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How to set the production temperature of TPU injection products
January 07 , 2022

TPU thermoplastic is melted and flowed by heating then cooled to form a certain shape products. Sufficient pressure and good control of the flow state are the keys to produce uniform and excellent physical properties TPU injection products. Compared with PVC and ABS, TPU has a strict processing temperature range. If the temperature is too high, the viscosity will decrease, the resin melt will flow easily to cause undesirable phenomena such as flashing, pores, bumps and shrinkage. If the temperature is too low, the viscosity will increase, the resin melt will flow difficultly, and the products filling will be insufficient.

The temperature that needs to be controlled during the TPU molding process includes barrel temperature, nozzle temperature and mold temperature. The first two temperatures mainly affect the plasticization and flow of TPU, and the latter two temperatures affect the flow and cooling of TPU.

Barrel temperature is related to the hardness of TPU. TPU with high hardness is with high melting temperature, and the maximum temperature at the end of the barrel is also high. The temperature range of the barrel used for processing TPU is 177~232°C. The temperature of the barrel is usually gradually increasing from one side of the hopper (rear end) to the nozzle (front end) , so that the temperature of the TPU rises steadily to plasticized uniformly.

The nozzle temperature is usually slightly lower than the maximum temperature of the barrel to prevent TPU melt salivate. The nozzle temperature also be controlled within the maximum temperature range of the barrel in a self-locking nozzle.

Mold temperature has a great influence on the internal performance and apparent quality of TPU products. The crystallinity of TPU influence mold temperature setting. The mold temperature is usually controlled by a constant cooling medium (such as water). TPU has a high degree of hardness, and high crystallinity the mold temperature is high. For example, 80A hardness TPU, the mold temperature is 20 to 30°C; 91A hardness TPU, the mold temperature is 30 to 50°C;  55D hardnes TPU, the mold temperature is 40 to 65°C. The mold temperature of TPU products is generally 10~60°C. If the mold temperature is low, it is easy to cause a later crystallization which will lead products’ post-shrinkage

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