Thermoplastic polyurethanes are demanding high-performance materials that can reach their full potential only by a precise and optimum processing. All process steps in the extrusion of TPU (pre-drying, extrusion, post-treatment such as calibration, cooling, etc.) are associated with a high consumption of energy. Following the recommended processing parameters is very important. The energy efficiency of the processing equipment is of great importance for economic and environmentally friendly processing. Therefore, we recommend paying attention to modern, precise controlling and energy efficient machinery.
Desmopan® and Texin™ grades in the hardness range between 60 Shore A and 70 Shore D are particularly suitable for extrusion applications.
The following products are extruded from them:
- Tubular film
- Flat and blown film
- Blow moldings
The Desmopan® and Texin™ pellets and any functional concentrates must be dried before processing to a moisture content of ≤ 0.05 % (See Sections 2.3 Pretreatment of the granules and 2.5 Coloring)
Conventional thermoplastic processing machines and tools can be used in Desmopan® and Texin™ extrusion. The downstream units must be optimized for the typical properties of TPU.
Blending with regrindand combining of different batches is not recommended.
Single-screw extrudersare normally used for extruding Desmopan® and Texin™. Vented barrels are less suitable.
Heated, grooved feed throats (Fig. 1) ensure higher, more uniform throughput.
Fig. 1: Grooved feed throat
Molten Desmopan® orTexin™ is neither corrosive nor abrasive, which means there is no need for a special steel alloy or armor-plating of the screw.
The drive ratings shown in Fig. 2 should be adhered to. Any additional torque means that processing can be carried out at lower temperatures, making for higher dimensional stability of the emerging melt.
Fig. 2: Minimum drive rating as a Funktion of screw diameter