1. Molecular structure of TPU

• Raw materials

All TPUs contain the urethane unit: NHCO ₂ , which results from the reaction of isocyanate (NCO) with hydroxyl end groups (OH). They are, as already mentioned, block copolymers with alternating rigid and flexible segments.

• Chemical reactions

• Hard phases, or segments, are created by the reaction of a diisocyanate with a short dialcohol (or glycol) chain (or chain extender) (figure 2 ). This results in a very strong urethane pattern, which is characteristic of hard elements, composed of repeating diisocyanate groups and short dialcohol chains.