TPU Injection Molding Process - Guangyuan Ruifeng New Materials

Category: Material Selection

Release Time: 2025-07-24

Summary: In other thermoplastic materials, when the processing temperature is higher than the melting temperature of the raw material

In other thermoplastic materials, when the processing temperature is higher than the melting temperature of the raw material, the melt mainly exhibits a viscous flow state. The higher the processing temperature, the better the flowability of the melt. When the processing temperature is lower, the flowability of the melt is poor, even not flowing, and the elasticity exhibited by the melt is relatively small. (TPU crosslinking agent manufacturer)

For elastomers such as TPU, when the processing temperature is higher than a certain temperature (virtual cross-linking between molecules is completely released), the flowability of the melt is better, and the melt exhibits more viscous flow; When the processing temperature is below a certain temperature (the virtual cross-linking between molecules is released), the melt exhibits both fluidity and elasticity, making it a viscoelastic material. (TPU crosslinking agent manufacturer)

When the temperature of the melt is high during injection molding, TPU, like other thermoplastic materials, mainly exhibits viscosity and flowability. The product can obtain a good shape, stable size, and small deformation. When the temperature of the melt is low, TPU exhibits viscoelasticity. Due to poor fluidity, the product does not naturally fill the mold cavity, but has a certain degree of elastic expansion to fill the mold cavity. When the injection pressure is released, the external force causing elastic expansion disappears, and the expanded part recovers deformation, resulting in a large shrinkage rate, smaller size, and greater deformation. (TPU crosslinking agent manufacturer)

Therefore, the adjustment of TPU injection molding process should pay attention to:

1. The control of processing temperature has a crucial impact on the final dimensions, shape, and deformation of the product. The processing temperature depends on the TPU grade and the specific situation of the mold design. The overall trend is that in order to achieve a small shrinkage rate, it is necessary to increase the processing temperature. (TPU crosslinking agent manufacturer)

2. Slow and prolonged holding pressure can lead to molecular orientation. Although smaller product sizes may be obtained, the product undergoes significant deformation and there is a large difference in transverse and longitudinal shrinkage. A large holding pressure can also cause the colloid to be over compressed inside the mold, resulting in a phenomenon where the size of the product after demolding is larger than the size of the mold cavity. (TPU crosslinking agent manufacturer)

3. The position of injection molding speed and pressure conversion should be set accurately. Inaccurate position setting will increase the difficulty of cause analysis, which is not conducive to quick and accurate process adjustment. (TPU crosslinking agent manufacturer)

4. The selection of injection molding machine models should be appropriate. For small-sized injection molded products, it is advisable to choose injection molding machines with smaller models as much as possible in order to increase the injection stroke, facilitate position control, and reasonably convert injection speed and pressure. For example, mobile phone accessories are relatively small in size, while injection molding machines are relatively large. Sometimes, the screw can only advance 1mm and the product is already full of glue, making it impossible to control the position. (TPU crosslinking agent manufacturer)

5. When the moisture content of TPU exceeds 0.2%, it not only affects the appearance of the product, but also significantly deteriorates its mechanical properties, resulting in poor elasticity and low strength of the injection molded product. Therefore, it should be dried at a temperature of 80 ℃ to 110 ℃ for 2-3 hours before injection molding. (TPU crosslinking agent manufacturer)

6. Please enter the title: The cleaning of the injection molding machine barrel should be clean, as minimal mixing of other raw materials can lead to a decrease in the mechanical strength of the product. The material cylinder cleaned with ABS, PMMA, and PE should be cleaned again with TPU nozzle material before injection molding, and residual materials in the cylinder should be removed with TPU nozzle material. When cleaning the hopper, special attention should be paid to the cleaning of a small amount of residual raw materials with other properties at the connection between the hopper and the injection molding machine base, which is easily overlooked by most technical workers in production. (TPU crosslinking agent manufacturer)

Guangyuan Ruifeng New Materials Co., Ltd. is a manufacturer of TPU crosslinking agents. We have mature production processes and are sure to meet your needs.

Keywords: TPU Injection Molding Process - Guangyuan Ruifeng New Materials

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