(A) The first material to dry

No matter what kind of TPU processing, the first thing (and the most important thing) is the appropriate drying of the resin. The TPU used for the extrusion is packed in a steam bag or a sealed bag. It is recommended to process this material at room temperature. Since TPU is a hygroscopic material, it is recommended to pre-dry it. The TPU material should be pre-dried prior to extrusion. The maximum humidity cannot exceed 0.05%. If it exceeds this limit, even if it is a little bit, it can cause damage to the quality of the extruded or injected model product such as the surface is not flat, the nozzle or the residue in the tool is pasted together. Pre-drying this step, should be handled carefully, after drying should avoid re-moisture. Typically, for a resin material that has just been opened, the drying time is 2 to 4 hours. The actual drying time is related to the type of resin, humidity and drying temperature.

(B) Color

All TPU materials can be blended by mixing the pigment or color master batch. It is also possible to easily achieve color matching by using a color-based master-based color patch. Usually the amount of color master batch accounted for 2%. Non-TPU-based master batches are usually incompatible and may cause other problems such as pigment dispersion, uneven surface, color brightness, and so on.

(C) Processing temperature

The extruder cartridge should be divided into at least three temperature control zones and a temperature controller for the converter and eye mold. The thermocouple and controller for controlling these sections should be checked regularly. Most modern extruders have more heating zones. For the TPU, it is important to make precise and consistent settings for all the extrusion parameters. A voltage-controlled temperature controller should be used because the on / off controller can cause temperature fluctuations greater than 5F. Temperature fluctuations will lead to uneven thermal index, will make the size of the extrusion products are biased. Especially in the measurement area, the adapter, and the mold at the temperature of some fluctuations will lead to extrusion rate and quality.

For TPU (Shore hardness A80, A90), the temperature of the feed section should be set at 165C and the temperature of the metering zone should be set at 185C. The nozzle / eye mold temperature is low 5C, such as 180C. The high temperature will cause the molecular weight to be degraded, leading to degradation of its mechanical properties.