanks.

However, throughout the whole process of raw material processing, tank molding and long-term vehicle operation, the industry has long been faced with a number of tough challenges:

▫️ Insufficient resistance to medium corrosion: Ordinary polyethylene tends to swell after long-term immersion in urea solution. Combined with continuous vehicle vibration, stress cracking is likely to occur, resulting in tank leakage and directly affecting the normal operation of the exhaust treatment system.

▫️ Poor low-temperature impact resistance: In the cold winter of northern China, urea tanks made of common PE lack toughness. Cracks and damage may easily occur under bumps and collisions during vehicle operation.

▫️ Narrow rotomolding processing window: Conventional modified formulations are highly sensitive to rotomolding temperature and rotating speed. It is difficult to control the uniformity of wall thickness during molding, and defects such as material shortage, bubbles and poor fusion are common, leading to low finished product yield.

▫️ Poor long-term weathering stability: Repeated high and low temperature cycles and sunlight aging will continuously degrade material performance and shorten the service life of urea tanks.

▫️ Weak process adaptability: Most modified materials on the market are developed for extrusion and injection molding. Their rheological properties do not match the requirements of rotomolding powder molding and cannot be directly used for rotomolded urea tank production.

To solve the above industry pain points, relying on years of experience in polyolefin modification and rotomolding material R&D, the Ruitang Plastic Group R&D team has developed this special modified polyethylene composite material for rotomolded urea tanks and obtained the invention patent authorization.

Core Technical Highlights of This Patent

✅ Compound modification system to resist corrosion of urea solution. The synergistic effect of resin combination and functional additives inhibits the penetration of urea solution into the material, reduces swelling effect and lowers the risk of stress cracking, so as to solve the urea tank leakage problem from the material source.

✅ Excellent low-temperature toughness for vehicle operation in cold regions. The optimized polymer chain structure greatly improves low-temperature impact strength. The tank is not easy to crack under vibration and impact in low-temperature environments, meeting the supporting needs of commercial vehicles in various regions.

✅ Optimized rheological properties for rotomolding and wider processing window. The melting and flow characteristics of powder fit the rhythm of rotational molding. Uniform wall thickness can be obtained after molding, reducing defects such as bubbles and material shortage and lowering the rejection rate of finished products.

✅ Long-lasting weather resistance and anti-aging performance for outdoor vehicle service. The compound anti-aging system resists degradation caused by ultraviolet rays, rainwater and alternating hot and cold conditions. The material is not prone to pulverization and embrittlement after long-term use to extend the service cycle of the tank.

✅ Stable formulation system to support mass production. The complete material preparation process is mature with controllable raw material ratio, enabling stable and continuous bulk supply and adapting to continuous production of rotomolding manufacturers.

Applicable Scenarios

Scenario 1: SCR urea tanks for heavy-duty trucks and long-haul freight vehicles

Suitable for exhaust aftertreatment liquid storage tanks of heavy trucks and tractors complying with China National VI and above emission regulations. Modified PE powder can be directly used for rotomolding. It adapts to bumpy and complex road conditions of long-distance freight to ensure long-term sealing and no leakage of urea tanks.

Scenario 2: Urea tanks for light trucks and blue-plate freight vehicles

Liquid storage containers matched with light-duty trucks. The one-piece rotomolded structure without welds realizes lightweight, balancing vehicle weight reduction and durability, suitable for urban distribution and short-distance freight scenarios.

Scenario 3: Urea tanks for construction machinery and non-road mobile machinery

Applied to excavators, loaders, bulldozers and other engineering equipment. The working environment features fierce vibration and large temperature difference between day and night. The material can withstand continuous impact and high-low temperature cycles, suitable for harsh working conditions such as mines and construction sites.

Scenario 4: Urea tanks for diesel-powered buses and coaches

Supporting exhaust treatment tanks for city buses and long-distance coaches. The integrated hollow structure provides reliable sealing, fits the chassis layout of buses and reduces the failure rate of exhaust systems.

Scenario 5: Aftertreatment liquid storage tanks for agricultural machinery

For tractors, harvesters and other agricultural diesel machinery. Agricultural equipment often suffers frequent bumps and long-term outdoor storage. The material features excellent urea corrosion resistance and weather resistance for agricultural machinery supporting production.

Scenario 6: Extended application to other rotomolded liquid storage containers resistant to chemical media

This modification formula can be applied to various rotomolded hollow storage tanks and chemical containers for weak polar aqueous solutions, including agricultural liquid fertilizer storage tanks and industrial diluent tanks.

Core Value for Customers

🔹 Solve the leakage problem of urea tanks and reduce after-sales risks for vehicle manufacturers. The material is optimized to resist urea swelling and stress cracking, reducing leakage maintenance and helping OEMs and aftertreatment system manufacturers cut after-sales compensation costs.

🔹 Broaden the rotomolding processing window and improve yield for product manufacturers. The rheological property is specially optimized for rotomolding, with higher tolerance to production parameters. It reduces defective products and waste materials, improves production efficiency of rotomolding factories and saves raw material consumption.

🔹 Adapt to working conditions across all regions and expand market coverage. Outstanding low-temperature toughness enables the produced urea tanks to steadily serve the cold northern market, helping manufacturers break regional performance restrictions and reach more customers.

🔹 Long-lasting weather resistance extends service life and builds good reputation. The anti-aging formula slows down material degradation under outdoor conditions. The durable performance of urea tanks enhances recognition from end customers for supporting parts.

🔹 Localized and stable material solution for independent and controllable supply chain. Self-developed modification formula realizes stable local supply, reduces dependence on imported special rotomolding raw materials, and balances product performance and procurement cost.

This invention patent represents Ruitang’s technical accumulation in the track of functional rotomolded materials for vehicles, as well as a special breakthrough of modified polyolefin rotomolding materials for commercial vehicle exhaust aftertreatment supporting parts. Ruitang’s R&D work is always based on the real demands of downstream rotomolding manufacturers and vehicle supporting enterprises. We combine polyolefin modification technology with rotomolding process in depth to overcome the shortcomings of ordinary PE materials such as poor urea corrosion resistance, easy cracking at low temperature and difficult processing. We provide customized rotomolded new materials to support the upgrading of commercial vehicle aftertreatment components.

The Ruitang Patent column will keep updating. Stay tuned for our next patent interpretation.

If you have practical experience or questions about material selection for rotomolded urea tanks and development of automotive rotomolded products, welcome to leave a comment and discuss with us.