ETPU is a kind of foaming material for shoes.Based on physical foaming method,Noveon makes TPU raw materials completely impregnated in supercritical fluid. Undermine the balance state of polymer/gas homogeneous system inside the material by changing environmental conditions. Then the formation and growth of cell nuclei happens inside the material. Thus, we get the expanded TPU foam material. They can expand 5-8 times compared with original volume because of a lot of gas wrapped inside the microcells. The particles contain a large number of internal microcells with diameters ranging from 30µm to 300µm.The closed-cell, elastic particle foam combines the properties of TPU with the advantages of foams, making it as elastic as rubber but lighter.