Custom Molded Polyurethane Wheel

Our company was founded in 2007 and has been dedicated to the research, development, production, and sales of polyurethane products since its establishment. We are located in Yantai, Shandong - the birthplace of polyurethane products in China - which gives us unique advantages in technical support and technological innovation. After nearly 20 years of development, we have built a strong technical team, production team, and sales team. We also have multiple casting production equipment and testing equipment to ensure the quality requirements of every stage in the production of custom molded polyurethane wheel. We support OEM.

The production process for custom molded polyurethane wheel is predominantly based on cast polyurethane casting. The core process includes: mold preparation and pretreatment → raw material preparation and prepolymer synthesis → degassing and mixing → casting → vulcanization/curing → demolding → post-processing.

1.Raw Material Preparation and Prepolymer Synthesis

Raw material selection: Commonly used polyisocyanates (such as TDI and MDI) are reacted with polyols (polyester or polyether type). For high-performance wheels, the TDI/MOCA system is still widely used because of its longer pot life, which can effectively reduce bubbles and short-shot defects; whereas the MDI system may cause casting defects due to too rapid an increase in viscosity.

Prepolymer synthesis: The dehydrated polyol is reacted with isocyanate at 70–90°C for 2–4 hours to form a prepolymer containing a certain amount of free isocyanate groups (NCO%).

2.Degassing and Mixing

Vacuum degassing: The prepolymer and the chain extender in the formulation (such as MOCA) need to be vacuum degassed at 75–110°C to remove moisture and dissolved gases, preventing bubbles inside the product.

Mixing and casting: Components A (prepolymer) and B (chain extender/curing agent) are mixed uniformly at high speed in the mixing head of the casting machine according to the precise ratio.

3.Casting and Mold Preparation

Mold pretreatment: Clean the mold and spray a release agent. If a wheel with a bearing or hub needs to be formed, the bearing unit or hub must be pre-placed and positioned in the mold cavity to ensure that the polyurethane can encapsulate and secure the insert during casting.

Casting operation: The mixed material is poured into a preheated mold (usually 80–110°C). For more complex wheels, slow casting or centrifugal casting helps to expel air and fill fine structures.

4.Vulcanization and Demolding

Vulcanization: After casting, the mold is heated and cured in an oven at 100–110°C for 30–40 minutes so that the material initially sets.

Demolding and post-vulcanization: After demolding, the product needs to continue "post-vulcanization" at 100–105°C for 22–24 hours to fully complete the crosslinking reaction and achieve optimal physical properties.

5.Post-processing

After cooling, custom molded polyurethane wheel is machined as needed, such as by turning and grinding, to correct dimensions or remove flash. If shrinkage cavities or bubbles occur due to improper process control, rework may be required.

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