TPU Explained

In brief: Thermoplastic polyurethane, or TPU, is a flexible, durable polymer that combines the properties of plastic and rubber. In footwear, expanded TPU beads create lightweight, energy-returning midsole foams, while solid TPU appears in stability elements and waterproof membranes. Because it softens when heated, TPU is recyclable and well suited to heat-welded construction.

What is TPU?

Thermoplastic polyurethane, usually shortened to TPU, is a flexible and durable polymer that sits between plastic and rubber, borrowing useful properties from both. It can be rigid enough to provide structure or soft enough to flex, which makes it one of the most versatile materials in modern footwear. In running and outdoor shoes it shows up in several forms: expanded TPU beads are fused into lightweight, energy-returning midsole foams, while solid TPU is used for stability elements, heel counters and even waterproof membranes. That breadth is what makes TPU so valuable to designers, who can specify the same family of material across very different parts of a shoe. At OD's it features across footwear from Saucony, Salomon and On Running.

How does expanded TPU work as a foam?

The most familiar use of TPU in performance footwear is expanded TPU, often written as eTPU, where the polymer is processed into small beads filled with gas and then fused together into a midsole. The result is a foam that is both lightweight and springy, returning roughly 70 to 75 percent of the energy put into it with each stride. This bead-based construction is the basis of several well-known cushioning systems and helped kick off the modern era of high-rebound midsoles. Because each bead behaves like a tiny cushion, the foam compresses and recovers efficiently, giving a lively underfoot feel that holds up over many miles. It is a versatile foam that balances softness, durability and energy return.

What types of TPU are there?

TPU is not a single material but a family, tuned by chemistry and hardness for different jobs. Polyester-based grades offer high strength, polyether-based grades resist hydrolysis and so handle moisture well, and polycaprolactone-based grades stay flexible in the cold. Hardness is measured on the Shore scale, with footwear TPU ranging from around 60A, which is soft and pliable, up to about 90A, which is firm and structural. This spectrum lets designers dial in exactly the property they need, whether that is a soft, cushioning foam or a rigid stability shank. The same versatility explains why a single shoe might contain several different TPU grades, each chosen for its specific blend of flexibility, strength and durability.

Why is TPU recyclable?

A key advantage of TPU over older thermoset polyurethane is that it is thermoplastic, meaning it softens when heated and hardens again when cooled, with a melting point in the region of 180 to 220 degrees Celsius. This reversible behaviour has two big benefits. First, it enables heat-welded construction, where parts can be bonded without stitching or glue for cleaner, more durable joins. Second, and increasingly important, it makes the material recyclable: where thermoset PU is permanently set once cured, TPU can be reheated and reprocessed. As footwear brands work to reduce waste, that recyclability gives TPU a sustainability edge alongside its performance credentials, allowing offcuts and end-of-life material to be reclaimed rather than landfilled.

TPU at OD's Designer Clothing

At OD's, TPU technology appears throughout our footwear, from energy-returning midsoles to stability elements and waterproof membranes across ranges from Saucony, Salomon and On Running. Because it is so versatile, you will encounter TPU whether you are after a cushioned road shoe, a stable trail runner or a waterproof everyday boot. Our team can explain where it sits in a given shoe and what that means for the feel and durability you can expect. Browse the footwear range online with next-day delivery and free click and collect, or visit our St Helens store to try styles on. Understanding a material like TPU makes it easier to choose a shoe that matches how and where you intend to wear it.