Desmopan® and Texin™ are supplied as natural colored cylindrical or lentil-shaped granules. Depending on the particular grade, the color ranges from transparent/clear and whitish opaque to white. The product can be supplied in quantities of between 25 kg and 1,000 kg, depending on the grade. For sampling purposes 25 - kg sacks or steel drums with a content of 30 kg can be supplied.
Desmopan® and Texin™ should be stored in cool, dry conditions. Temperatures above 40 °C should be avoided. Optimum processing is ensured within approx. 6 months after delivery.
Pretreatment of the granules
TPU absorbs moisture from the air. The extent and rate at which this happens depends on the raw material type, hardness and climate ( Fig. 1).
Fig. 1: Moisture absorption of Desmopan® and Texin™ granules
To ensure trouble-free processing and avoid any loss of quality, we recommend drying to a moisture content of ≤ 0.05 %.
If the granules are too moist, blisters or streaks can occur on the surface of the finished components. The extrudate is no longer smooth and glossy but foamy and gassy.
A frequent cause of defects is also the use of undried functional concentrates. These batches should be separately pre-dried and have a moisture content of ≤ 0.05 %.
Such levels can be reliably reached in conventional dry-air and circulating air dryers (Fig. 2).
(Fig. 2): Operation of a dry-air direr
Depending on the hardness, the recommended drying temperatures are between 80 and 110 °C, with drying times of 1 to 3 hours. Better drying can be achieved in a shorter time with dry-air dryers (Fig. 3).
(Fig. 3): Drying kinetics for Desmopan® and Texin™ granules
Dried, hot granules should not be left to cool down in the open air. They must be stored in dry containers that can be re-sealed. The machine hopper must be kept covered over. Transportation of granules from the dryer to the processing machines is only allowed by means of redried pressurized air.
Additional detailed information for the general drying procedure, possible drying devices, the measuring procedures for residual moisture regulation and an error catalog are available in the following technical information:
PDF/785 KB »
Post-treatment of the finished articles
TPU products attain their optimum physical property llevel only after they have spent some time at room temperature. This process can be speeded up by an annealing process in a circulating air heating oven, reducing it to 15 - 20 hours.
For articles with a hardness of ≤ 92 Shore A, we recommend annealing at 80 - 90 °C, and for a hardness of ≥ 93 Shore A, 100 - 110 °C. The optimum compression set can only be achieved by annealing! The physical data given in our data sheets are always measured on annealed, conditioned test specimens.
Desmopan® and Texin™ are supplied in their natural color and can easily be pigmented, most commonly using color granules (masterbatches), but also using coloring pastes, liquid colors or pure pigments.
Standard commercial equipment can be used to add the colorants and mix them in with the Desmopan® or Texin™. For occasional coloring, use rolling-drum mixers, tumble mixers or similar. It is important to ensure that the colorants and other additives do not contain any moisture. A static mixer in the adapter will significantly improve color dispersion and also reduce the amount of colorant needed.
Color masterbatches provide the simplest, cleanest and most reliable means of coloring Desmopan® and Texin™, particularly when Desmopan® and Texin™ are also the carrier materials. SAN-resin-based color granules are also suitable to a limited extent. Color granules based on polyolefins and PVC are not suitable. Suppliers normally recommend employing metering quantities of between 1.0 and 4.0 % depending on the wall thickness of the articles and the color density of the pigments.
Color pastes, liquid colors and pigments
It is less common to use color pastes, liquid colors and pigments to color Desmopan® and Texin™
because of the more complicated procedure involved. However, there may be benefits in the form of fast color changes and transparent pigmentation. The standard quantities generally range from 0.2 to 1.0 %.
To improve the processing characteristics or specific properties, we recommend the addition of conventional functional concentrates such as:
- antiblocking agents
- release aids
- UV stabilizers
which must also be predried.
Occupational hygiene and environmental information
Desmopan® and Texin™ can be machined and processed over a wide temperature range but, as with all natural and synthetic organic materials, they decompose above a certain temperature. Smoke generation signifies that decomposition is taking place. Slow decomposition commences at approximately 240 °C, depending on the grade of Desmopan® involved. Further information is given in our Safety Data Sheets.
For reasons of occupational hygiene, we recommend efficient air extraction especially when extruding and welding.
Provided that they are not contaminated with other substances, Desmopan® and Texin™ can essentially be disposed of in municipal landfill sites.
They do not constitute a hazard to water. If the material can no longer be recycled, it should be incinerated in a waste incineration plant on account of its high calorific value.