Polyurethanes can be made ranging from very soft to hard and therefore bridge the gap between rubber and plastics.
By, for example, foaming the polyurethanes, microcellular polyurethane made from harder base materials can replace conventional softer rubber and provide the same elastic resilience and strength.
One advantage is that, unlike rubber, microcellular polyurethane is compressible, i.e., its volume decreases under compressive load. The figure above shows the relationship between polyurethane and rubber, as well as comparisons with other materials to illustrate the possibilities of polyurethane.