Key Considerations for TPE Extrusion Molding Process
Time of issue:2024-12-28
Extrusion molding is a versatile, highly productive, adaptable, and widely used molding method in the field of polymer material processing, occupying the largest proportion among all molding techniques. It is suitable for all polymer materials. Plastic extrusion molding, also known as extrusion or extrusion molding, can form almost all thermoplastics and can also be used for a few thermosetting plastics, such as phenolic resin, but the variety of extrudable thermosetting plastic products is limited. Products extruded from plastics include pipes, sheets, rods, films, monofilaments, cable coatings, various profiled materials, and composites of plastics with other materials. Next, a TPE extrusion molding wholesaler will discuss the issues that should be noted during extrusion molding:
- Drying TPE Material Before Extrusion
Generally, materials should be dried at 80°C for 2 hours or tray-dried at 100°C for 1 hour. Note that the thickness of the material layer should not exceed 5 cm for optimal results. When the surface of the extruded profile is not smooth, has bubbles, or is prone to cracking, it can be determined that the raw material contains too much moisture.
- Using Low-Temperature Extrusion When Possible
While ensuring the quality of plasticization, try to reduce the extrusion temperature as much as possible. When the surface of the extrudate has a uniform color and a slight shine upon exiting the die, it can be determined that the plasticization effect is good. If the surface of the extrudate coming out of the die is very bright, the extrusion temperature can be appropriately reduced.
- Temperature Setting in a Parabolic Pattern
The temperature in the middle section of the screw is the highest, slightly lower in the feeding section, and slightly lower in the die head. Special attention should be paid to the fact that the die head temperature setting is also related to the die head length (the distance from the top of the screw to the die head outlet). If the distance is long, the die head temperature should be set slightly lower than the middle section temperature, such as 10~20°C lower. If the distance is short, the die head temperature can be set 30~50°C lower than the middle section temperature. Typical temperature settings are 150~170°C (feeding), 170~180°C (middle section), 190~200°C (front section), and 180°C (nozzle). These temperature settings are only for reference, and specific temperatures can be adjusted according to the specific physical properties of different TPE and TPR materials (it is recommended to consult the raw material supplier). If extrusion instability or low melt strength is observed, adjustments can be made according to point 2.
- Cleaning the Die Head Before Changing Materials
Even if it is the same brand of raw material, if it is found that the raw material is not well-dried, the die head must be cleaned after redrying and before extrusion. If the extrudate is not smooth, unstable, or prone to breaking after changing materials, the die head needs to be disassembled and cleaned.
- Gradually Increasing the Extrusion Speed
Setting the extrusion speed too fast can easily cause extrusion instability. Try to adjust the extrusion speed in intervals of 3~5 minutes until the desired speed is reached.
These are the five key points for the TPE extrusion molding process. Additionally, melt strength is not only related to the extrusion temperature setting but may also be related to the TPE material itself. Regarding extrusion temperature setting, the molecular weight of SEBS and SBS in the compounded system is an important influencing factor. Moreover, materials based on SEBS require higher extrusion temperatures than those based on SBS.
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