TPU (thermoplastic polyurethane elastomer) is a block polymer with a chemical structure of a hard and soft segment.
The soft section is mainly composed of polyester / polyether / polycaprolactone polyols, which provide the flexibility of the material;
The hard section is mainly aromatic/aliphatic diisocyanate + chain extender, which provides its thermoplasticity, processability and strength.
According to the data, the hard section of TPU has strong hygroscopicity, if it is not fully dried before processing, in the process of high temperature processing, moisture will cause the polymer chain to decompose into amines and carbon dioxide, and eventually it is easy to cause the processed products to appear unsmooth, dull, foamy and foaming and other problems, and the processing process is also unstable, reducing production efficiency.
The decomposition mechanism of TPU in the presence of moisture at high temperatures, from Lubrizol Life Science
Therefore, there will be a dehumidification and drying process before the processing of TPU particles, so that the moisture content of TPU is reduced to a certain limit, and the moisture content of the car coating is < 0.01% according to industry sources.
Osted large-scale dehumidification and drying system
Walter dehumidification and drying system
The process of dehumidification and drying is generally completed by the dehumidification drying system: the air enters the drying barrel after dehumidification and drying, absorbs the moisture of TPU particles, and the moist air is dehydrated through the molecular sieve, and the cycle is reciprocated, and the drying time depends on the dehydration rate according to the need.
