TPU is a block copolymer consisting of alternating sequences of hard and soft segments or domains formed by the reaction of (1) diisocyanates with short-chain diols (so-called chain extenders) and (2) diisocyanates with long-chain diols. By varying the ratio, structure and/or molecular weight of the reaction compounds, an enormous variety of different TPU can be produced. This allows urethane chemists to fine-tune the polymer's structure to the desired final properties of the material.

Properties of commercially available TPU include:

• high abrasion resistance
• low-temperature performance
• high shear strength
• high elasticity
• transparency
• oil and grease resistance
  The currently available TPUs can be divided mainly in two groups, based on soft segment chemistry:
• polyester-based TPUs (mainly derived from adipic acid esters)
• polyether-based TPUs (mainly based on tetrahydrofuran (THF) ethers).