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
- 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).