Why Are TPU and CPU Prepolymers Used Differently in Casting?
Polyurethane prepolymer casting can be divided into two main types based on the material system: Thermoplastic Polyurethane (TPU) and Castable Polyurethane (CPU). Although both originate from polyurethane prepolymers, their processing methods and resulting properties are quite different.
TPU casting involves heating thermoplastic polyurethane to a molten state and pouring it into molds, where it solidifies upon cooling. The material is flexible, elastic, and resistant to abrasion, impact, and many chemicals. These properties make TPU suitable for components like soft wheels, seals, gaskets, and other flexible parts. The thermoplastic nature of TPU allows some reprocessing or adjustment during production, but careful temperature and mold control are necessary to prevent degradation and maintain consistent quality.
CPU casting, on the other hand, uses reactive, thermosetting prepolymers that cure chemically inside the mold. Once cured, CPU cannot be remelted. The formulation of CPU can be precisely adjusted to control hardness, elasticity, and other mechanical properties, making it ideal for high-load applications such as industrial rollers, bushings, pads, and structural components. CPU also allows for complex shapes and fine details, and it can bond well to embedded inserts, which is important for durable and precise parts.
The choice between TPU and CPU in prepolymer casting is closely related to the intended application, including factors such as flexibility, hardness, wear resistance, and the need for dimensional stability. Each system offers distinct advantages depending on the specific requirements of the part and the manufacturing process, shaping how polyurethane components are designed and produced.