Hytrel® thermoplastic polyester elastomer is a high performance material with a unique combination of physical properties. Like most elastomers, it has a low flexural modulus (low stiffness), and a high elongation before yield (it stretches a lot before it breaks). However, unlike other elastomers, it has great tear resistance, and extremely high flexural fatigue properties (in other words, you can bang it, bend it, abuse it, whatever, and it still works. Kind of like the old Timex® watch commercial – it takes a licking and keeps on ticking). In addition, it can be processed via a wide variety of methods, including casting, extrusion, blow molding, and injection molding.
This combination of properties makes it well suited for shock absorbing applications. These sketches and prototypes represent the development of “structural cushioning” concepts for use in athletic footwear. While the material is too expensive to be used solely as a cushioning layer, it can provide a substantial performance advantage at a very favorable price - as long as the component is properly designed and engineered.